The Oxo-Gate Hypothesis and DMSO Reductase: Implications for a Psuedo-σ Bonding Interaction Involved in Enzymatic Electron Transfer

Abstract

The electronic structure of (PPh4)[MoO(benzene-1,2-dithiolate)2], a paramagnetic analogue of the oxidized active site of DMSO reductase, has been investigated by electronic absorption, magnetic circular dichroism, and resonance Raman spectroscopies. A pseudo-σ bonding interaction exists between the Mo dxy redox orbital and in-plane dithiolate orbitals, and this is the origin of the two lowest energy charge transfer features. The similar low-energy spectral features of the model and enzyme imply similar coordination geometries and suggest that a σ-mediated electron transfer process is operative.