Electron superhighways and bridges in protein complexes

Does Natural Selection optimize biomachinery at the quantum level? Does quantum coherence play a role in biochemical electron transport? We show that a particular redox protein complex is configured so that metastable water bridges act as "superhighways" for coherent electron transport between its constituent protein molecules. The bridge enables fast coherent electron transport across the gap instead of dooming the electron to slow thermal hopping through the interprotein medium. Although our study focuses on a particular protein complex that has been frozen and characterized by crystallography, we conjecture that bridge-building is ubiquitous for redox processes.