Development of Fluorinated Mechanistic Probes towards Studies of the Controlled Oxidation of Aliphatics by Metalloenzymes
To initiate the C-H bond oxidation of the aliphatic compounds is a great challenge for synthetic chemists. The conventional synthetic methods and industrial processes are usually required with extremely high temperature and high pressure to carry out the corresponding events. However, some of the gram-negative bacteria, like methanotropic bacteria, Pseudomonas spp. and Bacillus megaterium can facilely convert aliphatic fine chemicals to the corresponding alcohols or oxiranes at ambient temperature and pressure.
gem-Difluoromethylene substituted molecules constitute a distinct class of fluorinated compounds and a special chemistry developed for their preparation. The terminal hydroxylation of these gem-difluorinated octanes by AlkB (Alkane Hydroxylase) from Pseudomonas putida Gpo1 is highly selective for the formation of gem-difluorinated octan-1-ols. The hydroxylation reaction could be performed under conditions of whole-cell catalysis.
Tunning the Reactivity of Metalloproteins for Regio- and Stereoselective Activation of Aliphatics
We employed the water-soluble cytochrome P450 BM-3 to study the activity and regiospecificity of the oxidation on fluorinated n-octanes. By facilitating with appropriate mutations, these variants could regio-selectively convert fluorinated C8 alkanes to their corresponding secondary alcohols. The pattern of reactivity, especially an unprecedented regio-selectivity and stereoselectivity observed for 4,4-difluorooctane, suggests that specific interactions of the fluorinated substituent with aromatic p-systems within the active site can tune the binding of the substrate to the binding pocket as well as the protein conformational states and protein dynamics that participate in electron transfer and C-H activation.
Unraveling the Metal Core Structures of Transcriptional Factors Containing Iron-Sulfur Clusters for their Redox Regulation in Prokaryote
SoxR, a transcriptional factor, is a homodimeric protein with each subunit containing a redox-active [2Fe-2S] center. The iron–sulfur clusters within SoxR regulate transcriptional activity in response to one-electron oxidation, from the paramagnetic mixed-valence [FeII-FeIII] to the diamagnetic [FeIII-FeIII] species; a process that is presumably mediated by oxidative stress. The corresponding oxidation could trigger the expression of the soxS gene and subsequently activate numerous defensive genes, such as superoxide dismutase or catalase in Escherichia coli.
Series of spectroscopic studies of the reduced and oxidized forms of the Escherichia coli transcriptional factor SoxR, followed by mechanistic analyses of the nitrosylation process of these species, allowed the elucidation of the redox chemistry associated with NO sensing that triggers transcriptional activation for the sensing of small molecules in a prokaryote.