title: Tryptophan-accelerated electron flow through proteins.
abstract: Energy flow in biological structures often requires submillisecond charge transport over long molecular distances. Kinetics modeling suggests that charge-transfer rates can be greatly enhanced by multistep electron tunneling in which redox-active amino acid side chains act as intermediate donors or acceptors. We report transient optical and infrared spectroscopic experiments that quantify the extent to which an intervening tryptophan residue can facilitate electron transfer between distant metal redox centers in a mutant Pseudomonas aeruginosa azurin. Cu(I) oxidation by a photoexcited Re(I)-diimine at position 124 on a histidine(124)-glycine(123)-tryptophan(122)-methionine(121) beta strand occurs in a few nanoseconds, fully two orders of magnitude faster than documented for single-step electron tunneling at a 19 angstrom donor-acceptor distance.
authors.affiliation: Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Crystal
authors.initials: C
authors.lastname: Shih
authors.forename: Anna Katrine
authors.initials: AK
authors.lastname: Museth
authors.forename: Malin
authors.initials: M
authors.lastname: Abrahamsson
authors.forename: Ana Maria
authors.initials: AM
authors.lastname: Blanco-Rodriguez
authors.forename: Angel J
authors.initials: AJ
authors.lastname: Di Bilio
authors.forename: Jawahar
authors.initials: J
authors.lastname: Sudhamsu
authors.forename: Brian R
authors.initials: BR
authors.lastname: Crane
authors.forename: Kate L
authors.initials: KL
authors.lastname: Ronayne
authors.forename: Mike
authors.initials: M
authors.lastname: Towrie
authors.forename: Antonín
authors.initials: A
authors.lastname: Vlcek
authors.forename: John H
authors.initials: JH
authors.lastname: Richards
authors.forename: Jay R
authors.initials: JR
authors.lastname: Winkler
authors.forename: Harry B
authors.initials: HB
authors.lastname: Gray
mesh_terms: D001400:Azurin / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004583:Electrons; D004735:Energy Transfer; D007700:Kinetics; D008024:Ligands; D008956:Models, Chemical; D050505:Mutant Proteins / Q000737:chemistry; D010084:Oxidation-Reduction; D010649:Phenylalanine / Q000737:chemistry; D011550:Pseudomonas aeruginosa / Q000737:chemistry; D012211:Rhenium / Q000737:chemistry; D013057:Spectrum Analysis; D013816:Thermodynamics; D014364:Tryptophan / Q000737:chemistry*; D014443:Tyrosine / Q000737:chemistry
chemical_list: D008024:Ligands; D050505:Mutant Proteins; D001400:Azurin; D014443:Tyrosine; D010649:Phenylalanine; D012211:Rhenium; D003300:Copper; D014364:Tryptophan