Electron Transfer in Peptides with Cysteine and Methionine as Relay Amino Acids

摘要

Recently, we developed a peptide system 1 which allows the detection of a multistep hopping process in electron-transfer (ET) reactions through peptides. As the rate for a single-step ET reaction between an electron donor (D) and an electron acceptor (A) decreases exponentially with the distance, long-range ET is fast only if a multistep hopping process occurs. According to this mechanism, the overall distance between D and A is split into shorter and, therefore, faster ET steps. Relay amino acids act as stepping stones for these multistep reactions by acting as intermediate charge carriers. Until now, only aromatic amino acids such as tyrosine and tryptophan have been discussed as relay amino acids. We now show that the aliphatic amino acids cysteine and methionine can also function as relay amino acids in ET through peptides.