Electron Flow through Metalloproteins

Electron flow through proteins and protein assemblies in the and respiratory machinery commonly occurs metal centers or other redox cofactors that are by relatively large molecular distances, often in the 10−20 Å range. To inorganic chemists, such long-distance transfer was a mystery for many years, as we were to close-contact models for the transition states of self-exchange reactions between metal ions in aqueous. One of our favorite reactions was the ferrous/ferric -exchange, which had been investigated thoroughly by (Dick) Dodson at the Brookhaven National Laboratory the 1940s (and published in Journal of the American Chemical in 1950). Dodson showed that the half-time for this was on the order of seconds, which he noted was “fast” in today’s femtosecond world is very “slow”. Indeed, this simple electron transfer, where no bonds are formed or, was found to be orders of magnitude slower than long-distance electron flow through metalloprotein molecules. How could this be?