The 2004 Benjamin Franklin Medal in Chemistry presented to Harry B. Gray

The Franklin Institute, Philadelphia, Pennsylvania, awarded the 2004 Benjamin Franklin Medal in Chemistry to Harry B. Gray for his pioneering contributions in the field of electron transfer in metalloproteins. In a series of elegant and challenging experiments beginning in the late 70s, Gray and his coworkers have shown that the transfer of electrons in metalloproteins can proceed over long distances (~ 20 Å) and at fast rates. These experiments have involved the regiospecific functionalization of structurally characterized electron transfer proteins with ruthenium complexes, coupled with laser excitation and transient spectroscopy. Probing the effects of thermodynamic driving force, temperature, donor-acceptor distance and electronic coupling, Gray has shaped our detailed current understanding of the principles governing biological electron flow. The mechanism of electron transfer has been identified as electron tunneling mediated by the molecules separating donor and acceptor. Tunneling timetables have been established for various intervening media. Important biological processes like respiration and photosynthesis depend on facile electron transfer, and Gray's contribution serves as the fundamental basis for understanding these and many related reactions.