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Dimethyl Sulfoxide Solution (dimethyl + sulfoxide_solution)
Selected AbstractsDivanadium(V) and Trapped Valence Linear Tetravanadium(IV,V,V,IV) ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 35 2009Anindita Sarkar Abstract In an acetonitrile/water mixture, reactions of the N,N,-bis(diacetyl)hydrazine (H2diah), bis(acetylacetonato)oxidovanadium(IV) [VO(acac)2] and monodentate N -coordinating heterocycles (hc) in a 1:2:2 mol ratio provide yellow divanadium(V) complexes of formula [(hc)O2V(,-diah)VO2(hc)] (1, hc = imidazole; 2, hc = pyrazole; 3, hc = 3,5-dimethyl pyrazole). On the other hand, in the same solvent mixture reactions of the same reagents in a 1:4:2 mol ratio produce green linear tetravanadium(IV,V,V,IV) complexes of formula [(acac)2OV(,-O)VO(hc)(,-diah)(hc)OV(,-O)VO(acac)2] (4, hc = imidazole; 5, hc = pyrazole; 6, hc = 3,5-dimethyl pyrazole). The complexes 1,6 have been characterized by elemental analysis, magnetic susceptibility, and various spectroscopic and electrochemical measurements. The X-ray crystal structures of 1, 3 and 6 have been determined. In all three structures, the diazine ligand diah2, is in trans configuration. Metal-centred bond parameters are consistent with the localized electronic structure of the two trans -bent {OV(,-O)VO}3+ cores present in 6. The pentavalent metal centres in 1, 3 and 6 are in a distorted trigonal-bipyramidal N2O3 coordination environment, while the terminal tetravalent metal centres in 6 are in a distorted octahedral O6 coordination sphere. The eight-line EPR spectra of the tetravanadium species (4,6) in dimethyl sulfoxide at ambient temperature indicate the rare valence localized electronic structure in the fluid phase. All the complexes are redox active and display metal-centred electron transfer processes in dimethyl sulfoxide solution. A reduction within ,0.78 to ,0.94 V (vs. Ag/AgCl) is observed for the divanadium(V) species 1,3, while a reduction and an oxidation are observed in the potential ranges ,0.82 to ,0.90 V and 0.96 to 1.12 V (vs. Ag/AgCl), respectively, for the tetravanadium species 4,6. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Proposed mechanism of inactivating Escherichia coli O157:H7 by ultra-high pressure in combination with tert -butylhydroquinoneJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2008A.S. Malone Abstract Aims:, Investigating mechanisms of lethality enhancement when Escherichia coli O157:H7, and selected E. coli mutants, were exposed to tert -butylhydroquinone (TBHQ) during ultra-high pressure (UHP) treatment. Methods and Results:,Escherichia coli O157:H7 EDL-933, and 14 E. coli K12 strains with mutations in selected genes, were treated with dimethyl sulfoxide solution of TBHQ (15,30 ppm), and processed with UHP (400 MPa, 23 ± 2°C for 5 min). Treatment of wild-type E. coli strains with UHP alone inactivated 2·4,3·7 log CFU ml,1, whereas presence of TBHQ increased UHP lethality by 1·1,6·2 log CFU ml,1; TBHQ without pressure was minimally lethal (0,0·6 log reduction). Response of E. coli K12 mutants to these treatments suggests that iron,sulfur cluster-containing proteins ([Fe,S]-proteins), particularly those related to the sulfur mobilization (SUF system), nitrate metabolism, and intracellular redox potential, are critical to the UHP,TBHQ synergy against E. coli. Mutations in genes maintaining redox homeostasis and anaerobic metabolism were associated with UHP,TBHQ resistance. Conclusions:, The redox cycling activity of cellular [Fe,S]-proteins may oxidize TBHQ, potentially leading to the generation of bactericidal reactive oxygen species. Significance and Impact of the Study:, A mechanism is proposed for the enhanced lethality of UHP by TBHQ against E. coli O157:H7. The results may benefit food processors using UHP,based preservation, and biologists interested in piezophilic micro-organisms. [source] Synthesis of ethyl 6-aryl-4-oxo-4,6-dihydro-1(12)(13)h -pyrimido-[2,,1,:4,5][1,3,5]triazino[1,2- a]benzimidazole-3-carboxylates,JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2006Anton V. Dolzhenko The synthesis of ethyl 6-aryl-4-oxo-4,6-dihdro-1(12)(13)H -pyrimido[2,,1,:4,5][1,3,5]triazino[1,2- a]-benzimidazole-3-carboxylates (4a-p) was described via pyrimidine ring annulation to 4-aryl-3,4-dihydro[1,3,5]triazino[1,2- a]benzimidazole-2-amines (2a-p) which were obtained from 2-guanidinobenzimidazole (1). Tautomerism in the prepared compounds was investigated using nmr spectroscopy. Compounds 2a-p were found to be present in dimethyl sulfoxide solution predominantly as 3,4-dihyhydro tautomeric form. Compounds 4a-p existed in dynamic equilibrium of 1-, 12- and 13H -forms. It was found that methylation of 4a-d led to 13-methyl substituted derivatives 9a-d exclusively. [source] How to visualize the spider mite silk?MICROSCOPY RESEARCH AND TECHNIQUE, Issue 9 2009G. Clotuche Abstract Tetranychus urticae (Acari: Tetranychidae) is a phytophagous mite that forms colonies of several thousand individuals. Like spiders, every individual produces abundant silk strands and is able to construct a common web for the entire colony. Despite the importance of this silk for the biology of this worldwide species, only one previous study suggested how to visualize it. To analyze the web structuration, we developed a simple technique to dye T. urticae'silk on both inert and living substrates. Fluorescent brightener 28 (FB) (Sigma F3543) diluted in different solvents at different concentrations regarding the substrate was used to observe single strands of silk. On glass lenses, a 0.5% dimethyl sulfoxide solution was used and on bean leaves, a 0.1% aqueous solution. A difference of silk deposit was observed depending the substrate: rectilinear threads on glass lenses and more sinuous ones on bean leaves. This visualizing technique will help to carry out future studies about the web architecture and silk used by T. urticae. It might also be useful for the study of other silk-spinning arthropods. Microsc. Res. Tech. 2009. © 2009 Wiley-Liss, Inc. [source] | ||||||||||