Database: EMBASE <: international biomedical and pharmaceutical literature, 1988 - May 2000. [Trial access until 3/2001. Feedback welcome to medical.library@umich.edu] Search Strategy (You Saved Citations 1-83 From Set 64): ----------------------------------------------------------------------------- 1 exp Trace element/ 4457 2 Arsenic/ 2390 3 Boron/ 782 4 Chromium/ 4462 5 Cobalt/ 4108 6 Copper/ 12377 7 Fluorine/ 722 8 Iodine/ 2620 9 Manganese/ 6381 10 Molybdenum/ 1341 11 Nickel/ 5956 12 Selenium/ 5191 13 Silicon/ 1509 14 Tin/ 653 15 Vanadium/ 1214 16 Zinc/ 14450 17 or/1-16 47342 18 exp Tooth demineralization/ 7492 19 demineralization.mp. 879 20 caries.mp. 1798 21 caires.mp. 0 22 craies.mp. 0 23 careis.mp. 1 24 carise.mp. 0 25 (teeth adj3 cavit:).mp. 32 26 (tooth adj3 cavit:).mp. 97 27 (dental adj3 cavit:).mp. 85 28 (dentin adj3 cavit:).mp. 19 29 (enamel adj3 cavit:).mp. 10 30 (teeth adj3 decay:).mp. 58 31 (tooth adj3 decay:).mp. 58 32 (dental adj3 decay:).mp. 47 33 (dentin adj3 decay:).mp. 0 34 (enamel adj3 decay:).mp. 1 35 (active adj decay).mp. 5 36 (rampant adj3 decay:).mp. 4 37 (recurrent adj3 decay:).mp. 5 38 (white adj spot:).mp. 231 39 carious.mp. 109 40 cariology.ti,ab. 2 41 (non-cavitated adj3 lesion:).mp. 0 42 (noncavitated adj3 lesion:).mp. 1 43 Tooth remineralization/ 788 44 (dental adj3 fissure:).mp. 14 45 (tooth adj3 fissure:).mp. 8 46 (teeth adj3 fissure:).mp. 1 47 caries-free.mp. 29 48 cariesfree.mp. 0 49 Cariogenic agents/ 3 50 precavit:.mp. 2 51 (filled adj3 teeth).mp. 45 52 (filled adj3 tooth).mp. 9 53 (oral adj fissure:).mp. 17 54 (tooth adj3 remineraliz:).mp. 1 55 (teeth adj3 remineraliz:).mp. 5 56 dft.mp. 542 57 dfs.mp. 980 58 dmf:.mp. 1235 59 cariogeni:.mp. 164 60 or/18-59 12313 61 17 and 60 148 62 limit 61 to human 65 63 from 62 keep 1-65 65 64 61 not 62 83 65 from 64 keep 1-83 83 *************************** <1> UI - 2000167079 AU - Liang Y AU - Luo S AU - Liu C AU - Wu X AU - Ma Y IN - Y. Ma, Natl. Lab. Applied Organic Chemistry, Lanzhou University, Lanzhou 730000; China. E-Mail: mayx@lzu.edu.cn. TI - Stereoselective Heck-type cross-coupling reactions of iodine heterocyclic compounds with olefins. SO - Tetrahedron Vol 56(19) (pp 2961-2965), 2000. AB - Polyfunctional molecules are prepared by a modified stereoselective Heck-type cross-coupling reaction between iodine heterocyclic compounds and olefins in DMF using Pd(OAc)2 as a catalyst in the presence of bases (Na2CO3 or K2CO3). This coupling reaction proceeds smoothly at room temperature and gave coupling products in high yields. (C) 2000 Elsevier Science Ltd. [References: 14] <2> UI - 2000166432 AU - Piers E AU - McEachern EJ AU - Burns PA IN - E. Piers, Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1; Canada. E-Mail: epier@interchange.ubc.ca. TI - Cu(I)-mediated intramolecular conjugate addition of alkenyltrimethylstannane functions to alpha,beta-unsaturated ketones: A convenient preparation of functionalized cis-fused bicyclo[4.3.0]non-8-en-3-ones and Bicyclo[3.3.0]oct-6-en-3-ones. SO - Tetrahedron Vol 56(18) (pp 2753-2765), 2000. AB - A new copper(I)-mediated method for effecting intramolecular conjugate addition of alkenyl functions to alpha,beta-unsaturated ketone systems is reported. Treatment of the substrates 14, 15, 19-21, 22 and 23 with 2.5 equiv. of CuCl in DMF at room temperature affords excellent yields of the corresponding bicyclic ketones 24, 25, 29-31, 32 and 33. On the other hand, treatment of substances 15-18 with CuCN in DMSO at 60 [degree] C provides good-to- excellent yields of the corresponding bicyclic products 25-28. (C) 2000 Elsevier Science Ltd. [References: 31] <3> UI - 2000119987 AU - Schmid R AU - Ziegler T IN - T. Ziegler, University of Calgary, Dept. of Chemistry, 2500 University Drive N.W., Calgary, Alta. T2N 1N4; Canada. TI - Ethylene-polymerization by surface supported Cr(IV) species: Possible reaction mechanisms revisited by theoretical calculations. SO - Canadian Journal of Chemistry Vol 78(2) (pp 265-269), 2000. AB - Possible reaction mechanisms of olefin polymerization catalyzed by surface supported Cr(IV) species have been investigated by first principles density functional theory (DFT). Pathways starting from neutral alkylidene or bisalkyl complexes were found to suffer from high ethylene insertion barriers, whereas a cationic system formed by protonation of the alkylidene show a low barrier for chain propagation. [References: 30] <4> UI - 2000103214 AU - Saleh MA AU - Ewane E AU - Jones J AU - Wilson BL IN - M.A. Saleh, Envtl. Chemistry/Toxicology Lab., Department of Chemistry, Texas Southern University, Houston, TX 77004; United States. TI - Monitoring Wadi El Raiyan lakes of the egyptian desert for inorganic pollutants by ion-selective electrodes, ion chromatography, and inductively coupled plasma spectroscopy. SO - Ecotoxicology & Environmental Safety Vol 45(3) (pp 310-316), 2000. AB - Wadi El Raiyan is a great depression located southwest of Cairo in the western desert of Egypt, one of the most arid regions of the world. In 1973, Wadi El Raiyan was connected with the agricultural wastewater drainage system of the El Faiyum province to provide a reservoir for the wastewater that exceeded the capacity of Lake Qarun north of the province. Pollutants from agricultural waste including pesticides and fertilizers as well as other effluents of industrial activities and runoffs certainly will pass into the biotic elements of the ecosystem. This report presents the status of inorganic pollutants including unions, carious, and trace metals in the two lakes and the surrounding springs of Wadi El Raiyan using ion chromatography, ion-selective electrodes, and inductively coupled plasma emission spectroscopy. The report also includes the levels of selected metals in the vegetation community of the area. The result of this investigation revealed a great improvement in water quality of the Wadi El Raiyan lakes compared to 1988 report by Saleh et al. Mercury was not detected in any of the samples and the level of lead was significantly reduced. Cadmium levels were much higher than those seen earlier. The higher level of cadmium might be used as an indicator to track the contamination of water by human waste. Concentrations of common anions were not significantly different from those reported earlier. However, an increase in the level of cyanide was observed. Levels of heavy metals in vegetation around the lakes were also found to be lower than previously reported. (C) 2000 Academic Press. [References: 19] <5> UI - 2000081528 AU - Eddaoudi M AU - Li H AU - Yaghi OM IN - O.M. Yaghi, University of Michigan, Ann Arbor, MI 48109-1055; United States. TI - Highly porous and stable metal-organic frameworks: Structure design and sorption properties. SO - Journal of the American Chemical Society Vol 122(7) (pp 1391-1397), 2000. AB - Gas sorption isotherm measurements performed on the evacuated derivatives of four porous metal-organic frameworks (MOF-n), Zn(BDC).(DMF)(H2O) (DMF = N,N'-dimethylformamide, BDC = 1,4- benzenedicarboxylate) (MOF-2), Zn3(BDC)3.6CH3OH (MOF-3), Zn2(BTC)NO3.(C2H5OH)5H2O (BTC = 1,3,5-benzenetricarboxylate) (MOF-4), and Zn4O(BDC)3.(DMF)8C6H5Cl (MOF-5), reveal type I isotherms for n = 2, 3, and 5, which is evidence of microporous and accessible channels having high structural integrity and organization. Although gas sorption into MOF-4 was not observed, careful examination of its ethanol sorption isotherms at 22 and 32 [degree] C point to the presence of coordinatively unsaturated zinc centers within its pores, which upon ethanol sorption undergo coordination transitions from 3- to 4-, 4- to 5-, and 5- to 6-coordination. MOF-n materials were produced by building the extended analogues of molecular metal carboxylate clusters - a strategy that has allowed the realization of the most porous and thermally stable framework yet reported: the evacuated form of MOF-5 is especially stable in air at 300 [degree] C and has a free pore volume representing 55-60% of its crystal as determined by gas sorption and single- crystal diffraction studies. <6> UI - 2000062763 AU - Peng S AU - Qing F-L AU - Li Y-Q AU - Hu C-M IN - F.-L. Qing, Lab. of Organofluorine Chemistry, Shanghai Inst. of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032; China. E-Mail: FLQ@pub.sioc.ac.cn. TI - Palladium(0)/copper(I)-cocatalyzed cross-coupling of the zinc reagent of ethyl 3-bromo-3,3-difluoropropionate with aryl (alkenyl) halides: An efficient stereoselective synthesis of beta-fluoro-alpha,beta-unsaturated esters. SO - Journal of Organic Chemistry Vol 65(3) (pp 694-700), 2000. AB - Ethyl 3-bromo-3, 3-difluoropropionate was prepared in an overall yield of 75% from the radical addition of dibromodifluoromethane to ethyl vinyl ether under Na2S2O4 initiation, followed by oxidation of the acetal with Caro acid. The treatment of 1 with active zinc dust in anhydrous DMF at room temperature produced the zinc reagent ZnBrCF2CH2CO2C2H5 (2). The cross coupling of the zinc reagent 2 with aryl (alkenyl) halides (R-X) in DMF using Pd(0)-Cu(I) as cocatalyst stereoselectively provided the beta-fluoro-alpha,beta- unsaturated esters (RCF=CHCO2C2H5 4) directly and in moderate yields. An E/Z ratio ranging from 3:2 to 1:0 was observed. This is the first example that Cu(I) can improve the selectivity of the cross-coupling reaction. Mechanistic studies revealed that zinc reagent 2 underwent stereoselective elimination to produce (Z)-1-fluoro-2-(ethoxycarbonyl)ethenylzinc reagent 6, and then the cross-coupling of 6 with aryl(alkenyl) halides under palladium(O) catalysis afforded the beta-fluoro-alpha,beta-unsaturated esters 4. <7> UI - 2000029084 AU - Tobin WR AU - Greene RS IN - Dr. W.R. Tobin, Department of Biological Sciences, State University New York at Buffalo, 109 Cooke Hall, Buffalo, NY 14260; United States. E-Mail: wtobin@rocketmail.com. TI - Mese-substituted cationic porphyrins interact with dsDNA and exhibit different localization patterns in radiation-induced fibrosarcoma cells. SO - Anticancer Research Vol 19(4 B) (pp 2953-2958), 1999. AB - Meso-substituted cationic porphyrins were examined for binding dsDNA. Subcellular localization time studies used Confocal Laser Scanning Microscopy of radiation-induced fibrosarcoma (RIF) cells incubated with porphyrins. Binding studies revealed a reversible interaction between porphyrin and dsDNA that is a funtion of DNA shape. Binding was inhibited at high salt concentrations, and enhanced by heat and DNA denaturants such as dimethyl formamide (DMF). Trans dicationic porphyrin required more stringent binding conditions than cis dicationic and tetracationic porphyrins. Phenol extraction of porphyrin from the DNA-porphyrin complex demonstrates that cationic porphyrins do not damage dsDNA at high concentrations. Localization studies within a 24-hour range reveal different distribution patterns. Metal chelates of tetracationic porphyrin exhibited a cytoplasmic localization with the exception of the zinc chelate. Localization of other metal chelates appears to be redistributed to lysosomes and mitochondria between 3 and 6 hours post-incubation. HPPH used in PDT clinical trials localizes to the cytoplasmic compartment. [References: 25] <8> UI - 2000011080 AU - Wilson N AU - Quigley R AU - Mansoor O IN - Dr. N. Wilson, 367A Karori Road, Karori, Wellington; New Zealand. E-Mail: nwilson@actrix.gen.nz. TI - Food ads on TV: A health hazard for children?. SO - AUST NEW ZEALAND J PUBLIC HEALTH, Vol 23(6) (pp 647-650), 1999. AB - Objective: To examine the nutritional quality of food in television food advertisements that are targeted at children. Method: We videotaped 42 hours of children's programs and analysed the food advertisements' content and nutrient composition using the New Zealand Food Composition Database. Results: Of 269 food advertisements, 63% were for foods 'high in fat and/or sugar'. Children who ate only the advertised foods would eat a diet too high in fat, saturated fat, protein, free sugars and sodium. Furthermore, their diets would have suboptimal levels of fibre and suboptimal intakes of a number of important micronutrients (depending on age), including magnesium, selenium and vitamin E. The food products advertised on this channel rarely included nutritious low-cost foods that are necessary for food security in low-income groups. There were also no food advertisements that included any of the healthy foods consumed by Maori and Pacific peoples. Conclusions: Food advertisements targeted at children generally reflect the dietary pattern associated with an increased risk of obesity and dental caries in childhood; and cardiovascular disease, diabetes and cancers in adulthood. [References: 25] <9> UI - 1999369558 AU - Tachev A AU - Jordanova J AU - Getchev V AU - Zlateva St TI - Determination of fluorine in toothpastes by thin layer and gas chromatography. [Bulgarian] SO - KHIG ZDRAVEOPAZ, Vol 41(2-3) (pp 49-51), 1998. AB - Toothpastes are among the most widely used means for hygiene of the oral cavity. Due to the modern requirements for their safely, the ingredients of toothpastes are subjected to strict hygienic control. Fluorine compounds are used as active anti-caries ingredients. Their content is regulated by our sanitary legislation in concentrations up to 0.15% (calculated as water- soluble fluorine). This imposes its quantitative determination at sanitary control of toothpastes. A gas chromatography method with high sensitivity and easy application is developed for direct determination of water-soluble fluorine in toothpastes. A thin-layer chromatography method with sensitivity for identification and determination of sodium monofluorine phosphate in toothpastes is proposed. [References: 7] <10> UI - 1999369146 AU - Maruo N AU - Uchiyama M AU - Kato T AU - Arai T AU - Akisada H AU - Nishino N IN - N. Nishino, Department of Applied Chemistry, Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550; Japan. E-Mail: nishino@che.kyutech.ac.jp. TI - Hemispherical synthesis of dendritic poly(L-lysine) combining sixteen free-base porphyrins and sixteen zinc porphyrins. SO - Chemical Communications Vol 5(20) (pp 2057-2058), 1999. AB - Dendritic poly(L-lysine) combining sixteen free-base porphyrins and sixteen zinc porphyrins hemispherically at the fifth generation was successfully synthesised and showed intramolecular fluorescence energy transfer in DMF. [References: 9] <11> UI - 1999362692 AU - Davis DS AU - Shadinger SC IN - D.S. Davis, Department of Chemistry, Mercer University, 1400 Coleman Avenue, Macon, GA 31207; United States. TI - Sodium methylthiolate