Interfacial electron transfer (ET) between outer-membrane cytochromes and soluble electron acceptors is thought to be a key step in microbial metal reduction by dissimilatory metal-reducing bacteria. In our study, we use computational molecular modeling to predict rates for these reactions from first principles. So far, we have calculated the electronic coupling energy, VRP, and the ET rate constant, kET, of an inner-sphere ET complex consisting of a lone imidazole-ligated heme cofactor (electron donor) and an Fe(III)-EDTA molecule (electron acceptor) using the methods established by Smith et al. (2006) and Kerisit et al. (2007). Our calculated VRP = 1.20 kJ/mol is consistent with nonadiabatic ET and in good agreement with previous values based on our Fe-Fe distance of 8.1 �. Our calculated kET = 3.3�105 s-1 compares well with our observed kET = 3.8�105 s-1. Currently, we are adapting these calculations to an inner-sphere ET complex consisting of a lone imidazole-ligated heme cofactor (electron donor) and a flavin mononucleotide molecule (electron acceptor), towards a comprehensive picture of direct versus indirect (via electron shuttles) interfacial biomolecular ET.

Computational molecular modeling of microbial iron reduction

242nd National Meeting (2011)

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