Influence of Cofactor Regeneration Strategies on Preparative-Scale, Asymmetric Carbonyl Reductions by Engineered Escherichia coli

This study was designed to determine whether whole cells or crude enzyme extracts are more effective for preparative-scale ketone reductions by dehydrogenases as well as learning which cofactor regeneration scheme is most effective. Based on results from three representative ketone substrates (an α-fluoro-β-keto ester, a <i>bis</i>-trifluoromethylated acetophenone, and a symmetrical β-diketone), our results demonstrate that several nicotinamide cofactor regeneration strategies can be applied to preparative-scale dehydrogenase-catalyzed reactions successfully

Photophysics and Light-Activated Biocidal Activity of Visible-Light-Absorbing Conjugated Oligomers

The photophysical properties of three cationic π-conjugated oligomers were correlated with their visible light activated biocidal activity vs <i>S. aureus</i>. The oligomers contain three arylene units (terthiophene, <b>4a</b>; thiophene-benzotriazole-thiophene, <b>4b</b>; thiophene-benzothiadiazole-thiophene, <b>4c</b>) capped on each end by cationic −(CH₂)₃NMe₃⁺ groups. The oligomers absorb in the visible region due to their donor–acceptor–donor electronic structure. Oligomers <b>4a</b> and <b>4b</b> have high intersystem crossing and singlet oxygen sensitization efficiency, but <b>4c</b> has a very low intersystem crossing efficiency and it does not sensitize singlet oxygen. The biocidal activity of the oligomers under visible light varies in the order <b>4a</b> > <b>4b</b> ≈ <b>4c</b>