Title:  Electron Transfer Pathways In Biology

Abstract: Energy capture, storage, and conversion in living systems relies, fundamentally, on the flow of electrons and protons. The transport of electrons through proteins uses cofactors, special chemical groups that sequester electrons as they hop among these sites through otherwise insulating proteins. These cofactors trade electrons with one another via electron tunneling. Electrons thus move across membranes, generating a proton gradient, and leading to the synthesis of energy storing chemical bonds. Electron transfer reactions also participate in essential reaction of biosynthesis, damage repair, and signaling. Electrons flow in biology on time scales from picoseconds to seconds, and the trick for ensuring that the electrons get to the right places at the right times is to employ electron tunneling pathways between the charge localizing cofactors. I will describe the theoretical framework of how proteins control these reactions with tunneling pathways, and will discuss research frontiers that have become accessible to theoretical analysis as a consequence of the tunneling pathways framework. Examples will include the repair of DNA damage, the micrometer length scale flow of electrons through extracellular bacterial appendages, and electron bifurcation – a reaction that couples electron flow between two-electron donors and one-electron carriers.  The seminar will also present a historical perspective on the development of this field over the last 40 years.