as an efficient deprotecting agent for dicobalt hexacarbonyl complexes of acetylenes. SO - Tetrahedron Letters Vol 40(44) (pp 7749-7752), 1999. AB - Various dicobalt hexacarbonyl acetylene complexes were efficiently converted to the unprotected acetylene by the reaction of two molar equivalents of sodium methylthiolate. Yields and reaction times depend upon the choice of solvent. DMF proved to be the most efficient solvent, with the reaction proceeding at >80% conversion in 5 minutes at room temperature. [References: 10] <12> UI - 1999280437 AU - Braga D AU - Grepioni F AU - Tedesco E AU - Calhorda MJ AU - Lopes PEM IN - D. Braga, Dipartimento di Chimica G. Ciamician, Universita di Bologna, Via Selmi 2, 40126 Bologna; Italy. TI - The effect of the counter ion on M - H...H - X (X = O, N) interactions in crystalline transition metal hydrides. SO - NEW J CHEM, Vol 23(2) (pp 219-226), 1999. AB - The relationship between molecular and crystal structures of organometallic complexes showing intramolecular interactions of the M - H...H - X type (M = transition metal, X = O, N, and S) has been investigated by a combined use of molecular orbital calculations and crystal packing analysis. Molecular and crystal structures determined by neutron and/or X-ray diffraction data of coordination complexes and clusters showing intramolecular (M - H...H - X) interactions within the range 1.5-2.5 [Angstrom] have been retrieved from the Cambridge Structural Database. DFT calculations were performed for the majority of compounds in order to determine the nature of the H...H interaction. The optimized geometries obtained by DFT are usually in good agreement with the experimentally determined ones, short H...H distances being also found. Most of the systems analysed, such as cis-[IrH(OH)(PMe3)4][PF6], involve cationic complexes. It has been found that the counter ion exerts a strong influence in bringing together the two hydrogens. When it is included in the calculations, the agreement between the observed and the calculated structures is much better. [References: 34] <13> UI - 1999280430 AU - Manteghetti A AU - Belin C AU - Tillard-Charbonnel M AU - Pascal J-L AU - Clot E AU - Favier F IN - F. Favier, Lab. Agregats Molec. Mat. Inorgan., CNRS ESA 5072, Universite Montpellier II, 34095 Montpellier Cedex 5; France. E-Mail: pasfav@univ-montp2.fr. TI - Conformational preferences of bis(acetonitrile)tetrachloro molybdenum(IV) and tungsten(IV). Crystal structure of WCl4(CH3CN)2 and DFT calculations. SO - NEW J CHEM, Vol 23(2) (pp 165-171), 1999. AB - Crystalline MoCl4(NCCH3)2 and WCl4(NCCH3)2 have been obtained by an electrocrystallization process and are shown to be isostructural. They crystallize in the monoclinic space group C2 with a = 11.668(3), b = 7.616(5), c = 5.901(2) [Angstrom], beta = 103.04(3) [degree] and a = 11.679(2), b = 7.631(3), c = 5.896(2) [Angstrom], beta = 103.11(2) [degree], respectively. The structure of the tungsten compound determined on a single crystal was refined to a final R(F2) value of 0.046 [R(w)(F2) = 0.112] using 745 observed reflections. The metal is in a distorted octahedral environment with 4 chlorine atoms in the equatorial plane and 2 acetonitrile groups in axial positions. DFT optimization of the geometry was done at the B3LYP/LANLD1Z/LANLD2Z/6-31G*/6- 31G** and BPW91/LANLD1Z/LANLD2Z/6-31G*/6-31G** levels of theory for singlet and triplet spin states for WCl4(NCCH3)2 in cis and trans conformations, and for WCl4(NCCH3)(x) (X = 1 or 2) with an eta2 coordination of acetonitrile. At the two levels, the energy minimum corresponds to the trans structure with a triplet spin state. The electronic spectra were assigned and the vibrational, 13C and 1H NMR spectroscopies confirm that the previously reported cis and eta2 structures are incorrect. [References: 36] <14> UI - 1999260329 AU - Zohouri FV AU - Rugg-Gunn AJ IN - A.J. Rugg-Gunn, Department of Child Dental Health, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4BW; United Kingdom. TI - Fluoride concentration in foods from Iran. SO - International Journal of Food Sciences & Nutrition Vol 50(4) (pp 265-274), 1999. AB - Knowledge of fluoride intake is important in optimizing the caries-preventive role of fluoride, and the measurement of fluoride intake usually requires information on the fluoride concentration in foods and drinks. Most information comes from developed countries and there are no data on fluoride concentration in foods in Middle Eastern countries including Iran. The aim of the study was to: (a) describe a modification to the silicon-facilitated diffusion method for determining fluoride concentration, (b) provide information on fluoride content of foods in Iran to supplement food tables for the Middle East, and (c) determine the effect of variation in the fluoride concentration of drinking water on the fluoride concentration of prepared foods. Five hundred and ten samples of 84 popular foods and drinks were collected from three areas of Iran where water fluoride concentrations were 0.32, 0.58 and 4.05 mg/L. The mean recovery of fluoride added to food samples before diffusion was 98 +/- 5%. Values for duplicate analysis of 20 food samples were within 0.03 mug F/g. Most of the samples of foods and drinks came from the area with 0.32 mg F/L in water supplies. For 30 of the 84 items, fluoride concentration was below 0.1 mug/g. Fluoride concentrations in the cereals group (which constituted much of the diet) were mainly between 0.2 and 0.3 mug/g, when prepared for consumption. It was concluded that: (a) modification of a published method for determining fluoride concentration of foods appeared to be an advance, (b) values for fluoride concentration of foods commonly consumed in Iran showed variation between groups but were in broad agreement with published data, and (c) concentration of fluoride in water influences positively fluoride concentration in foods cooked in water, but the increase in foods was less than the increase in fluoride concentration in water. [References: 29] <15> UI - 1999226005 AU - Cini R IN - R. Cini, Department of Chemical, Biosystem Sciences and Technologies, University of Siena, Pian dei Mantellini 44, I-53100 Siena; Italy. E-Mail: cini@unisi.it. TI - Molecular orbital study of complexes of zinc(II) with sulphide, thiomethanolate, thiomethanol, dimethylthioether, thiophenolate, formiate, acetate, carbonate, hydrogen carbonate, iminomethane and imidazole. Relationships with structural and catalytic zinc in some metallo-enzymes. SO - Journal of Biomolecular Structure & Dynamics Vol 16(6) (pp 1225-1237), 1999. AB - Geometry optimization and energy calculations have been performed at the density functional B3LYP/LANL2DZ level on hydrogen sulfide (HS-), dihydrogensulfide (H2S), thiomethanolate (CH3S-), thiomethanol (CH3SH), thiophenolate (C6H5S-), methoxyde (CH3O-), methanol (CH3OH), formiate (HCOO-), acetate (CH3COO-), carbonate (CO32-), hydrogen carbonate (HCO3-), iminomethane (NH=CH2), [ZnS], [ZnS2]2-, [Zn(HS)]+, [Zn(H2S)]2+, [Zn(HS)4]2-, [Zn(CH3S)]+, [Zn(CH3S)2], [Zn(CH3S)3]- , [Zn(CH3S)4]2-, [Zn(CH3SH)]2+, [Zn(CH3SCH3)]2+, [Zn(C6H5S)]+, [Zn(C6H5S)2], [Zn(C6H5S)3]-, [Zn(HS)(NH=CH2)2]+, [Zn(HS)2(NH=CH2)2], [Zn(HS)(H2O)]+, [Zn(HS)(HCOO)], [Zn(HS)2(HCOO)]-, [Zn(CH3O)]+, [Zn(CH3O)2], [Zn(CH3O)3]-, [Zn(CH3O)4]2, [Zn(CH3OH)]2+, [Zn(HCOO)]+, [Zn(CH3COO)]+, [Zn(CH3COO)2], [Zn(CH3COO)3]-, [Zn(CO3)], [Zn(HCO3)]+, and [Zn(HCO3)(Imz)]+ (Imz, 1,3-imidazole). The computed Zn-S bond distances are 2.174 [Angstrom] for [ZnS], 2.274 for [Zn(HS)]+, 2.283 for [Zn(CH3S)]+, and 2.271 for [Zn(C6H5S)]+, showing that sulfide anion forms stronger bonds than substituted sulfides. The nature of the substituents on sulfur influences only slightly the Zn-S distance. The optimized tetra-coordinate [Zn(HS)2(NH=-CH2)2] molecules has computed Zn-S and Zn-N bond distances of 2.392 and 2.154 [Angstrom] which compare well with the experimental values at the solid state obtained via X-ray diffraction for a number of complex molecules. The computed Zn-O bond distances for chelating carboxylate derivatives like [Zn(HOCOO)]+ (1.998 [Angstrom] ), [Zn(HCOO)]+ (2.021), and [Zn(CH3COO)]+ (2.001) shows that the strength of the bond is not much influenced by the substituent on carboxylic carbon atom and that CH3- and HO- groups have very similar effects. The DFT analysis shows also that the carboxylate ligand has a preference for the bidentate mode instead of the monodentate one, at least when the coordination number is small. The analysis of the bond formation energies for the species Zn(CH3S)(n) shows that the addition of a CH3S- ligand to the zinc(II) center is highly exothermic for Zn2+ (-415.26 kcal/mol), for [Zn(CH3S)]+ (-207.06) and for [Zn(CH3S)2] (-67.09). Interestingly, the formation of tetrahedral [Zn(CH3S)4]2- from tri-coordinate [Zn(CH3S)3]- is endothermic by 32.56 kcal/mol. This unfavorable enthalpy contribution for the stability of the tetra-coordinate species suggests a facile methylation of one of the sulfur atoms at the ZnS4 core. <16> UI - 1999194577 AU - Yoshida K AU - Tanagawa M AU - Kamada K AU - Hatada R AU - Baba K AU - Inoi T AU - Atsuta M IN - Dr. K. Yoshida, Department of Fixed Prosthodontics, Nagasaki Univ. School of Dentistry, 1-7-1, Sakamoto, Nagasaki 852-8588; Japan. E-Mail: keiichi@net.nagasaki-u.ac.jp. TI - Silica coatings formed on noble dental casting alloy by the sol-gel dipping process. SO - Journal of Biomedical Materials Research Vol 46(2) (pp 221-227), 1999. AB - The sol-gel dipping process, in which liquid silicon alkoxide is transformed into the solid silicon-oxygen network, can produce a thin film coating of silica (SiO2). The features of this method are high homogeneity and purity of the thin SiO2 film and a low sinter temperature, which are important in preparation of coating films that can protect from metallic ion release from the metal substrate and prevent attachment of dental plaque. We evaluated the surface characteristics of the dental casting silver-palladium- copper-gold (Ag-Pd-Cu-Au) alloy coated with a thin SiO2 film by the sol-gel dipping process. The SiO2 film bonded strongly (over 40 MPa) to Ti-implanted Ag-Pd-Cu-Au alloy substrate as demonstrated by a pull test. Hydrophobilization of Ti-implanted/SiO2-coated surfaces resulted in a significant increase of the contact angle of water (80.5 [degree] ) compared with that of the noncoated alloy specimens (59.3 [degree] ). Ti-implanted/SiO2-coated specimens showed the release of many fewer metallic ions (192 ppb/cm2) from the substrate than did noncoated specimens (2,089 ppb/cm2). The formation of a thin SiO2 film by the sol-gel dipping process on the surface of Ti- implanted Ag-Pd-Cu-Au alloy after casting clinically may be useful for minimizing the possibilities of the accumulation of dental plaque and metal allergies caused by intraoral metal restorations. [References: 32] <17> UI - 1999183065 AU - Spatafora GA AU - Moore MW IN - Dr. G.A. Spatafora, Department of Biology, Middlebury College, Middlebury, VT 05753; United States. E-Mail: spatafor@panther.middlebury.edu. TI - Growth of Streptococcus mutans in an iron-limiting medium. SO - Methods in Cell Science Vol 20(1-4) (pp 217-221), 1998. AB - Microbial pathogens require iron to survive and promote disease. Reports in the literature indicate that iron can potentiate infection in the human host by triggering the expression of bacterial virulence determinants. Streptococcus mutans is a prevalent microorganism in dental plaque and the principal causative agent of human dental caries. This oral pathogen may respond to the changing availability of iron in the plaque environment brought about by conditions of feast or famine. Our understanding of a role for iron in S. mutans-induced caries formation is limited, however, by the lack of an appropriate test medium. In this study we applied batch chromatography to remove iron from a chemically-defined medium which we subsequently reconstituted with manganese and/or magnesium. The final metal ion concentrations in this medium were confirmed by inductively coupled argon plasma (ICAP) analysis. Importantly, the iron-depleted medium supported the growth of S. mutans only when supplemented with 0.01 to 10 muM iron, concentrations which are consistent with those found in human saliva. The practical applications of this medium are far-reaching and include the identification of iron sources, and iron-responsive genes and their products which may promote streptococcal pathogenesis. Other trace metals may be altered in this medium to promote investigations of their putative effect(s) on streptococcal growth and expression. [References: 9] <18> UI - 1999176579 AU - Feng C-C AU - Nandi M AU - Sambaiah T AU - Cheng C-H IN - C.