ABSTRACT
In nature, proteins serve as media 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 stabilise the Phe radical cation. This neighbouring-amide-group effect helps improve understanding of the mechanism of extracellular electron transfer through conductive protein filaments (pili) of anaerobic bacteria during mineral respiration.
Subject(s)
Amides/chemistry , Peptides/chemistry , Phenylalanine/chemistry , Electron Transport , Electrons , Kinetics , Models, Molecular , ThermodynamicsABSTRACT
Nature uses peptide aggregates as soft materials for electron transfer over long distances. These reactions occur in a multistep hopping reaction with various functional groups as relay stations that are located in the side chain and in the backbone of the peptides.
Subject(s)
Peptides/chemistry , Amino Acids/chemistry , Electron TransportABSTRACT
Electron transfer (ET) processes in proteins drive the energy conversion processes in cells and are also involved in metabolic catalysis. In this tutorial review, the models explaining ET through peptides and proteins are discussed and the biological relevance of ET is elucidated.
Subject(s)
Peptides/metabolism , Proteins/metabolism , Cell Respiration , Electron Transport , Free Radicals/chemistry , Free Radicals/metabolism , Peptides/chemistry , Photosynthesis , Proteins/chemistryABSTRACT
Proteins and peptides use their amino acids as medium for electron-transfer reactions that occur either in single-step superexchange or in multistep hopping processes. Whereas the rate of the single-step electron transfer dramatically decreases with the distance, a hopping process is less distance dependent. Electron hopping is possible if amino acids carry oxidizable side chains, like the phenol group in tyrosine. These side chains become intermediate charge carriers. Because of the weak distance dependency of hopping processes, fast electron transfer over very long distances occurs in multistep reactions, as in the enzyme ribonucleotide reductase.
