Nature uses proteins as medium for long‐distance electron transfer (ET) to carry out redox reactions in distant compartments. This ET occurs either by a single‐step superexchange or through a multi‐step charge hopping process, which uses side chains of amino acids as stepping stones. In this study we demonstrate that Phe can act as a relay amino acid for long‐distance electron hole transfer through peptides. The considerably increased susceptibility of the aromatic ring to oxidation is caused by the lone pairs of neighbouring amide carbonyl groups, which stabilize the Phe radical cation. This neighbouring amide group effect helps to better understand the mechanism of extracellular electron transfer through conductive protein filaments (pili) of anaerobic bacteria during mineral respiration.
U. Wille, J. Nathanael, L. Gamon, M. Cordes, Paul R. Rablen, T. Bally, K. Fromm, and B. Giese.
"Amide Neighbouring Group Effects In Peptides: Phenylalanine As Relay Amino Acid In Long‐Distance Electron Transfer".