-H. Cheng, Department of Chemistry, National Tsing Hua University, Hsinchu 30043; Taiwan. TI - Nickel-catalyzed highly stereoselective ring opening of 7-oxa- and azanorbornenes with organic halides. SO - Journal of Organic Chemistry Vol 64(10) (pp 3538-3543), 1999. AB - Nickel-catalyzed ring-opening reactions of 7-heteroatom norbornadienes and norbornenes with various organic halides to give products with multiple stereocenters are described. Treatment of 7-oxabenzonorbornadiene (1a) and 7- carbomethoxy-7-azabenzonorbornadiene (1b) with aryl iodides (ArI) in the presence of NiCI2(PPh3)2 and Zn powder gave the corresponding ring- opening addition products cis-1,2-dihydro-2-aryl-1-naphthol (2a-m) and methyl N-[cis-1,2-dihydro-2-aryl-1-naphthyl]carbamate (3a-e) completely stereoselectively in 40-99% yields. The nickel system also catalyzes the reaction of highly substituted oxabicyclic [2.2.1] compounds (1c-e) with organic halides (PhI, PhCH2Br, PhCHCHBr, and PhCBrCH2) to give the corresponding ring-opening products (4a-d, 5, 6a,b) that consist of four fixed stereocenters. Studies on the effect of solvent on the reaction of 1a with PhI show that CH3CN gives the highest yield of product 2a; no product 2a is observed when toluene, dichloromethane, methanol, DMF, or DMSO is used as solvent. Addition of extra PPh3 to the reaction mixture reduced the yield of 2a. A mechanism is proposed to account for the formation of these nickel- catalyzed ring-opening addition products. <19> UI - 1999170721 AU - Sampath Kumar HM AU - Anjaneyulu S AU - Subba Reddy BV AU - Yadav JS IN - H.M. Sampath Kumar, Organic Division-I, Indian Inst. of Chemical Technology, Hyderabad-500 007; India. TI - Zinc mediated allylation of azides: A novel method for the high yield preparation of N-allylamines. SO - SYNLETT, Issue 5 (pp 551-552), 1999. AB - A quick and efficient approach for mono N-allylamines has been developed by the reaction of allyl zinc reagent with alkyl and aryl azides in DMF. <20> UI - 1999162002 AU - Salzmann R AU - McMahon MT AU - Godbout N AU - Sanders LK AU - Wojdelski M AU - Oldfield E IN - E. Oldfield, Department of Chemistry, University of Illinois, 600 South Mathews Avenue, Urbana, IL 61801; United States. TI - Solid-state NMR, crystallographic and density functional theory investigation of Fe-CO and Fe-CO analogue metalloporphyrins and metalloproteins. SO - Journal of the American Chemical Society Vol 121(16) (pp 3818-3828), 1999. AB - We have synthesized and characterized the following four metalloporphyrins: Fe(OEP)(CO)(1-MeIm), Ru(OEP)(CO)(1-MeIm), Os(OEP)(CO)(1- MeIm), and Fe(TPP)(iPrNC)(1-MeIm), where OEP = 2,3,7,8,12,13,17,18- octaethylporphyrinate, TPP = 5,10,15,20-tetraphenylporphyrinate, and 1-MeIm = 1-methylimidazole, using single-crystal X-ray diffraction, solid-state nuclear magnetic resonance (NMR), and density functional theory (DFT) methods. Unlike the situation found with the Fe-, Ru-, Os(TPP)(CO)(1-MeIm) analogues, which have ruffled porphyrins, all four systems here have essentially planar porphyrin rings, and a rule is developed that successfully predicts the presence or absence of ring distortion in a broad range of metalloporphyrins. In each of the three CO complexes, the M-C-O bond is close to linear and untilted, but with the iPrNC adduct, there are noticeable ligand distortions supporting the idea that RNC groups (but not CO) may be distorted in metalloproteins. Solid-state 13C, 15N, and 17NMR shifts and shifts and tensors determined experimentally are in generally good agreement with those computed via DFT. For isocyanide binding to proteins, the experimental shifts are more deshielded than in the model system, and the effects which might contribute to this difference are explored theoretically. Unlike CO, electrostatic field effects are unlikely to make a major contribution to protein shielding. Neither are Fe-C-N tilt-bend distortions, although a bend at nitrogen is energetically feasible and also gives a large deshielding, as seen with proteins. <21> UI - 1999136955 AU - Yasuhara A AU - Kasano A AU - Sakamoto T IN - A. Yasuhara, Faculty of Pharmaceutical Sciences, Tohoku University, Aobaku, Sendai 980-8578; Japan. E-Mail: yasuhara@mail.pharm.tohoku.ac.jp. TI - Convenient reduction of nitrobenzenes to anilines using electrochemically generated nickel. SO - Journal of Organic Chemistry Vol 64(7) (pp 2301-2303), 1999. AB - The reduction of nitrobenzenes with electrogenerated nickel in DMF gave anilines without affecting the alkenyl, alkynyl, halo, acetyl, methoxy, cyano, ethoxycarbonyl, formyl, benzyloxy, and phenylsulfonylamino groups at room temperature in a short time. The nickel was easily prepared by electrolysis in 0.3 M Et4NBF4-DMF solution under an argon atmosphere at a constant current (10 mA/cm2) and can be stored under argon at -20 [degree] C for at least a week. <22> UI - 1999140126 AU - Boesveld WM AU - Gehrhus B AU - Hitchcock PB AU - Lappert MF AU - Von Rague Schleyer P IN - M.F. Lappert, The Chemistry Laboratory, University of Sussex, Brighton BN1 9QJ; United Kingdom. E-Mail: M.F.Lappert@sussex.ac.uk. TI - A crystalline carbene-silylene adduct 1,2-C6H4[N(R)]2C-Si[N(R)]2C6H4-1,2 (R = CH2Bu(t)); synthesis, structure and bonding in model compounds. SO - Chemical Communications Vol 5(8) (pp 755-756), 1999. AB - The red-brown, crystalline carbene-silylene adduct, 1,2-C6H4[N(R)]2C-Si[N(R)]2C6H4-1,2 (R = CH2Bu(t))4, was obtained from its factors, the carbene 3 and silylene 1, or from Ni{C[N(R)]2(C)6H4-1,2}2 and 1; the X-ray structure of 4 shows a long C-Si bond [2.162(5) [Angstrom] ] and NMR spectral data indicate significant C+-Si- bond polarity, features consistent with DFT calculations at the B3LYP/6-311+G** level on [(CH)2(NH)2]C-Si[(NH)2(CH)2], (H2N)2C-Si(NH2)2 or even [(CH)2(NH)2]C-SiH2 and (H2N)2C-SiH2, but not H2C = Si(NH2)2 or H2C = Si[(NH)2(CH)2]. [References: 16] <23> UI - 1999127067 AU - Pizzocaro C AU - Lessard RA AU - Bolte M IN - M. Bolte, Unite Mixte de Recherche, Ctr. Natl. de la Rech. Scientifique, 6505 Clermont-Ferrand, 63177 Aubiere Cedex; France. E-Mail: boltem@cicsun.univbp-clermont.fr. TI - Charge-transfer phenomena in holographic recording material: Dichromated poly(acrylic acid). SO - Canadian Journal of Chemistry Vol 76(11) (pp 1746-1752), 1998. AB - Dichromated poly(acrylic acid) (DCPAA) has been used as real time holographic recording material. We report here the photochemical behavior of DCPAA when irradiated under conditions representative of those used for hologram recording. Under UV-vis spectroscopy a photoredox process (Cr(VI) [right arrow] Cr(III)) was observed whose efficiency depends on the presence of dimethylformamide (DMF) used as an electron donor. ESR spectroscopy upon irradiation permits detection of the formation of Cr(V) of photochemical origin. We also identified chromium(V) of thermal origin (in the dark), organic macroradicals, and chromium(III). The formation of CO2 and carboxylate ions was clearly shown by IR spectroscopy. The photoreaction is assumed to go through an acido-basic reaction between dichromate in the excited state and poly(acrylic acid). The resulting unstable chromium polyacrylate undergoes a redox process that gives rise to chromium(V) and a macroradical R-COO. from which CO2 is formed. The presence of DMF (10% by volume) makes the overall reaction faster by a factor of approximately 3.5- 4. The similar shape of the curves giving chromium(V) formation as a function of irradiation time and the curves giving the diffraction efficiencies of the hologram recorded in DCPAA as a function of exposure energy, with and without DMF, strongly argues in favor of a direct involvement of chromium(V) in the quality of the resulting hologram. [References: 17] <24> UI - 1999123433 AU - Paquis P AU - Pignol J-P AU - Lonjon M AU - Brassart N AU - Courdi A AU - Chauvel P AU - Grellier P AU - Chatel M IN - P. Paquis, Service de Neurochirurgie, Hopital Pasteur, 30 Avenue de la Voie Romaine, 06002 Nice cedex 1; France. TI - Boron Neutron Capture Enhancement (BNCE) of fast neutron irradiation for glioblastoma: Increase of thermal neutron flux with heavy material collimation, a theoretical evaluation. SO - Journal of Neuro-Oncology Vol 41(1) (pp 21-30), 1999. AB - Despite the fact that fast neutron irradiation of glioblastoma has shown on autopsies an ability to sterilize tumors, no therapeutic windows have been found for these particles due to their toxicity toward normal brain. Therefore, the Boron Neutron Capture Enhancement (BNCE) of fast neutron beam has been suggested. This paper addresses the problem of fast neutron beam collimation, which induces a dramatic decrease of the thermal neutron flux in the depth of the tissues when smaller irradiation fields are used. Thermoluminescent dosimeter TLD-600 and TLD-700 were used to determine the thermal neutron flux within a Plexiglas phantom irradiated under the Nice Biomedical Cyclotron p(60)+Be(32) fast neutron beam. A BNCE of 4.6% in physical dose was determined for a 10 x 10 cm2 field, and of 10.4% for a 20 x 20 cm2 one. A Dose Modification Factor of 1.19 was calculated for CAL 58 glioblastoma cells irradiated thanks to the larger field. In order to increase the thermal flux in depth while shaping the beam, heavy material collimation was studied with Monte Carlo simulations using coupled FLUKA and MCNP-4A codes. The use of 20 cm width lead blocks allowed a 2 fold thermal neutron flux increase in the depth of the phantom, while shielding the fast neutron beam with a fast neutron dose transmission of 23%. Using the DMF of 1.19, a BNCE of 40% was calculated in the beam axis. This enhancement might be sufficient to open, at least theoretically, a therapeutic window. [References: 39] <25> UI - 1999102658 AU - Jarjayes O AU - Hamman S AU - Beguin CG IN - C.G. Beguin, Universite J. Fourier, UFR de Chimie, LEDSS, BP. 53X, 38051 Grenoble Cedex 09; France. TI - Use of 19F NMR for studies of the complexation of gallium (III) by 5- fluoro-8-hydroxyquinoline. SO - J CHIM PHYS PHYS-CHIM BIOL, Vol 95(2) (pp 395-400), 1998. AB - Stereochemical and structural informations have been obtained by 1D and 2D 19F NMR spectroscopy of solutions containing a diamagnetic cation Ga(III) and a fluorinated ligand named 5-fluoro-8-hydroxyquinoline (Fox). In organic medium (DMF-d7), and at low temperature, Ga(Fox)3 has been studied in details using homo- and heteronuclear correlations. [References: 6] <26> UI - 1999096120 AU - Rodebaugh R AU - Debenham JS AU - Fraser-Reid B AU - Snyder JP IN - B. Fraser-Reid, Paul M. Gross Chemical Laboratory, Duke University, Durham, NC 27708; United States. TI - Bromination of alkenyl glycosides with copper(II) bromide and lithium bromide: Synthesis, mechanism, and DFT calculations. SO - Journal of Organic Chemistry Vol 64(5) (pp 1758-1761), 1999. <27> UI - 1999076959 AU - Saebo S AU - Stroble S AU - Collier W AU - Ethridge R AU - Wilson Z AU - Tahai M AU - Pittman CU Jr IN - S. Saebo, Department of Chemistry, Mississippi State University, Mississippi State, MS 39762; United States. TI - Aromatic character of tria- and pentafulvene and their exocyclic Si, Ge, and Sn derivatives. An ab initio study. SO - Journal of Organic Chemistry Vol 64(4) (pp 1311-1318), 1999. AB - The structures and dipole moments have been calculated for both methylenecyclopropene (triafulvene) and pentafulvene and their exocyclic Si, Ge, and Sn analogues 1a-d and 2a-d, respectively. Ab initio calculations employing the HF, DFT, and MP2 methods, each using split valence plus polarization and triple split valence with two sets of polarization functions basis sets, have been performed. The results of these six levels of theory on each of the eight molecules were compared, and the aromatic character of these systems was examined. The structures 1a-d exhibited pronounced bond alternation in the ring suggesting the existence of only weak cyclopropenyl cation-like resonance contribution. However, very large dipole moments were predicted in the direction that would be expected from an aromaticity contribution. Since Si, Ge, and Sn are less electronegative than C, the large dipole moments in the direction of the exocyclic heteroatom were surprising. The most striking finding was that, while la is planar, 4-sila-, 4-germa-, and 4-stannatriafulvene were nonplanar with trans-bent structures in which the exocyclic double bond is bent slightly out of the cyclopropene ring plane and out of the HXH plane (X = Si, Ge, Sn) by large angles. Thus, the Si, Ge, and Sn atoms exhibit pyramidal geometries. The dipole moment of pentafulvene, 2a, (oriented toward the ring) was substantially smaller than that of its Si, Ge, and Sn analogues, 2b-d. The large dipoles of 2b-d were due to greater charge separation resulting from the lower electronegativities of Si, Ge, and Sn versus that of C. The cyclopentadienyl rings exhibited strong bond alternation indicating only a modest cyclopentadienyl anion-like contribution in 2b-d. <28> UI - 1999068991 AU - Zhou P AU - Au-Yeung SCF AU - Xu X-P IN - S.C.F. Au-Yeung, Department of Chemistry, Chinese University of Hong Kong, Shatin, New Territories; Hong Kong. TI - A DFT and 59Co solid-state NMR study of the second-sphere interaction in polyammonium macrocycles cobalt cyanide supercomplexes. SO - Journal of the American Chemical Society Vol 121(5) (pp 1030-1036), 1999. AB - The second-sphere interaction for a series of supercomplexes formed from the binding of [Co(CN)6]3-, a photochemical active metal complex, with preorganized protonated polyammonium macrocyclics has been studied with 59Co solid-state NMR and ab initio quantum chemical methods at the DFT level. For the supercomplexed studied in this work, the 59Co NMR chemical shift of [Co(CN)6]3- has been successfully computed, demonstrating that the hybrid XC functional method is equally in rationalizing small adjustments in structural and electronic modification at the metal center. This success has confirmed that the entire 59Co chemical shift range may be predicted with reasonable confidence. The charge-transfer mechanism has also been established on the basis of the correlations between the 59Co chemical shifts and the relative contribution of cobalt-3d orbitals to second-order interaction energies, as well as structure parameters. The shielding tensor results confirmed that the structure distortions occurring in these supercomplexes are the direct consequence of the second-sphere interaction resulting from site-symmetry being lowered at cobalt. Thus, the degeneracy of the electron energy state (1T(1g)) at cobalt has been lifted, resulting in splitting of the energy levels. <29> UI - 1999042073 AU - Tian F AU - Bartberger MD AU - Dolbier WR Jr IN - W.R. Dolbier Jr., Department of Chemistry, University of Florida, Gainesville, FL 32611-7200; United States. TI - Density functional theory calculations of the effect of fluorine substitution on the kinetics of cyclopropylcarbinyl radical ring openings. SO - Journal of Organic Chemistry Vol 64(2) (pp 540-546), 1999. AB - DFT calculations (B3LYP/6-311+G(2df,2p)//B3LYP/6-31G(d)) indicate a dramatic impact of fluorine substituents on the structure and reactivity of the cyclopropylcarbinyl radical. Stereoelectronic influences are believed to be largely responsible for the predicted reactivity and regiospecificity of fluorinated radicals such as the 2,2-difluorocyclopropyl carbinyl radical, which has a calculated activation barrier of 1.9 kcal/mol, undergoing regiospecific C2-C3 cleavage to form the 2,2-difluoro homoallylic radical. In contrast, calculations indicate that the 2,2-difluorocyclopropylcarbinyl cation will convert regiospecifically to the 1,1-difluoro homoallylic cation. <30> UI - 1999020157 AU - Kemper PR AU - Weis P AU - Bowers MT AU - Maitre P IN - M.T. Bowers, Department of Chemistry, University of California, Santa Barbara, CA 93106-9510; United States. TI - Origin of bonding interactions in Cu+(H2)(n) clusters: An experimental and theoretical investigation. SO - Journal of the American Chemical Society Vol 120(51) (pp 13494-13502), 1998. AB - Binding energies and entropies have been measured for the attachment of up to six H2 ligands to ground-state Cu+ ions (1S, Ar3d10), to electronically excited Cu+*ions (1,3D, Ar4s(I)3d9), and to hydrated H2O. Cu+ ions. The ground-state Cu+ ion added four H2 ligands in the first solvation shell with bond dissociation energies (BDEs) of 15.4, 16.7, 