Sequential electron transfer relay

Photophysical studies allow the measurement of rate constants for transmembrane electron transfer. The distributed kinetics observed in describing the decay of photovoltage across a BLM is consistent with a highly inhomogeneous disposition of donors and relays within the membrane [111, 112]. A typical value for the rate constant for electron transfer across a BLM (about 10 sec-1) would predict a spatial separation of about 10 A, whereas the thickness of the bilayer is usually about 40-50 A. This apparent discrepancy can be resolved if transmembrane electron transfer occurs by several sequential steps involving deeply buried redox sites, thus decreasing the operational tunnelling distance [113]. 

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