Electron Hopping Through The 15 A Triple Tryptophan Molecular Wire In Dnarnphotolyase Occurs Within 30 Ps

摘要

Long-range electron transport plays a key role in many biochemical processes. Whereas the direct electron transfer (ET) between redox partners becomes too slow to be physiologically relevant at distances greater than ca. 14 A, efficient long-range transport can take place via hopping mechanisms involving intermediates. Examples include ET through, effectively "one-dimensional", DNA and peptide chains. In proteins, multistep ET also takes place in many processes through well-defined intermediates defining a path through the three-dimensional structure. For instance, the presence of a single Trp residue between a Cu center and a chemically attached photoreducible dye in azurin was shown to speed up long-range ET by 2 orders of magnitude to the nanosecond regime. In some cases a range of identical redox-active components bridges the ultimate donor and acceptor. The best-studied example of this case is the triple tryptophan (Trp) chain in DNA photolyase (PL). Here, electron transport from a solvent-exposed Trp to a flavin radical (FADH) located on the other side of the protein is mediated by two intermediate Trp residues.