8.8, and 5.1 kcal/mol. The fifth and sixth ligands begin a new solvation sphere and were very weakly bound. The BDEs for addition of H2 to electronically excited Cu+*were also small (4.2, 2.5, and 1.4 kcal/mol for the first three ligands). The difference between ground- and excited-state association energies is almost entirely due to the repulsive nature of the 4s electron. Hydration of the Cu+ ion significantly increased the BDE of the first H2 ligand (to 19.6 kcal/mol) but greatly reduced that of the second (to 3.8 kcal/mol). Theoretical calculations with large basis sets at the DFT- B3LYP and MP2 levels were done on all species both to determine geometries and vibration frequencies and to examine the origin of the bonding and its variation with Cu+ coordination. The calculations show that covalent interactions are important in these Cu+ clusters and that the observed changes in BDE as different ligands are added are due to electronic rather than steric effects. These sources of bonding are discussed, and comparisons are made to the Co+(H2)(n) and Ni+(H2)(n) systems. It is also shown that the M+-ligand interactions are similar for H2 and CO ligands. Special attention is paid to the origin of the highly symmetric D(3h) planar structure found in Ni+(H2)3, Cu+(H2)3, and Cu+(CO)3. <31> UI - 1999006441 AU - Duan J AU - Dolbier WR Jr AU - Chen Q-Y IN - W.R. Dolbier Jr., Department of Chemistry, University of Florida, Gainesville, FL 32611-7200; United States. TI - A new and improved synthesis of trans-1,2-diiodoalkenes and their stereospecific and highly regioselective trifluoromethylation. SO - Journal of Organic Chemistry Vol 63(25) (pp 9486-9489), 1998. AB - Reaction of terminal alkynes with iodine in the presence of CuI (5%) in acetonitrile under reflux for several hours gave the trans-1,2-diiodoalkenes in high yields. The trifluoromethylation of these diiodides using FSO2CF2CO2Me/CuI/DMF proceeded in excellent yields in a stereospecific and highly regioselective manner. <32> UI - 1998395513 AU - Zhou M AU - Andrews L IN - L. Andrews, Department of Chemistry, University of Virginia, Charlottesville, VA 22901; United States. TI - Matrix infrared spectra and density functional calculations of Ni(CO)(x)/-, x = 1-3. SO - Journal of the American Chemical Society Vol 120(44) (pp 11499-11503), 1998. AB - Laser-ablated Ni atoms and electrons react with CO in excess argon during condensation to form the Ni(CO)1-4 complexes and N1(CO)1-3- anions. Matrix infrared spectra of the neutral complexes with 12C16O, 13C16O, and 12C18O substitution are in agreement with earlier reports with thermal Ni atoms. In addition, new absorptions at 1847.0, 1801.7, and 1858.8 cm-1 exhibit isotopic spectra in excellent agreement with DFT calculations for the Ni(CO)1-3- anions. An experiment doped with the CCl4 electron-trapping molecule gave the same Ni(CO)1-4 spectrum without the corresponding anions, which strongly supports this identification of the molecular anions. <33> UI - 1998370929 AU - Hanson AA AU - Rogan EG AU - Cavalieri EL IN - E.L. Cavalieri, Eppley Inst. for Research in Cancer, Dept. of Pharmaceutical Sciences, Univ. of Nebraska Medical Center, Omaha, NE 68198-6805; United States. E-Mail: ecavalie@mail.unmc.edu. TI - Synthesis of adducts formed by iodine oxidation of aromatic hydrocarbons in the presence of deoxyribonucleosides and nucleobases. SO - Chemical Research in Toxicology Vol 11(10) (pp 1201-1208), 1998. AB - Polycyclic aromatic hydrocarbons (PAH) undergo two main pathways of metabolic activation related to the initiation of tumors: one-electron oxidation to give radical cations and monooxygenation to yield bay-region diol epoxides. Synthesis of standard adducts is essential for identifying biologically formed adducts. Until recently, radical cation adducts were synthesized by oxidation of the PAH in an electrochemical apparatus, not readily available in many organic chemistry laboratories. We have developed a convenient and efficient method for synthesizing PAH-nucleoside adducts by using I2 as the oxidant. Adducts of benzo[a]pyrene (BP), dibenzo[a,l]pyrene (DB[a,l]P), and 7,12-dimethylbenz[a]anthracene were synthesized with deoxyguanosine (dG), deoxyadenosine, guanine (Gua), or adenine in either Me2SO or dimethylformamide (DMF) with or without AgC104. When, for example, the potent carcinogen BP was dissolved in DMF in the presence of 3 equiv of I2, 5 equiv of dG, and 1 equiv of AgC104, 45% of the BP was converted to BP-6-N7Gua. When BP was placed under the same reaction conditions in the absence of AgC104, the extent of formation of BP-6-N7Gua decreased to 30%. When the potent carcinogen DB[a,l]P was dissolved in DMF in the presence of 3 equiv of I2, 5 equiv of dG, and 1 equiv of AgC104, 43% of the DB[a,l]P was converted to DB[a,l]P-10-N7Gua. In the more polar solvent Me2SO under the same reaction conditions, however, the yield of DB[a,l]P-10-N7Gua was only 20%. Synthesis of adducts with the oxidant I2 is more convenient and, in some cases, more efficient than synthesis by electrochemical oxidation. This method simplifies the synthesis of PAH-nucleoside and nucleobase adduces that are essential for studying biologically formed PAH-DNA adducts. [References: 24] <34> UI - 1998287761 AU - Bernardi F AU - Bottoni A AU - Rossi I IN - F. Bernardi, Dipto. di Chimica 'G. Ciamician', Universita' di Bologna, via Selmi 2, 40126 Bologna; Italy. TI - A DFT investigation of ethylene dimerization catalyzed by Ni(0) complexes. SO - Journal of the American Chemical Society Vol 120(31) (pp 7770-7775), 1998. AB - In this paper we have studied the [2+2] cycloaddition of two olefins catalyzed by Ni(0) complexes using a hybrid DFT/B3LYP computational approach with the pseudopotential LANL2DZ basis set. Two model systems have been used to emulate the catalytic process: the ethylene-nickel complex Ni(PH3)2C2H4 and the bis(ethylene)-nickel complex Ni(PH3)2(C2H4)2, both reacting with an ethylene molecule. For both these complexes we have investigated in detail the first steps of the catalytic process, corresponding to the formation of nickelacyclopentane, which has been experimentally demonstrated to produce the cyclobutane product by reductive elimination. We have found that the incoming ethylene molecule reacts with both complexes not at the metal center but at one ligand ethylene. This attack affords an anti 1,5-biradical intermediate that can lead to nickelacyclopentane and where the two unpaired electrons are mainly localized on the nickel atom and on the terminal methylene. While for the attack of the ethylene molecule on Ni(PH3)2C2H4 no catalytic effect is observed (the activation energy is almost identical to that found for the noncatalyzed process, i.e., about 40 kcal mol-1), a catalytic effect, even if not very large, is found for the Ni(PH3)2(C2H4)2 complex (the barrier decreases to 35.80 kcal mol-1). Adiabatic analysis has pointed out that the factors which are responsible for the catalytic effect of the Ni(PH3)2(C2H4)2 complex are the energy gap between the singlet ground state and the first triplet state in the complex and the stability of the biradical intermediate. <35> UI - 1998281427 AU - Lee T-W AU - Chang S-R AU - Chen S-T AU - Tsai Z-T IN - T.-W. Lee, Institute of Nuclear Energy Research, Lung-Tan; Taiwan. TI - Convenient solid-phase synthesis of Tyr3-octreotide. SO - Applied Radiation & Isotopes Vol 49(12) (pp 1581-1586), 1998. AB - We have developed a new method to anchor Thr(ol) to a solid-phase synthesis resin for preparation of Tyr3-octreotide. Fmoc-Thr(ol)-terephthal- acetal, prepared from Fmoc-Thr-OH, was loaded onto the resin. After construction of the peptide chains by Fmoc chemistry, cyclization of the peptide may be obtained on-resin by oxidation with iodine in DMF. The cleavage of the peptide-resin with trifluoroacetic acid, followed by the reverse-phase HPLC purification, produced Tyr3-octreotide with an overall yield of 40% from the starting Fmoc-Thr(ol)-terephthal-acetal-resin. The final product gave a single peak on analytical HPLC and electrospray mass spectrometry confirmed the integrity of the product. Iodine-123 radiolabeling of the product provided 123I-Tyr3-octreotide with > 98% radiochemical purity. [References: 5] <36> UI - 1998274122 AU - Hodgson DM AU - Foley AM AU - Lovell PJ IN - D.M. Hodgson, Dyson Perrins Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QY; United Kingdom. TI - Improved Cr(II)-mediated synthesis of E-alkenylstannanes from aldehydes using Bu3SnCHI2 in DMF. SO - Tetrahedron Letters Vol 39(35) (pp 6419-6420), 1998. AB - An improved chromium(II)-mediated synthesis of E-alkenylstannanes from aldehydes using Bu3SnCHI2 in DMF is described. [References: 8] <37> UI - 1998240017 AU - Stoor P AU - Soderling E AU - Salonen JI IN - P. Stoor, Institute of Dentistry, University of Turku, Turku Centre for Biomaterials, Turku; Finland. TI - Antibacterial effects of a bioactive glass paste on oral microorganisms. SO - Acta Odontologica Scandinavica Vol 56(3) (pp 161-165), 1998. AB - Bioactive glasses contain oxides of calcium, sodium, phosphorus, and silicon in a proportion that provides the material with surface activity and concomitantly with the property of forming a strong bond with bone. Bioactive glasses have been tested as bone substitutes in different clinical situations. In an aqueous environment, Ca2+, Na+, PO43-, and Si4+ are released from the glass, resulting in a rise in pH and in osmotic pressure in its vicinity. Since these are factors that potentially influence the viability of oral microorganisms at the dentogingival margin, we studied the effects of bioactive glass S53P4 on the oral microorganisms Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Actinomyces naeslundii, Streptococcus mutans, and Streptococcus sanguis. This was done by incubating each microbe in a suspension, in the presence of bioactive glass S53P4 in powder form. A. naeslundii was found to lose its viability within 10 min under the experimental conditions. A. actinomycelemcomitans, P. gingivalis, and S. mutans lost their viability within 60 min. Also for S. sanguis a significant loss of viability was seen within 60 min, but it was the only microbe that had any viable cells left after 60 min. Thus, in aqueous solutions the powdered bioactive glass S53P4 appears to have abroad antimicrobial effect on microorganisms of both supra- and subgingival plaque. Consequently, it could be useful as an ingredient in tooth-care products that may have beneficial effects on oral health both from a cariologic and a periodontal point of view. [References: 23] <38> UI - 1998234814 AU - Beletskaya IP AU - Davydov DV AU - Moreno-Manas M IN - I.P. Beletskaya, Chemical Dept. of Moscow State Univ., Leninsky Gory, Moscow 119899, GSP-3; Russian Federation. TI - Pd- and Cu-catalyzed selective arylation of benzotriazole. SO - Tetrahedron Letters Vol 39(31) (pp 5617-5620), 1998. AB - Palladium(0)-catalyzed arylation of 1H-1,2,3-benzotriazole (BTA) in DMF at 150 [degree] C in the presence of copper salt with arylhalides proceeds regioselectively at N-1 position. Best result has been obtained with the PdCl2(dppe) as catalyst and the Cu(II) phenylcyclopropylcarboxylate as co- catalyst. [References: 9] <39> UI - 1998221811 AU - Coppell D IN - D. Coppell, Fusion Associates UK Limited, 23 Woodland Ave, Windsor, Berks. SL4 4AG; United Kingdom. TI - The significance of water chemistry in wet plant operation. SO - Radiation Physics & Chemistry Vol 52(1-6) (pp 413-417), 1998. AB - The use of cobalt radiation sources in a wet storage environment requires care in the control of that environment to avoid the potential for deterioration of the steel. This paper describes the factors which are important and recommends a set of water quality conditions. It also describes the measures which PURIDEC has taken to monitor the performance of product in service and outlines some of the results from that surveillance programme. [References: 2] <40> UI - 1998214049 AU - Kovala-Demertzi D AU - Hadjikakou SK AU - Demertzis MA AU - Deligiannakis Y IN - D. Kovala-Demertzi, Inorganic and Analytical Chemistry, Department of Chemistry, University of Ioannina, 45110 Ioannina; Greece. E-Mail: dkovala@cc.uoi.gr. TI - Metal ion-drug interactions. Preparation and properties of manganese (II), cobalt (II) and nickel (II) complexes of diclofenac with potentially interesting anti-inflammatory activity: Behavior in the oxidation of 3,5-di- tert-butyl-o-catechol. SO - Journal of Inorganic Biochemistry Vol 69(4) (pp 223-229), 1998. AB - Some new complexes of diclofenac with potentially interesting biological activity are described. The complexes of diclofenac [MnL2(H2O)], [CoL2(H2O)2].0.5H2O, [CoL2(H2O)], [NiL2(H2O)2].2H2O, and [NiL2], were prepared by the reaction of the sodium salt, of a potent anti- inflammatory drug with MnCl2, CoCl2 and NiCl2.6H2O. Optical, EPR, infrared and electrochemical properties of these new complexes are reported. Both five and six-coordinated species were isolated in the solid state for Co(II). Both four and six-coordinated species were isolated in the solid state for Ni(II), while in DMF or MeOH solution predominant formation of six- coordinated species is observed for Co(II) and Ni(II) complexes. The ability of the complexes to catalyze the oxidation of 3,5-di-tert-butyl-o-catechol to 3,5-di-tert-butyl-o-quinone was studied by following the appearance of quinone spectrophotometrically. Correlation of the catalytic activity of these complexes to the reduction potential is reported. [References: 9] <41> UI - 1998209733 AU - Cotton FA AU - Feng X IN - F.A. Cotton, Department of Chemistry, Lab. for Molecular Structure/Bonding, Texas A and M University, College Station, TX 77843-3255; United States. TI - Density functional theory study of transition-metal compounds containing metal-metal bonds. 