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Enzymatic Reduction (enzymatic + reduction)
Selected AbstractsChemInform Abstract: Asymmetric Synthesis of Both Antipodes of ,-Hydroxy Nitriles and ,-Hydroxy Carboxylic Acids via Enzymatic Reduction or Sequential Reduction/Hydrolysis.CHEMINFORM, Issue 26 2009Haribabu Ankati 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 of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Dynamic Kinetic Resolution of tert-Butyl 4-Methyl-3,5-dioxohexanoate Through Enzymatic Reduction.CHEMINFORM, Issue 16 2001Aiguo Ji Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Enantioselective Enzymatic Reductions of Sterically Bulky Aryl Alkyl Ketones Catalyzed by a NADPH-Dependent Carbonyl Reductase.CHEMINFORM, Issue 16 2007Dunming Zhu 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] The Fe-only nitrogenase and the Mo nitrogenase from Rhodobacter capsulatusFEBS JOURNAL, Issue 6 2002A comparative study on the redox properties of the metal clusters present in the dinitrogenase components The dinitrogenase component proteins of the conventional Mo nitrogenase (MoFe protein) and of the alternative Fe-only nitrogenase (FeFe protein) were both isolated and purified from Rhodobacter capsulatus, redox-titrated according to the same procedures and subjected to an EPR spectroscopic comparison. In the course of an oxidative titration of the MoFe protein (Rc1Mo) three significant S = 1/2 EPR signals deriving from oxidized states of the P-cluster were detected: (1) a rhombic signal (g = 2.07, 1.96 and 1.83), which showed a bell-shaped redox curve with midpoint potentials (Em) of ,195 mV (appearance) and ,30 mV (disappearance), (2) an axial signal (g|| = 2.00, g, = 1.90) with almost identical redox properties and (3) a second rhombic signal (g = 2.03, 2.00, 1.90) at higher redox potentials (> 100 mV). While the ,low-potential' rhombic signal and the axial signal have been both attributed to the one-electron-oxidized P-cluster (P1+) present in two conformationally different proteins, the ,high-potential' rhombic signal has been suggested rather to derive from the P3+ state. Upon oxidation, the FeFe protein (Rc1Fe) exibited three significant S = 1/2 EPR signals as well. However, the Rc1Fe signals strongly deviated from the MoFe protein signals, suggesting that they cannot simply be assigned to different P-cluster states. (a) The most prominent feature is an unusually broad signal at g = 2.27 and 2.06, which proved to be fully reversible and to correlate with catalytic activity. The cluster giving rise to this signal appears to be involved in the transfer of two electrons. The midpoint potentials determined were: ,80 mV (appearance) and 70 mV (disappearance). (b) Under weakly acidic conditions (pH 6.4) a slightly altered EPR signal occurred. It was characterized by a shift of the g values to 2.22 and 2.05 and by the appearance of an additional negative absorption-shaped peak at g = 1.86. (c) A very narrow rhombic EPR signal at g = 2.00, 1.98 and 1.96 appeared at positive redox potentials (Em = 80 mV, intensity maximum at 160 mV). Another novel S = 1/2 signal at g = 1.96, 1.92 and 1.77 was observed on further, enzymatic reduction of the dithionite-reduced state of Rc1Fe with the dinitrogenase reductase component (Rc2Fe) of the same enzyme system (turnover conditions in the presence of N2 and ATP). When the Rc1Mo protein was treated analogously, neither this ,turnover signal' nor any other S = 1/2 signal were detectable. All Rc1Fe -specific EPR signals detected are discussed and tentatively assigned with special consideration of the reference spectra obtained from Rc1Mo preparations. [source] Isotopologue fractionation during N2O production by fungal denitrificationRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2008Robin L. Sutka Identifying the importance of fungi to nitrous oxide (N2O) production requires a non-intrusive method for differentiating between fungal and bacterial N2O production such as natural abundance stable isotopes. We compare the isotopologue composition of N2O produced during nitrite reduction by the fungal denitrifiers Fusarium oxysporum and Cylindrocarpon tonkinense with published data for N2O production during bacterial nitrification and denitrification. The fractionation factors for bulk nitrogen isotope values for fungal denitrification were in the range ,74.7 to ,6.6,. There was an inverse relationship between the absolute value of the fractionation factors and the reaction rate constant. We interpret this in terms of variation in the relative importance of the rate constants for diffusion and enzymatic reduction in controlling the net isotope effect for N2O production during fungal denitrification. Over the course of nitrite reduction, the ,18O values for N2O remained constant and did not exhibit a relationship with the concentration characteristic of an isotope effect. This probably reflects isotopic exchange with water. Similar to the ,18O data, the site preference (SP; the difference in ,15N between the central and outer N atoms in N2O) was unrelated to concentration during nitrite reduction and, therefore, has the potential to act as a conservative tracer of production from fungal denitrification. The SP values of N2O produced by F. oxysporum and C. tonkinense were 37.1,±,2.5, and 36.9,±,2.8,, respectively. These SP values are similar to those obtained in pure culture studies of bacterial nitrification but quite distinct from SP values for bacterial denitrification. The large magnitude of the bulk nitrogen isotope fractionation and the ,18O values associated with fungal denitrification are distinct from bacterial production pathways; thus multiple isotopologue data holds much promise for resolving bacterial and fungal production. Our work further provides insight into the role that fungal and bacterial nitric oxide reductases have in determining site preference during N2O production. Copyright © 2008 John Wiley & Sons, Ltd. [source] Enantio- and Diastereoselective Chemoenzymatic Synthesis of C2-Symmetric Biaryl-Containing DiolsCHEMCATCHEM, Issue 1 2010Edyta Burda Abstract An enantio- and diastereoselective synthesis of C2-symmetric diols bearing a biphenyl-framework has been developed by means of an enzymatic reduction of the corresponding diketones, which were prepared by a Suzuki coupling reaction. Furthermore, a chemoenzymatic one-pot synthesis of a C2-symmetric diol in aqueous media has been realized through combination of the Suzuki coupling reaction and enzymatic reduction. Chiral stereoisomers of the biaryl-containing diols are prepared with diastereomeric ratios in excess of 25:1 and enantiomeric excesses of greater than 99,%. [source] | ||||||||||