High and low resolution theories of protein electron transfer

Abstract

Protein-mediated electronic interactions facilitate biological electron transfer (ET) reactions. Theory and experiment are being used extensively to establish atomic-scale descriptions of these reactions. The last 20 years have seen a progression of descriptions ranging from square barrier protein approximations to tunneling Pathway models, and recently to valence orbital Hamiltonian methods. Pathway connectivity, reflecting a protein's secondary and tertiary motif, is predicted (and was recently confirmed) to determine the ET rate. A critical challenge now is to extract from more detailed orbital descriptions, with millions of interaction elements between orbitals, predictions of how primary sequence and folding-induced contacts influence electron transfer rates. Electron transfer contact maps reduce the orbital interaction information in a manner that allows ready interpretation in the context of protein motifs and mutations. We discuss these modern models for protein ET and the reduced views that are being derived from them.