2. Molecular structures and vibrational spectra of dinuclear tetracarboxylate compounds of molybdenum and rhodium. SO - Journal of the American Chemical Society Vol 120(14) (pp 3387-3397), 1998. AB - Vibrational spectra have been calculated for the first time for dinuclear transition-metal compounds containing metal-metal bonds. The calculations were carried out by employing different forms of density functional theory (DFT) and basis functions of different sizes at fully optimized molecular geometry. The calculated frequencies essentially reproduced fundamentals observed in experimental infrared and Raman spectra. It is shown that DFT frequency calculations can be a very important and valuable tool to assist in analyzing and assigning measured infrared and Raman spectra and to predict vibrational frequencies for large transition- metal compounds with metal-metal bonds. The molecules included in this study were M2(O2CH)4 (M = Mo, Rh), Rh2(O2CH)4(H2O)2, and M2(O2CCH3)4 (M = Mo, Rh). Significant differences are found between the formate and acetate molecules. <42> UI - 1998157723 AU - McGuire MA AU - Sorenson E AU - Klein DN AU - Baine NH IN - M.A. McGuire, SmithKline Beecham Pharmaceuticals, Synthetic Chemistry Department, P.O. Box 1539, King of Prussia, PA 19406; United States. TI - Palladium and nickel catalyzed hydroxycarbonylation of a steroidal bromodiene in the synthesis of episteride, a potent 5alpha-reductase inhibitor. SO - Synthetic Communications Vol 28(9) (pp 1611-1615), 1998. AB - Androst-4-en-3-one-17beta-carboxylic acid 1 was converted to 3-bromo-N- (l,1-dimethylethyl) androsta-3,5-diene-17-beta-carboxamide 2 by reaction with DMF/oxalyl bromide and quenching into t-butylamine. 2 was converted to 3 (R=H) by nickel cyanide catalyzed hydroxycarbonylation or palladium (0) catalyzed hydroxycarbonylation. [References: 13] <43> UI - 1998148600 AU - Jones GS AU - Mavrikakis M AU - Barteau MA AU - Vohs JM IN - M.A. Barteau, Ctr. for Catalytic Sci. and Technol., Department of Chemical Engineering, University of Delaware, Newark, DE 19716; United States. TI - First synthesis, experimental and theoretical vibrational spectra of an oxametallacycle on a metal surface. SO - Journal of the American Chemical Society Vol 120(13) (pp 3196-3204), 1998. AB - High-resolution electron energy loss spectroscopy (HREELS) studies were performed to examine the reactions of 2-iodoethanol (ICH2CH2OH) on the Ag(110) surface. The goal of these experiments was to isolate and spectroscopically characterize a stable surface oxametallacycle, an intermediate previously proposed but never isolated in the chemistry of a variety of oxygenates, including epoxides. The hydroxyethyl intermediate (- CH2CH2OH), formed from initial carbon-iodine bond scission, decomposed at 263 K to yield a variety of volatile products as well as a surface oxametallacycle (-CH2CH2O-). The oxametallacycle intermediate, formed at 263 K, remained intact until 340 K, permitting spectroscopic characterization by HREELS. Density Functional Theory (DFT) calculations were employed to determine the fully optimized structure for the oxametallacycle on silver and to predict the infrared spectrum and molecular motions for that structure. The excellent agreement between the infrared spectrum predicted for an oxametallacycle incorporating two silver atoms and the experimental HREEL spectrum conclusively identifies the surface oxametallacycle. The principal reaction channel for this intermediate in temperature programmed desorption (TPD) experiments is coupling of two oxametallacycles to form the cyclic product gamma-butyrolactone, rather than the anticipated ring closure: pathway to form ethylene oxide. However, one of the vibrational modes predicted by DFT appears to be a possible reaction coordinate for the conversion of oxametallacycles to ethylene oxide. <44> UI - 1998140060 AU - Poli R AU - Wang L-S IN - R. Poli, Lab. Synthese/Elec.synthese Org.met, Faculte des Sciences 'Gabriel', 6, Boulevard Gabriel, 21100 Dijon; France. E-Mail: Rinaldo.Poli@u-bourgogne.fr. TI - Cyclopentadienylmolybdenum(II) and -(III) complexes containing diene and allyl ligands. 2. Comparative reactivity of the isomeric complexes cpMo(eta- C3H5)(eta-C4H6) with either supine or prone allyl and either s-cis (supine) or s-trans Butadiene ligands toward protons. SO - Journal of the American Chemical Society Vol 120(12) (pp 2831-2842), 1998. AB - The electron-rich isomeric complexes CpMo(eta3-C3H5)(eta4-C4H6) (la, prone-C3H5; supine-C4H6; lb, supine-C3H5; supine-C4H6; lc, supine- C3H5; s-trans-C4H6) do not react with neutral ligands under mild conditions. They are, however, easily protonated by a variety of different acids. Protonation of la and lb involves attack at the terminal position of the allyl ligand and elimination of propene. Protonations with acetic acid show rates in the order la > lb and afford the same product, CpMo(O2CCH3)(eta4-C4H6), 2, which can be oxidized to the 17-electron cation [2]+. HBF4 protonation of la in the absence of trapping donor molecules affords [CpMo(eta4-supine-C4H6)(mu-F2BF2)](n), 3. The latter readily reacts with donor molecules to afford [CpMo(eta4-supine- C4H6)L2][BF4] products (L = MeCN, 4; Bu(t)NC, 5; or L2 = 1,3-butadiene, 6), which are also directly and selectively obtained by protonation of 1a in the presence of the appropriate ligand. Compound 6 has a (supine-C4H6)(s- trans-C4H6) configuration and converts into compound 4 when dissolved in MeCN. Protonation of lc is much slower relative to the isomers la and lb. The observed products depend on the nature of the solvent. Protonation by HBF4*Et2O in MeCN affords unstable [CpMo(supine-eta-C3H5)(syn-CH3- prone-eta-C3H4)(NCCH3)][BF4] (7), which rapidly exchanges the MeCN ligand. Decomposition of the latter involves a regioselective reductive coupling of the two allyl ligands to generate 3-methyl-l,5-hexadiene quantitatively. In C6D6, the HBF4 protonation of lc produces small amounts of propene and a violet precipitate which gives a mixture of 4 and 7 upon treatment in MeCN. In the presence of 1,3-butadiene, protonation of lc in THF followed by extraction into acetone affords a mixture of 6 and [CpMo(eta-C3H4-CH2CH2- eta-C3H4)(Me2CO)][BF4] (8). Compound 8 converts into [CpMo(eta-C3H4- CH2CH2-eta-C3H4)(L)][BF4] (L = MeCN, 9; PMe3, 10) when treated with the appropriate L. Protonation of 1c in MeCN in the presence of butadiene affords 7 which slowly decomposes, under these conditions, to a mixture of 4 and [CpMo(eta4-s-trans-C4H6)(MeCN)2]+, 11. The collective results for the protonation of 1c indicate that the proton attacks the s-trans diene ligand in MeCN. The preferred position of attack in nonpolar solvents, on the other hand, is the allyl. The difference of electronic distribution for isomers 1a- c has been investigated by DFT methods. The calculations indicate that the allyl ligand is a stronger donor in the supine configuration, while the diene ligand is both a weaker donor and a weaker acceptor when it is coordinated in the s-trans mode. <45> UI - 1998101453 AU - Ghaneolhosseini H AU - Tjarks W AU - Sjoberg S IN - H. Ghaneolhosseini, Department of Organic Chemistry, Uppsala University, Box 531, S-75121 Uppsala; Sweden. TI - Synthesis of novel boronated acridines- and spermidines as possible agents for BNCT. SO - Tetrahedron Vol 54(15) (pp 3877-3884), 1998. AB - An approach to synthesise three different boronated DNA-interacting compounds (11, 15 and 19) is described. Compound 11 is containing both an acridine system and a spermidine residue. The acridine moiety would serve as DNA intercalating fragment whereas the spermidine residue functions both as water-solubilising and DNA-interacting part. 1,12-p-Carboranyl bis[N-3- aminopopyl, N-4-aminobutyl)-3-propane amide] hydrogen chloride (15) was obtained by treating 13 first with ethyl chloroformate and then the secondary amine 2. Finally, 1,12-Bis(N-(9-acridinyl)3-aminopropyl)-p-carborane hydrogen chloride (19) was accomplished by hydrochloronation of the corresponding free amine which was obtained by the treatment of 18 with 9 in toluene/DMF. [References: 19] <46> UI - 1998046668 AU - Pavlov M AU - Siegbahn PEM AU - Blomberg MRA AU - Crabtree RH IN - M. Pavlov, Department of Physics, Stockholm University, S-113 85 Stockholm; Sweden. TI - Mechanism of H-H activation by nickel-iron hydrogenase. SO - Journal of the American Chemical Society Vol 120(3) (pp 548-555), 1998. AB - DFT quantum chemical methods are used to probe the mechanism of the nickel-iron hydrogenases. Starting from the experimental X-ray structure, all plausible oxidation states and spin states were investigated. The structure and reactivity pattern of the NiFe cluster are best-reproduced by assuming a NiFe(II,III) oxidation state assignment of the resting state of the cluster. In our proposed mechanism of H2 oxidation by the enzyme, H2 first binds to Fe in the form of a molecular hydrogen complex, which then undergoes heterolytic splitting. This process is spin-dependent and does not occur for the high-spin sextet state. In the key step, hydride transfer to iron and proton transfer to the adjacent cysteinehiolate ligand is accompanied by decoordination of the protonated cysteinethiol from Ni while remaining bound to iron. Simultaneously, the cyanide ligand on iron binds with the nickel atom in a rare bridging binding mode filter the H2 dissociation, the hydride bound to Fe can then be transferred to Ni which should be a necessary preliminary for subsequent hydrogen atom or electron transport. The transition state for hydrogen splitting was located, and the resulting calculated energy barrier is in remarkably good agreement with the experimental value. [References: 37] <47> UI - 1997384302 AU - Nair KM AU - Sesikeran B AU - Ranganathan S AU - Sivakumar B IN - Dr. B. Sivakumar, National Institute of Nutrition, ICMR, Jamai-Osmania PO, Hyderabad-500 007; India. E-Mail: icmrnin@ren.nic.in. TI - Bioeffect and safety of long-term feeding of common salt fortified with iron and iodine (double fortified salt) in rat. SO - Nutrition Research Vol 18(1) (pp 121-129), 1997. AB - A doubly fortified salt formulation developed at NIN as a public health measure for combating iron deficiency anemia and iodine deficiency disorders was evaluated for its efficacy and safety in experimental rats. The hemoglobin regenerating ability of diet with double fortified salt (DFS) containing 1000 ppm iron, 30 ppm iodine and 1% of sodium hexametaphosphate (SHMP), as the stabilizer, was compared to that of diets with iron fortified salt (IFS 1000 ppm) and unfortified salt in rat model using a depletion- repletion method. The safety and long-term feeding of DFS in relation to calcium and phosphorus metabolism was also tested. The results revealed that the amounts of hemoglobin regenerated in both the supplemented salt fed groups (DFS: 13.0 +/- 1.4 and IFS: 11.7 +/- 1.4 g/dl) were significantly higher than that in the unsupplemented group (7.6 +/- 4.0 g/dl) at the end of 4 weeks. Though an increase in the excretion of iodine was seen in DFS fed group (5.2 +/- 5.2 mug I/day) compared to IFS fed group (1.3 +/- 0.45 mug I/day) at the end of 9 months, it was not statistically significant and also both the groups had comparable hemoglobin levels (15 g/dl) and liver iron content (73 mug iron/g liver). Serum alkaline phosphatase (164 +/- 6.7 vs 132 +/- 25.2 IU/L) and calcium (10.1 +/- 0.6 vs 10.2 +/- 0.9 mg/dl) and urinary phosphate (12.1 +/- 4.2 vs 11.4 +/- 2.5 mg/day), calcium (5.4 +/- 3.2 vs 5.1 +/- 1.9 mg/day) and creatinine (9.3 +/- 2.3 vs 8.3 +/- 1.5 mg/day) were found to be similar in DFS and IFS groups, at the end of 9 months of feeding the respective diets. However, there was a significant increase in serum phosphate (11.4 +/- 0.7 vs 7.2 +/- 0.7 mg/dl P<0.01) in the DFS fed group as compared to the IFS fed controls. Whole body x-ray of the DFS and control groups suggested no gross bone abnormality. Histopathological examination of major organs did not indicate any differences between the two groups. Thus, the study revealed that the iron provided through DFS is bioavailable. SHMP per se had no effect on calcium and phosphorus metabolism, except for an increase in serum phosphorus, the significance of which is not known. However, all the other indicators tested showed no evidence of any toxicity due to the long term consumption of DFS. [References: 23] <48> UI - 97333334 AU - Zhang J-L AU - Chen Z-C IN - Z.-C. Chen, Department of Chemistry, Hangzhou University, Hangzhou, 310028; China. TI - Hypervalent iodine in synthesis XXVI: A convenient synthesis of acetylenic tellurides. SO - Synthetic Communications Vol 27(22) (pp 3881-3885), 1997. AB - Acetylenic tellurides have been prepared by the reaction of sodium arenetellurolates with alkynylphenyliodonium tosylates in DMF. [References: 8] <49> UI - 97245626 AU - Yamazaki K AU - Kawai Y AU - Inoue N AU - Shinano H IN - Dr. K. Yamazaki, Laboratory of Food Wholesomeness, Faculty of Fisheries, Hokkaido University, 3-1-1, Minato, Hakodate, Hokkaido 041; Japan. E-Mail: yamasaki@pop.fish.hokudai.ac.jp. TI - Influence of sporulation medium and divalent ions on the heat resistance of Alicyclobacillus acidoterrestris spores. SO - Letters in Applied Microbiology Vol 25(2) (pp 153-156), 1997. AB - The influence of divalent cations on the heat resistance of spores of the thermoacidophilic spoilage bacterium Alicyclobacillus acidoterrestris was studied. The heat resistance of A. acidoterrestris spores was not affected by the presence of the different divalent cations (Ca2+, Mg2+, Ba2+, Mn2+ and Sr2+) in the sporulation medium, and by the demineralization or remineralization. And the Ca and Mn contents in A. acidoterrestris spores were scarcely changed by these treatments. However, the heat resistance of Bacillus subtilis spores was affected with the changes of Ca content in the spores. The Ca contents in A. acidoterrestris spores of the different forms were greater than the DPA content. In contrast, the DPA content in the B. subtilis spores was greater than the Ca content. These findings suggest that the presence of constant amount of Ca-DPA and a stronger binding characteristic of divalent ions, especially Ca and Mn, is reflected in the specific heat resistance of A. acidoterrestris spores. [References: 14] <50> UI - 97189015 AU - Ma DS AU - Paik DI AU - Park DY AU - Moon HS AU - Chang YI AU - Kim JB IN - D.S. Ma, College of Dentistry, Seoul National University, 28 Yeongeon-dong, Chongro-gu, Seoul 110-749; South Korea. TI - Relationship between microhardness and fluorine contents on tooth enamel determined by PIGE analysis. SO - Journal of Radioanalytical & Nuclear Chemistry Vol 217(2) (pp 225-227), 1997. AB - The remineralization effect of fluoride has been measured by surface microhardness on tooth enamel. The purpose of this study was to investigate the relationship between microhardness and fluorine concentration on tooth enamel. Twelve sound bovine enamel specimens were prepared and immersed in 0.05% NaF solution for 1, 3, 6, 24 and 36 hours, respectively. The concentration of fluorine in specimens were measured by PIGE analysis and surface microhardness of each specimen was measured by surface microhardness tester. Fluorine concentration was increased by immersing time. There was no change in microhardness of each specimen by fluorine content. The results of this study suggest that there was no relationship between the fluorine concentration and surface microhardness in sound tooth enamel. PIGE analysis can be used effectively to assess the remineralization effect of fluorine content in tooth enamel. [References: 11] <51> UI - 97189014 AU - Paik DI AU - Ma DS AU - Park DY AU - Moon HS AU - Chang YI AU - Kim JB IN - D.I. Paik, College of Dentistry, Seoul National University, 28, Yeongeon-dong, Chongro-ku, Seoul 110-749; South Korea. TI - Determination of fluorine by PIGE analysis on bovine tooth enamel treated with bamboo salt SMFP toothpaste and fluoride mouth rinsing solution. SO - Journal of Radioanalytical & Nuclear Chemistry Vol 217(2) (pp 221-223), 1997. AB - The purpose of this study was to evaluate the effectiveness of a toothpaste containing bamboo salt on fluorine uptake in bovine enamel and to compare the efficiency of fluorine uptake between sodium monofluorophosphate (SMFP) toothpaste and sodium fluoride (NaF) mouthrinsing solution using proton induced gamma-ray emission analysis. 