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Sulfur Oxidation (sulfur + oxidation)
Selected AbstractsKinetic Resolution in Vanadium-Catalyzed Sulfur Oxidation as an Efficient Route to Enantiopure Aryl Benzyl Sulfoxides.CHEMINFORM, Issue 42 2006Padraig Kelly Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Biochemistry and molecular biology of lithotrophic sulfur oxidation by taxonomically and ecologically diverse bacteria and archaeaFEMS MICROBIOLOGY REVIEWS, Issue 6 2009Wriddhiman Ghosh Abstract Lithotrophic sulfur oxidation is an ancient metabolic process. Ecologically and taxonomically diverged prokaryotes have differential abilities to utilize different reduced sulfur compounds as lithotrophic substrates. Different phototrophic or chemotrophic species use different enzymes, pathways and mechanisms of electron transport and energy conservation for the oxidation of any given substrate. While the mechanisms of sulfur oxidation in obligately chemolithotrophic bacteria, predominantly belonging to Beta - (e.g. Thiobacillus) and Gammaproteobacteria (e.g. Thiomicrospira), are not well established, the Sox system is the central pathway in the facultative bacteria from Alphaproteobacteria (e.g. Paracoccus). Interestingly, photolithotrophs such as Rhodovulum belonging to Alphaproteobacteria also use the Sox system, whereas those from Chromatiaceae and Chlorobi use a truncated Sox complex alongside reverse-acting sulfate-reducing systems. Certain chemotrophic magnetotactic Alphaproteobacteria allegedly utilize such a combined mechanism. Sulfur-chemolithotrophic metabolism in Archaea, largely restricted to Sulfolobales, is distinct from those in Bacteria. Phylogenetic and biomolecular fossil data suggest that the ubiquity of sox genes could be due to horizontal transfer, and coupled sulfate reduction/sulfide oxidation pathways, originating in planktonic ancestors of Chromatiaceae or Chlorobi, could be ancestral to all sulfur-lithotrophic processes. However, the possibility that chemolithotrophy, originating in deep sea, is the actual ancestral form of sulfur oxidation cannot be ruled out. [source] Not so old Archaea , the antiquity of biogeochemical processes in the archaeal domain of lifeGEOBIOLOGY, Issue 5 2009CARRINE E. BLANK Since the archaeal domain of life was first recognized, it has often been assumed that Archaea are ancient, and harbor primitive traits. In fact, the names of the major archaeal lineages reflect our assumptions regarding the antiquity of their traits. Ancestral state reconstruction and relaxed molecular clock analyses using newly articulated oxygen age constraints show that although the archaeal domain itself is old, tracing back to the Archean eon, many clades and traits within the domain are not ancient or primitive. Indeed many clades and traits, particularly in the Euryarchaeota, were inferred to be Neoproterozoic or Phanerozoic in age. Both Eury- and Crenarchaeota show increasing metabolic and physiological diversity through time. Early archaeal microbial communities were likely limited to sulfur reduction and hydrogenotrophic methanogenesis, and were confined to high-temperature geothermal environments. However, after the appearance of atmospheric oxygen, nodes containing a wide variety of traits (sulfate and thiosulfate reduction, sulfur oxidation, sulfide oxidation, aerobic respiration, nitrate reduction, mesophilic methanogenesis in sedimentary environments) appear, first in environments containing terrestrial Crenarchaeota in the Meso/Neoproterozoic followed by environments containing marine Euryarchaeota in the Neoproterozoic and Phanerozoic. This provides phylogenetic evidence for increasing complexity in the biogeochemical cycling of C, N, and S through geologic time, likely as a consequence of microbial evolution and the gradual oxygenation of various compartments within the biosphere. This work has implications not only for the large-scale evolution of microbial communities and biogeochemical processes, but also for the interpretation of microbial biosignatures in the ancient rock record. [source] Allylic Sulfones Containing Triene Moieties as Key Synthons for Carotenoid SynthesisHELVETICA CHIMICA ACTA, Issue 7 2003Minkoo Ji An efficient synthetic method for the allylic sulfone 2 containing a conjugated triene moiety has been proposed involving i) coupling of allylic sulfones 4 with the C5 bromoallylic sulfide 5, ii) base-promoted dehydrosulfonation in the presence of allylic sulfide, and iii) selective oxidation of the resulting trienyl sulfide to the corresponding sulfone. Total synthesis of lycopene starting from the C15 allylic sulfone 2b has been described, where the new C10 bis(chloroallylic) sulfone 11 proved to be a useful substitute for the C10 bis(chloroallylic) sulfide 3, which did not require the problematic chemoselective sulfur oxidation in a conjugated polyene. [source] The structure of the periplasmic thiol,disulfide oxidoreductase SoxS from Paracoccus pantotrophus indicates a triple Trx/Grx/DsbC functionality in chemotrophic sulfur oxidationACTA CRYSTALLOGRAPHICA SECTION D, Issue 3 2009Yvonne Carius The periplasmic thiol,disulfide oxidoreductase SoxS is beneficial for the sulfur-oxidizing (Sox) phenotype of the facultative chemotrophic bacterium Paracoccus pantotrophus and is not part of the Sox enzyme system. SoxS combines features of thioredoxins, glutaredoxins and the thiol,disulfide oxidoreductases of the Dsb family in structure, target specificity and reaction. The structure of SoxS was solved in oxidized and reduced forms at 2.1 and 1.9,Å resolution, respectively. SoxS revealed high structural homology to typical cytoplasmic bacterial thioredoxins. In contrast, SoxS contained the active-site motif Pro-Gly-Cys-Leu-Tyr-Cys that is not present in other thioredoxins. Interestingly, the sequence of this motif is closely related to the Pro-Gly-Cys-Pro-Tyr-Cys sequence of some glutaredoxins and to the Pro-Xaa-Cys-Xaa-Tyr-Cys sequences of some members of the DsbC and DsbG subfamilies of thiol,disulfide oxidoreductases. Furthermore, the proposed substrate of SoxS, the interprotein disulfide of SoxY, Cys110Y,Cys110Y, is structurally similar to oxidized glutathione. However, SoxS is proposed to specifically reduce the interprotein disulfide between two SoxY subunits, releasing a heterodimeric SoxYZ as an active part of the sulfur-oxidation cycle. [source] | ||||||||||