30 bovine tooth enamel specimens were prepared and assigned to 5 groups as follows: (a) specimens without any treatment, (b) specimens which were treated with a toothpaste containing dicalcium phosphate dihydrate (DCPD) only, (c) specimens which were treated with a toothpaste containing DCPD and SMFP, (d) specimens which were treated with a toothpaste containing DCPD, SMFP and 2% bamboo salt, (e) specimens which were treated with 0.05% NaF mouthrinsing solution. After 5 and 10 hours of treatment, fluorine concentration was measured at the depth of 263, 625, 2530 nm from the surface of the specimens. The surface concentration of fluorine was markedly increased using SMFP dentifrice. Bamboo salt did not encourage the uptake of fluorine into the enamel surface. NaF mouthrinsing solution showed a considerably higher uptake of fluoride in the intact enamel surface than the SMFP dentifrices. [References: 9] <52> UI - 97151469 AU - Waldron KA AU - Topich J TI - Electrochemical and spectroscopic studies of a molybdenum cofactor model in aqueous micellar solution. SO - Journal of Inorganic Biochemistry Vol 66(4) (pp 267-271), 1997. AB - A model of the molybdenum cofactor (Mo-co) of the molybdenum hydroxylases is examined in a variety of solvent environments that enhance the enzyme-mimetic properties of the complex. The complex MoO2(1L), 1, where 1L = N,N'-dimethyl-(N,N'-bis(2-mercaptophenyl)-1, 2-diaminoethane), has been studied by cyclic voltammetry and infrared spectroscopy in DMF and in aqueous micellar solution as a function solvent composition and of pH (see structure, Figure 1). As the DMF concentration is lowered and replaced by aqueous micellar solution, E(1/2) values become more positive. In 95% aqueous micellar solution, the complex exhibits quasi-reversible electrochemistry. As the pH is decreased from 9 to 4, the E(12) values for 1 become more negative. The IR asymmetric stretch of the Mo-oxo bond in 1 increases in frequency with decreasing pH. The relevance of this work to the understanding of molybdenum hydroxylase enzymes is underscored, and the effectiveness of solubilization of complexes in micellar solutions is discussed. [References: 40] <53> UI - 97111645 AU - Zheng Z AU - Long JR AU - Holm RH TI - A basis set of Re6Se8 cluster building blocks and demonstration of their linking capability: Directed synthesis of an Re12Se16 dicluster. SO - Journal of the American Chemical Society Vol 119(9) (pp 2163-2171), 1997. AB - A previously developed solid-state route (dimensional reduction) has led to the first molecular clusters containing the face-capped octahedral[Re6(mu3-Q)8]2+ core (Q = S, Se). Among these is the protonated cluster [Re6Se7(SeH)I6]3-, whose substitution reactions have been examined in an effort to create a set of site-differentiated precursors for forming multicluster assemblies. Reaction with Et3P under reflux with different conditions of reactant mole ratio and time affords the clusters fac-[Re6Se8(PEt3)3I3]1- (2), trans- (3) and cis-[Re6Se8(PEt3)4I2] (4), [Re6Se8(PEt3)51]1+ (5), and [Re6Se8(PEt3)6]2+ (6). The synthesis of fully substituted 6 in quantitative yield required the forcing conditions of 20 equiv of phosphine in refluxing DMF for 3 days. Reaction of 4 with AgBF4 in dichloromethane/acetonitrile gave cis-[Re6Se8(PEt3)4(MeCN)2]2+ (7); a similar reaction of 5 yielded [Re6Se8(PEt3)5(MeCN)]2+ (8) and that of [Re6Se7(SeH)I6]3- led to fully substituted [Re6Se8(MeCN)6]2+ (9). The structures of clusters 2-9 as Bu4N+ (2), iodide (5), SbF6- (7), or BF4- (6, 8, 9) salts were proven by X-ray crystallography. No significant variance was observed in the face-capped geometry of the core when bound by iodine, phosphine, and nitrile ligands alone or in combination. Terminal Re-P/I/N bond lengths were similarly independent of coligands. The combination of ligands of different lability in clusters 2-9 should make them of considerable utility in producing linked cluster assemblies/materials wherein labile ligands are displaced by bridging ligands. The simplest of these reactions, the direct coupling of two [Re6Se8]2+ cluster cores, is demonstrated here. When thermolyzed at 180 [degree] C for 24 h under dynamic vacuum, the compounds [8]X2 (X = BF4-, SbF6-) lose acetonitrile and condense to form two new compounds containing the dicluster [Re12Se16(PEt3)10]4+ (10), whose structure has been established by X-ray methods. This cluster is composed of two [Re6Se8]2+ portions which are centrosymmetrically connected by two Re-(mu4-Se) bonds to form a rhomboidal Re2Se2 unit. The bridge bonds are ca. 0.1 [Angstrom] longer than the Re-(mu3-Se) bonds of the remainder of the core; they have the same value as in the bridging rhombs present in the two-dimensional phase Re6Se8Cl2, which is a precursor solid to molecular [Re6Se8]2+ clusters by dimensional reduction. The synthesis of 10 is directed by the structure of 8, which can give only one logical product upon deligation of acetonitrile. The synthesis concept is potentially extendable to other types of oligomerized clusters. [References: 22] <54> UI - 97101886 AU - Whelton BD AU - Peterson DP AU - Moretti ES AU - Mauser RW AU - Bhattacharyya MH IN - B.D. Whelton, Department of Chemistry/Biochemistry, M.S. No. 74, Eastern Washington University, 526 5th Street, Cheney, WA 99004-2431; United States of America. TI - Kidney changes in multiparous, nulliparous and ovariectomized mice fed either a nutrient-sufficient or -deficient diet containing cadmium. SO - Toxicology Vol 119(2) (pp 123-140), 1997. AB - As a simulation of the etiological factors known for Itai-Itai disease, a syndrome characterized by renal dysfunction and osteomalacia in its Japanese victims, female mice were subjected to the individual and combined stresses of dietary Cd, nutrient-deficient diet, multiparity and ovariectomy. Renal function as affected by the etiological factors was periodically evaluated by determination of protein, amino acid, glucose and Cd concentrations in urine; periodic changes in skeletal Ca status were assessed relative to current renal function. Renal metabolism of Cd, Zn and Cu was also examined. At age 68 days, female mice were given nutrient-sufficient (+) or -deficient (-), purified diets containing either 0.25 (environmental), 5, or 50 ppm Cd as CdCl2; the nutritional composition of (-) diet simulated that of food consumed by Japanese victims of Itai-Itai disease. At age 70 days, half of the females began a breeding regimen of six consecutive, 42-day rounds of pregnancy/lactation (PL mice); the remainder were maintained as virgin, non-pregnant controls (NP mice). Limited numbers of PL and NP mice were sacrificed at the end of each reproductive round. PL(+) mice taken in a given round had successively borne litters in that round and all preceding ones. PL(-) females taken at the end of round (R)-1, -2 and -3 had successively borne litters through those rounds; those taken at the end of R-5 or R-6 had nonsuccessively borne litters in four of five or three of six rounds, respectively. At the conclusion of the 252-day reproductive period, remaining females entered the 392-day, post-reproductive phase of the experiment. At age 546 days (mid-R-12), PL females having successfully borne at least three litters were ovariectomized (OV) to mimic human menopause; at the same time, NP females were either ovariectomized or sham-operated (SO). After surgery, all females were maintained to age 714 days (mid-R-16), then sacrificed. Spot urine samples were taken from individual mice at the end of most reproductive rounds (R-2 [right arrow] 6), prior to surgery (mid-R-10), and prior to final sacrifice (late-R-15); samples were also collected via metabolism cages at the end of R-10. Food consumption, monitored on a weekly basis over the first nine rounds, was generally not significantly affected by dietary Cd level or nutrient deficiencies in females of the same reproductive status; consumption was increased about 2.5-fold in PL versus NP groups during the reproductive period and about 1.4-fold during the post-reproductive period. At each of the three dietary Cd levels and after all reproductive rounds, mean renal Cd concentrations were 1.2- to 5.6-fold higher in PL than NP mice. After six reproductive rounds, renal Cd concentrations in PL(+) and (-) groups exposed to 50 ppm Cd had reached 155 and 179 mug Cd/g kidney, respectively. Although these levels fell within a concentration range (145-200 mug Cd/g) where cadmium-induced renal dysfunction could be anticipated, no significant, Cd-dependent changes in mean urinary amino acid or protein concentrations were found. Moreover, among the same population, a 12% incidence of elevated urinary Cd (<= 250 ng/ml) was noted, however none of the affected individuals exhibited depressed total calcium content (TCa) or calcium:dry weight ratios (Ca:DW) for femur. Such results suggested that the Cd-induced, skeletal demineralization observed in mice during the reproductive period (Bhattacharyya et al., Toxicology 1988a; 50: 193-204; Whelton et al., Toxicology 1994; 91: 235-251) likely occurred in the general absence of cadmium-induced renal dysfunction. By the end of the post-reproductive period, the incidence of elevated urinary Cd increased to 26% among ovariectomized females; of these, 89% with urinary Cd <= 345 ng/ml exhibited decreases in TCa and/or Ca:DW values for femur or lumbar vertebrae that exceeded one S.D. of their group mean. Such results suggested that skeletal demineralization observed at this time (Whelton et al., Toxicology 1997a; 119: 103-121) likely occurred, for at least a portion of the population, in the presence of an ovariectomy-enhanced, cadmium-induced nephrotoxicity. During the reproductive period, small increases in Zn and Cu concentrations (ca. 1.8- and 1.5-fold, respectively) were observed for kidneys of (-) diet mice with very large increases in renal Cd concentrations (ca. 7700-fold) analogous to results previously found for (+) diet mice(Bhattacharyya et al., Toxicology 1988b; 50: 205-215). A threshold Cd concentration below which the concentration of Zn was relatively constant and independent of Cd concentration was identified (13.6 mug Cd/g kidney); no similar threshold could be observed for Cu. At the end of six rounds, less Zn was found in the kidneys of PL(-) mice exposed to Cd at the 50 than 5 ppm level, however more Cu was found in the kidneys of both NP and PL(-) mice. [References: 29] <55> UI - 97092219 AU - Karabocek S AU - Guner S AU - Karabocek N TI - Models for copper-proteins: Structure and properties of dimeric copper(I) and (II) complexes of a tetraamino-tetrathioether ligand. SO - Journal of Inorganic Biochemistry Vol 66(1) (pp 57-61), 1997. AB - Reaction of the binucleating ligand 6,6'-bis(5'-amino-3, '4'-benzo-2'- thiapentyl)-1, 11-diamino-2, 3:9,10-dibenzo-4,8-ditbiaundecane (H4L) with copper(II) salts in dried methanol (MeOH) results in the isolation of the mixtures of copper(I) and (II) complexes with Cl- and CIO4- counterions. The major products were the copper(I) complexes obtained pure after recrystallization from DMSO-MeOH. The ligands lose four protons from the amine functions to form copper(I) complexes of the general formula (Cu2L)X2, where X = Cl- C104-. The complexes were oxidized to (Cu2L)X4 with hydrogen peroxide in DMF. Cu(NO3)2, on the other band, gave [Cu2(H4L)(NO3)2](NO3)2. The structure consists of two copper(I) and copper(II) atoms, each of which is coordinated through two thioether and two primary amine atoms. The two copper sites are linked through a saturated spiro carbon atom. The copper complexes were characterized by elemental analyses, molar conductivities, magnetic moments, and spectra (UV/-Vis, IR). [References: 33] <56> UI - 97092212 AU - Rodriguez-Arguelles MC AU - Ferrari MB AU - Fava GG AU - Pelizzi C AU - Pelosi G AU - Albertini R AU - Bonati A AU - Dall'Aglio PP AU - Lunghi P AU - Pinelli S IN - Prof. G.G. Fava, DCGI, CSSD del CNR, Universita di Parma, Viale delle Scienze, 43100 Parma; Italy. TI - Acenaphthenequinone thiosemicarbazone and its transition metal complexes: Synthesis, structure, and biological activity. SO - Journal of Inorganic Biochemistry Vol 66(1) (pp 7-17), 1997. AB - The reaction of iron, nickel, copper, and zinc chlorides or acetates with acenapbthenequinone thiosemicarbazone, Haqtsc leads to the formation of novel complexes that have been characterized by spectroscopic studies (NMR, IR) and biological properties. The crystal structures of the free ligand Haqtsc 1 and of the compound [Ni(aqtsc)2]. DMF 2, have also been determined by X-ray methods from diffractometer data. In 1, the conformation of the two nonequivalent molecules is governed by intramolecular hydrogen bonds, while an intermolecular hydrogen bond is responsible for dimer-like groups formation. In 2, the coordination geometry about nickel is distorted octabedral, and the two ligand molecules are terdentate monodeprotonated. Biological studies have shown that, for the first time at least up the used doses, a free ligand is active both in the inhibition of cell proliferation and in the induced differentiation on Friend erythroleukemia cells. [References: 22] <57> UI - 97082543 AU - Gosmini C AU - Nedelec JY AU - Perichon J TI - Electrosynthesis of 3-thienylzinc bromide from 3-bromothiophene via a nickel catalysis. SO - Tetrahedron Letters Vol 38(11) (pp 1941-1942), 1997. AB - 3-Thienylzinc bromide is prepared under mild conditions by electroreduction of a DMF solution of 3-bromothiophene, zinc bromide, and a catalytic amount of nickel-bipyridine complex using a magnesium rod as sacrificial anode. The resulting organometallic is then coupled with aryl halides using a palladium catalysis. [References: 7] <58> UI - 96319600 AU - London RE AU - Gabel SA IN - Laboratory of Molecular Biophysics, National Inst. of Envtl. Health Sci., Box 12233, Research Triangle Park, NC 27709; United States of America. TI - Mg2+ and other polyvalent cations catalyze nucleotide fluorolysis. SO - Archives of Biochemistry & Biophysics Vol 334(2) (pp 332-340), 1996. AB - The reaction of fluoride with adenosine triphosphate has been studied as a nonenzymatic analog of the pyruvate kinase-catalyzed fluorokinase reaction. The production of fluorophosphate, as well as adenosine 5'-O-fluorophosphate (FAMP) and adenosine 5'-O(2-fluorodiphosphate) (betaFADP) was found to be dependent on the presence of polyvalent metal ions. All ions tested showed significant activity. Two catalytic regimes for the cations could be distinguished: a less specific enhancement of product formation at lower fluoride/cation ratios, and a considerably more active and specific (for fluorophosphate production) enhancement at high fluoride/cation ratios. A comparison of the results with studies of cation-catalyzed nucleotide hydrolysis indicates that the fluorolysis mechanisms are analogous to the hydrolysis by hydroxyl ions observed at high pH. In addition to these nonenzymatic studies, experiments performed using several commercially available kinases indicated significant fluorokinase activity for two: glycerokinase and acetate kinase, although the activities were much below that of pyruvate kinase. With the exception of the concentrations used in these studies, these reactions proceed under physiological conditions, yielding products at sufficient concentrations to be readily detected by 19F NMR spectroscopy. <59> UI - 96198582 AU - El-Batouti M AU - Zaghloul AA AU - Hanna MT IN - Chemistry Department, Faculty of Science, Alexandria University, Alexandria; Egypt. TI - A kinetic study of the copper exchange reaction on a sodium-montmorillonite clay mineral in acetonitrile and dimethylformamide. SO - Journal of Colloid & Interface Science Vol 180(1) (pp 106-110), 1996. AB - The kinetics of Cu2+ exchange on a Na-montmorillonite clay mineral were investigated at three temperatures, in acetonitrile (AcN) and dimethylformamide (DMF) solvents. The solvent effects on the reaction rate were discussed. The thermodynamic activation parameters were calculated and discussed in terms of the solvation effects. <60> UI - 95246709 AU - Loomba K AU - Pandey GS IN - School of Studies in Chemistry, Pt. Ravishankar Shukla University, Raipur 492 010; India. TI - Fabrication of copper-iron galvanic couples using wastes: Application in removal of selected toxic metal ions. SO - Water Treatment Vol 10(1) (pp 69-74), 1995. AB - Copper-iron galvanic couples have been fabricated using iron-strips discarded as packing wastes and copper-pickled liquor discharged as wastewaters from a copper-wire plant. Two patterns of the couples were prepared. In the first pattern, a single continuous copper band covering half the length of the iron strips was obtained. In the second pattern, copper coating was done in alternate bands on both sides of the iron strips. Pure iron strips (uncoated) were also used. When the strips were packed separately in glass column and solutions of toxic metal ions [Hg (II), Pb (II), Sn(II), Ni(II) and Cd(II)] were flowed at controlled rates to obtain total removal of the respective metal ions from the outflowing solution, significant increase in the rates of removal was observed in cases of the copper-iron couples. The removal rates were increased by several-fold in the case where the copper coating of the iron strips was done in alternate bands. <61> UI - 95084850 AU - Gokhale AS AU - Venkateswaran G AU - Moorthy PN IN - Applied Chemistry Division, Bhabha Atomic Research Centre, Trombay, Bombay 400 085; India. TI - Waste treatment by ion-exchange and precipitation methods after LOMI decontamination. SO - Waste Management Vol 14(8) (pp 703-708), 1994. AB - Conventional polystyrene-based strong acid cation and strong base anion exchangers have been evaluated for the retention of 60Co from vanadium based low oxidation-state metal ion (LOMI) decontamination formulation. Cation exchange treatment results in decontamination factors (DFs) of 8-40 with respect to 60Co if the LOMI solution is treated immediately after decontamination but yields lower DFs of 3-4 if it is stored for >24 h under ambient conditions. In both cases, anionic treatment of the cation column effluent gives DFs in the range 45-400. These results point to the differential speciation of 60Co in fresh and stored LOMI solutions and hence the necessity of having both cation and anion exchange treatments for the near complete removal of 60Co. Coprecipitation with MnO2 obtained by mixing the used LOMI solution with the required amounts of alkaline KMnO4 employed for pretreating the oxide surfaces was also found to be an effective method for 60Co removal. From the point of view of total activity removal, the precipitation method was less efficient than ion-exchange method. <62> UI - 94365687 AU - Rubio LA AU - Grant G AU - Dewey P AU - Bremner I AU - Pusztai A IN - Rowett Research Institute,Bucksburn, Aberdeen AB2 9SB; United Kingdom. TI - The intestinal true absorption of 65Zn in rats is adversely affected by diets containing a faba bean (Vicia faba L.) nonstarch polysaccharide fraction. SO - Journal of Nutrition Vol 124(11) (pp 2204-2211), 1994. AB - The effects on the absorption of 65Zn by two varieties of raw faba bean (Vicia faba L., minor) or seed components that may interfere with mineral metabolism in the gut, have been studied in growing rats. In bean diets all protein was supplied by the meals, and the fractions were tested by incorporating them in control diet at the same levels as they occur in the seeds. Absorption of 65Zn was also measured in rats fed dephytinized bean meal produced by including phytase in the diet. Rats were pair-fed diets' supplemented with amino acids and minerals to target requirements and containing 40 mg Zn/kg diet. True absorption of Zn was 50-70% lower in rats fed diets containing both cultivars of faba bean meals than in those fed the control diet. Although soluble nonstarch polysaccharides caused a significant reduction in the absorption of Zn, this effect disappeared after the removal of phytate by demineralization. In contrast, despite its negligible content of phytate, the insoluble nonstarch polysaccharides in the cell wall fraction of the cotyledon accounted for most of the reduction in Zn absorption in rats fed the faba bean diets. Addition of phytic acid to the control diet significantly reduced the absorption of 65Zn-but only from 44 to 36%. Moreover, the increase in the absorption of Zn was similarly small, from 21% to 29%, with the addition of phytase to the faba bean diet. These results suggest that, in addition to phytic acid, the insoluble nonstarch polysaccharides present in the cell walls of the cotyledon in Vicia faba seeds are mainly responsible for the lower Zn availability in rats fed faba bean diets. <63> UI - 94277494 AU - Shin S-Y AU - Calvisi EG AU - Beaman TC AU - Pankratz HS AU - Gerhardt P AU - Marquis RE IN - Microbiology/Immunology Department, University of Rochester,Rochester, NY 14642-8672; United States of America. TI - Microscopic and thermal characterization of hydrogen peroxide killing and lysis of spores and protection by transition metal ions, chelators, and antioxidants. SO - Applied & Environmental Microbiology Vol 60(9) (pp 3192-3197), 1994. AB - Killing of bacterial spores by H2O2 at elevated but sublethal temperatures and neutral pH occurred without lysis. However, with prolonged exposure or higher concentrations of the agent, secondary lytic processes caused major damage successively to the coat, cortex, and protoplast, as evidenced by electron and phase contrast microscopy. These processes were also reflected in changes in differential scanning calorimetric profiles for H2O2-treated spores. Endothermic transitions in the profiles occurred at lower temperatures than usual as a result of H2O2 damage. Thus, H2O2 sensitized the cells to heat damage. Longer exposure to H2O2 resulted in total disappearance of the transitions, indicative of major disruptions of cell structure. Spores but not vegetative cells were protected against the lethal action of H2O2 by the transition metal cations Cu+, Cu2+, Co2+, Co3+, Fe2+, Fe3+, Mn2+, Ti3+, and Ti4+. The metal chelator EDTA was also somewhat protective, while o-phenanthroline, citrate, deferoxamine, and ethanehydroxydiphosphonate were only marginally so. Superoxide dismutase and a variety of other free-radical scavengers were not protective. In contrast, reducing agents such as sulfhydryl compounds and ascorbate at concentrations of 20 to 50 mM were highly protective. Decoating or demineralization of the spores had only minor effects. The marked dependence of H2O2 sporicidal activity on moderately elevated temperature and the known low reactivity of H2O2 itself suggest that radicals are involved in its killing action. However, the protective effects of a variety of oxidized or reduced transition metal ions indicate that H2O2 killing of spores is markedly different from that of vegetative cells. <64> UI - 94245151 AU - Sanders II CR IN - Department Physiology and Biophysics, Case Western Reserve University, School of Medicine,Cleveland, OH 44106; United States of America. TI - Qualitative comparison of the bilayer-associated structures of diacylglycerol and a fluorinated analog based upon oriented sample NMR data. SO - Chemistry & Physics of Lipids Vol 72(1) (pp 41-57), 1994. AB - sn-1,2-Dimyristoylglycerol (DMDAG) and sn-1,2-dimyristoyl-3-fluoropropanediol (DMFPD) were synthesized in carbonyl 13C-labeled and acyl chain perdeuterated forms. These compounds were reconstituted at low levels into both randomly dispersed dimyristoylphosphatidylcholine (DMPC) bilayers and magnetically orientable DMPC media. Samples were subjected to NMR analysis, leading to a substantial body of 2H quadrupolar splitting, 13C-13C and 13C-19F dipolar coupling and 13C chemical shift anisotropy data for both compounds. A number of measurements were also made for DMPC. The data acquired from magnetically oriented samples were found to be undesirably affected by the presence of artifacts related to the experimental use of the oriented lipid media. However, it was possible to draw a number of qualitative conclusions from the data and to correct the data so that they may ultimately prove useful in quantitative structural analyses of bilayer-associated DMDAG and DMFPD. Comparison of the DMDAG data with corresponding measurements for DMPC suggests a high degree of similarity between the two compounds within bilayers composed primarily of L(alpha) phase phosphatidylcholine, consistent with previous work. Comparison of the data for DMDAG and DMFPD suggests that the hydroxyl proton of DMDAG is involved in hydrogen bonding interactions, which appear to be largely responsible for maintaining the orientational inequivalence of its two acyl chains. Bilayer-associated DMFPD also appears to exhibit a higher degree of whole-molecule disorder than DMDAG, again suggestive of an important structural role for the hydroxyl proton of DMDAG. Finally, comparison of 13C-NMR data for oriented DMPC in the presence and absence of low levels of DMDAG and DMFPD indicated that neither compound induces a significant change in the averaged conformational state of DMPC comprising the bilayer matrix of the oriented samples. <65> UI - 94222409 AU - Manessi-Zoupa E AU - Perlepes SP AU - Hondrellis V AU - Tsangaris JM IN - Laboratory of Inorganic Chemistry, Department of Chemistry, University of Patras,26500 Patra; Greece. TI - Transition metal complexes of N-(2-benzamide)pyridine-2'-carboxamide, a potentially tridentate ligand containing one secondary and one primary amide group: Preparation and characterization in the solid state. SO - Journal of Inorganic Biochemistry Vol 55(3) (pp 217-233), 1994. AB - The synthesis of N-(2-benzamide)pyridine-2'-carboxamide (LH2) is reported along with its employment as a ligand. The new complexes [MCl2(LH2)2] . DMF (M = Co, Ni), [Cu2Cl4(LH2)2] . DMF, [CuCl2(LH2)2], [Co(OH)(LH)](n) . nH2O, [M2(OH)2(H2O)(x)(LH)2](M = Ni, Cu; x = 4, 2), [M(LH)2] . xH2O (M = Ni, Cu; x = 0, 1), [Ni(H2O)2(LH)2] . H2O, and [CuCl(LH)](n), where DMF = N,N-dimethylformamide, have been isolated. The complexes were characterized by elemental analyses, conductivity measurements, x-ray powder patterns, thermal methods, variable-temperature magnetic susceptibilities, and spectroscopic (IR and far-IR, ligand field, ESR) studies. A variety of stereochemistries is assigned for the complexes in the solid state. The neutral ligand acts as a bidentate chelating agent with ligated atoms being the ring nitrogen and the secondary amide oxygen; the LH- ion behaves as a bidentate chelating N(ring), N(secondary amide) or as a adentate N(ring), N(secondary amide), O(primary amide) ligand depending mainly on the reaction conditions. <66> UI - 94174214 AU - Chowdhury N AU - Singh R IN - Punjab Agricultural University, Dept Veterin Parasitology Physiology, College of Veterinary Science,Ludhiana 141 004, Punjab; India. TI - Distribution of some elements in hydatid cysts of Echinococcus granulosus from buffalo (Bubalus bubalis). SO - Journal of Helminthology Vol 67(2) (pp 112-114), 1993. AB - Distribution of some elements during development of endogenous daughter (hydatid) cysts of Echinococcus granulosus of buffalo origin was determined by atomic absorption spectrophotometry. These analyses showed that the distribution of copper and cobalt was highest in the smallest cysts. These elements gradually decreased in the cysts as they enlarged. The distribution of zinc, iron and manganese was very high in the smallest cysts in comparison to copper and cobalt, but these three elements decreased greatly in larger cysts. Iron and manganese were the only two elements found in very high concentrations in 'thin -walled' cysts. Like all other elements both calcium and magnesium decreased as the cysts increased in size. In the thin-walled cysts magnesium increased by four times initially and this was followed by a two-fold 'influx' of calcium in the 'white-spots' in the above cysts. The significance of these findings is discussed in relation to earlier works. <67> UI - 94040040 AU - Roth JA AU - Dakoji SR AU - Hughes RC AU - Carmody RE IN - Department of Chemistry, Northern Michigan University,Marquette, MI 49855; United States of America. TI - Hydrogenolysis of polychlorinated biphenyls by sodium borohydride with homogeneous and heterogeneous nickel catalysts. SO - Environmental Science & Technology Vol 28(1) (pp 80-87), 1994. AB - The hydrogenolysis (hydrodechlorination) of a series of pure PCB congeners with sodium borohydride was studied. In the absence of nickel compounds, very little reaction occurred, but in the presence of solid Raney-type nickel or in the presence of a soluble Ni(0)triphenylphosphine complex, extensive hydrogenolysis occurred at ambient temperatures in DMF. The selectivity of one congener versus another was studied and found to be low. The selectivity for 2-, 3-, and 4-chloro displacement from di- and trichlorobiphenyls in the presence of Ni(0) complexes, however, was found to be high. The selectivities are interpreted with respect to the known mechanism of oxidative addition of aryl halides with Ni(0) complexes. <68> UI - 93266820 AU - Kiyohara C AU - Saitoh K AU - Suzuki N IN - Department of Chemistry, Faculty of Science, Tohoku University,Sendai, 980 Miyagi; Japan. TI - Micellar electrokinetic capillary chromatography of haematoporphyrin, protoporphyrin and their copper and zinc complexes. SO - Journal of Chromatography Vol 646(2) (pp 397-403), 1993. AB - The micellar electrokinetic chromatographic separation of haematoporphyrin IX (HP) and protoporphyrin IX (PP) in the forms of free acids and of metal complexes with zinc or copper is successful in a mixture of a micellar solution of sodium dodecyl sulphate (SDS) at pH 11 and dimethylformamide (10:2, v/v). All the porphyrins migrate in the direction of the electric field, i.e., from the positive end towards the grounded end of the capillary. The migration time of each porphyrin increases with increasing concentrtion of DMF in the carrier solution. The capacity factor calculated for the distribution of each porphyrin compound between the SDS micelles and the bulk solution varies nearly linearly with the concentration of the SDS micelles. The migration sequence, that is, the increasing order of migration time, for the porphyrins is Zn(HP) < H2HP < Cu(HP) < Zn(PP) < H2PP < Cu(PP). <69> UI - 93051685 AU - Drake DR AU - Grigsby W AU - Cardenzana A AU - Dunkerson D IN - Dows Institute for Dental Research, College of Dentistry, University of Iowa,Iowa City, IA 52242; United States of America. TI - Synergistic, growth-inhibitory effects of chlorhexidine and copper combinations on Streptococcus mutans, Actinomyces viscosus, and Actinomyces naeslundii. SO - Journal of Dental Research Vol 72(2) (pp 524-528), 1993. <70> UI - 93046946 AU - Bauer PD AU - Trapp C AU - Drake D AU - Taylor KG AU - Doyle RJ IN - Microbiology/Immunology Department, University of Louisville,Louisville, KY 40292; United States of America. TI - Acquisition of manganous ions by mutans group streptococci. SO - Journal of Bacteriology Vol 175(3) (pp 819-825), 1993. AB - The cariogenic bacteria Streptococcus sobrinus and S. cricetus were shown to have an absolute requirement for manganous ion in order to bind glucans or to adhere to glass in the presence of sucrose. The bacteria possessed a reasonably high affinity transport system for 54Mn2+, yielding a K(m) of about 12 muM. The V(max) for uptake of 54Mn2+ in S. sobrinus was increased when the bacteria were grown in Mn-depleted medium, but the K(m) remained the same. There was no evidence for two Mn2+ uptake systems, commonly observed for many bacteria. Ions such as Ca2+, Co2+, Co3+, Cu2+, Fe2+, Fe3+, Hg2+, Mg2+, Ni2+, and Zn2+ did not inhibit the uptake of 54Mn2+ by the bacteria, although Cd2+ was a potent inhibitor. Fractionation experiments showed that manganese was distributed in protoplasts (67%) and in the cell wall (33%). Approximately 80% of the 54Mn2+ in S. sobrinus was rapidly exchangeable with nonradioactive Mn2+. Electron spin resonance experiments showed that all of the manganese was bound or restricted in mobility. Proton motive force-dissipating agents increased the acquisition of 54Mn2+ by the streptococci, probably because the wall became more negatively charged when the cell could no longer produce protons. <71> UI - 92270651 AU - Lu-Lu AU - Singh JS AU - Galperin MY AU - Drake D AU - Taylor KG AU - Doyle RJ IN - Microbiology/Immunology Department, Academic Health Center, University of Louisville,Louisville, KY 40292; United States of America. TI - Chelating agents inhibit activity and prevent expression of streptococcal glucan-binding lectins. SO - Infection & Immunity Vol 60(9) (pp 3807-3813), 1992. AB - Several of the cariogenic mutans streptococci produce cell wall-associated glucan-binding lectins (GBLs). The lectins bind alpha-1,6-linked glucans and have no affinity for other polysaccharides or anomeric linkages. When citrate or lactate was included in the growth medium, expression of the activities of the GBLs of Streptococcus cricetus and S. sobrinus was prevented. Furthermore, chelating agents, including citrate, lactate, EDTA, and acetylacetone, were able to reversibly inhibit glucan-induced aggregation of GBL+ streptococci. In addition, the chelating agents prevented sucrose- dependent streptococcal adhesion to glass surfaces and dispersed preformed adherent masses of the streptococci. Neither citrate nor other chelating agents modified the activities of glucosyltransferases. Expression of the lectin could only be achieved by the addition of manganous ion to the growth medium. Chloramphenicol and other metabolic inhibitors prevented synthesis of GBL in cells obtained from manganese-deficient medium and shifted to manganous ion-sufficient medium. The GBL may be a manganoprotein, the manganese of which may be perturbed, but not removed, by chelating agents. During synthesis of the GBL, manganous ion may be required in order for the protein to achieve an active conformation. Citrate or other chelating agents may have promise as anticaries agents. <72> UI - 92130681 AU - Diamadopoulos E AU - Samaras P AU - Sakellaropoulos GP IN - Chemical Process Eng Res Insti, Aristotle University of Thessa, P.O. Box 1520,54006 Thessaloniki; Greece. TI - The effect of activated carbon properties on the adsorption of toxic substances. SO - Water Science & Technology Vol 25(1) (pp 153-160), 1992. AB - The objectives of this work were to relate the activated carbon properties to its adsorptive capacity. The activated carbon needed was produced in the lab from Greek lignite coal. Subsequently, adsorption studies were performed in order to evaluate the efficiency of the various activated carbons to remove toxic substances from water. Two organic substances were used. These were phenol and fulvic acid. Additionally, the adsorption of arsenic (V) was, also, investigated. It was found that the adsorptive capacity of the activated carbons depended primarily on the ash content and the compound. The capacity of the carbon to remove phenol, expressed as mg of phenol removed per g of activated carbon (carbon loading), decreased linearly as the amount of ash in the activated carbon increased. Ash-free activated carbons could adsorb 4 times as much phenol as the activated carbons with a high ash content. On the other hand, fulvic acid and arsenic adsorbed poorly on the ash-free activated carbons. Even for the high surface area activated carbons (over 1000 m2/g), the quantity of fulvic acid or arsenic adsorbed was significantly less than that exhibited by the high ash activated carbons (maximum surface area measured hardly exceeded 300 m2/g). As the amount of ash in the carbon increased, the carbon loading increased as well, up to a certain level, beyond which the amount of ash played no significant role. The beneficial role of ash was explained by the ability of the fulvic acid and arsenic to interact with metal oxides and metal ions, which constitute a significant fraction of the ash. <73> UI - 91205917 AU - Hamilton CL AU - Ma L AU - Renner MW AU - Scott RA IN - Department of Chemistry, University of Georgia,Athens, GA 30602; United States of America. TI - Ni(II) and Ni(I) forms of pentaalkylamide derivatives of cofactor F340 of Methanobacterium thermoautotrophicum. SO - Biochimica et Biophysica Acta - General Subjects Vol 1074(2) (pp 312-319), 1991. AB - A series of pentaalkylamide forms of F430 and of its 12,13-diepimer have been generated and characterized. Carbodiimide-assisted N-hydroxysulfosuccinimide activation of all five peripheral carboxylates of the F430 macrocycle allows nucleophilic attack by a number of primary amines (RNH2, R- = CH3-, CH3CH2-, CF3CH2-, CH3(CH2)3-) generating the pentaalkylamide derivatives. The identity of each derivative has been verified by fast-atom bombardment mass spectrometry (FAB-MS). The solubility of these derivatives in aprotic organic solvents varies as the amine alkyl substituent (R-) is changed. Electrochemical measurements have shown that the Ni(II/I) reduction potentials in N,N-dimethylformamide (DMF) are [similar] -1 V (Ag/AgCl). Reduction by sodium amalgam in THF generates the Ni(I) form of the F430 diepimer pentabutylamide. The visible and EPR spectra of this Ni(I) species are very similar to the corresponding spectra of Ni(I) F430M (Jaun, B. and Pfaltz, A. (1986) J. Chem. Soc. Chem. Commun. 1327-1329.). <74> UI - 91041858 AU - Szabo G AU - Wedgwood AJ AU - Bulman RA IN - National Radiological, Protection Board,Didcot OX11 0RQ; United Kingdom. TI - Comparison and development of new extraction procedures for 239Pu, Ca, Fe and Cu organic complexes in soil. SO - Journal of Environmental Radioactivity Vol 13(3) (pp 181-189), 1991. AB - Two new extraction methods - the silylation of the organic constituents of soil with trimethylchlorosilane (TMCS) and triethylchlorosilane (TECS) in the presence of dimethylformamide (DMF) - have been developed for mobilization of the organic complexes of Ca, Fe, Cu and Pu which might exist in some soils. By silylation of the carboxylic, phenolic, alcoholic and perhaps the amino moieties of humic and fulvic acids (the principal organic constituents of soils) the authors have modified the solubility of the humic substances with perhaps a minimum perturbation of the humate-metal ion complexes. These new extraction procedures, which use a non-aqueous solvent, have been compared with a variety of aqueous extraction procedures (sodium hydroxide, 1 M potassium chloride and diethylenetriaminopentaacetic acid solution) and found to be superior in the release of the elements from soils. <75> UI - 90329111 AU - Miura J AU - Arima S AU - Satake M IN - Faculty of Engineering, Fukui University, Fukui 910; Japan. TI - Tetradecyldimethylbenzylammonium thiocyanate adsorbent supported on naphthalene for the preconcentration and determination of cobalt in aluminium alloys and steels using atomic absorption spectrometry. SO - Analytica Chimica Acta Vol 237(1) (pp 201-206), 1990. AB - A solid ion-pair material produced from tetradecyldimethylbenzylammonium chloride (TDBA) and ammonium thiocyanate on naphthalene provides a simple, rapid and selective technique of preconcentrating cobalt from up to 200 ml of aqueous solution. Cobalt reacts with sodium 1-nitroso-2-naphthol-3,6-disulphonate (nitroso-R salt) to form a brown, water-soluble chelate anion. The chelate anion forms a water-insoluble Co-nitroso-R salt-TDBA complex on naphthalene packed in a column and trace cobalt is quantitatively retained on the naphthalene in the pH range 2.7-11.0 at a flow-rate of 2 ml min-1. The solid mass is stripped from the column with 5 ml of dimethylformamide (DMF) and cobalt is measured by atomic absorption spectrometry (AAS) at 241 nm. The calibration graph is linear over the concentration range 0.5-15 mug Co in 5 ml of dimethylformamide solution. Seven replicate determinations of 9 mug of cobalt gave a mean absorbance of 0.095 with a relative standard deviation of 1.7%. The sensitivity for 1% absorption was 0.0834 mug ml-1 (0.240 mug ml-1 for direct AAS on the aqueous solution). The proposed method was utilized for the determination of cobalt in standard aluminium alloys and steel samples. <76> UI - 90327487 AU - Kruger H-J AU - Holm RH IN - Department of Chemistry, Harvard University, Cambridge, MA 02138; United States of America. TI - Stabilization of trivalent nickel in tetragonal NiS4N2 and NiN6 environments: Synthesis, structures, redox potentials, and observations related to [NiFe]-hydrogenases. SO - Journal of the American Chemical Society Vol 112(8) (pp 2955-2963), 1990. AB - The influence of ligand structure on Ni(III)/Ni(II) redox potentials has been examined in order to elucidate those factors that lead to unusually low values for this couple, such as are found in [NiFe]-hydrogenases. The compound (Et4N)2[Ni(pdtc)2] [3, pdtc = pyridine-2,6- bis(monothiocarboxylate)(2-)] is readily prepared and crystallizes in monoclinic space group C2/c with a = 19.036 (4) [Angstrom] , b = 11.231 (2) [Angstrom] , c = 16.588 (3) [Angstrom] , beta = 101.01 (1) [degree] , and Z = 4. Reaction of 3 with iodine in methanol and addition of (Ph3PCH2Ph)Br affords green (Ph3PCH2Ph)]Ni(pdtc)2] (4), which crystallizes in monoclinic space group P21/n with a = 10.181 (1) [Angstrom] , b = 21.033 (4) [Angstrom] , c = 16.937 (3) [Angstrom] , beta = 95.02 (1) [degree] , and Z = 4. Also prepared was (Ph3PCH2Ph)[Co(pdtc)2], which is isomorphous with 4. Complexes 3 and 4 and [Co(pdtc)2]1- have tetragonally distorted octahedral structures in which the tridentate ligand binds in a meridional manner such that each species has an essentially planar MS4 fragment. The EPR properties of 4 [g perpendicular to > g parallel with, g(av) = 2.103, a(av)(61Ni) = 22 +/- 1 G] and comparative structural features with 3 and [Co(pdtc)2]1- demonstrate the Ni(III) state with a (d(z)2)1 ground state. Thus, the [three quarters] redox couple, with E( [half] ) = -0.085 V vs SCE in DMF, is a metal-centered process. [Ni(pdtc)2]2-,1- are the first pair of structurally defined Ni(II,III) complexes with anionic sulfur ligands. The previously reported Ni(II) complex [Ni(dapo)2]2- [5, dapo = pyridine-2,6-bis- (acetyloximate)(2-)] exhibited a three-membered redox series, being oxidized to [Ni(dapo)2]1- (6) and then to the known Ni(IV) complex [Ni(dapo)2] (7) at E( [half] ) = -0.735 and -0.255 V in DMF. The tetragonally distorted octahedral structure established earlier for 7 doubtless applies to 6