title: Coherent dynamics during the primary electron-transfer reaction in membrane-bound reaction centers of Rhodobacter sphaeroides.
abstract: The temporal evolution of the near-infrared stimulated emission band of the special pair excited state (P*) in the reaction center of Rhodobacter sphaeroides has been studied in intracytoplasmic membranes of the antenna-deficient RCO1 mutant at 10 K with a resolution of 30 fs. On the 100-fs time scale the emission band gradually shifts to longer wavelengths. After 150 fs the band shifts back to shorter wavelengths and continues to develop on the picosecond time scale in a damped oscillatory manner (most prominent fundamental frequencies around 15 cm-1 and at 92, 122, and 153 cm-1). These phenomena are shown to be due to low-frequency vibrational motions in the P* excited state that conserve their phase on the time scale of electron transfer. These results imply that the vibrational manifold of P* is not thermalized during the electron-transfer reaction in functional reaction centers. The initial Stokes shift dynamics are largely determined by the modes in the 90-160-cm-1 frequency range, which probably involve motions of several chromophores, including the bacteriopheophytin electron acceptor HL.
authors.affiliation: Laboratoire d'Optique Appliquée, Ecole Polytechnique-ENSTA, INSERM U275, CNRS URA 1406, France.
authors.forename: M H
authors.initials: MH
authors.lastname: Vos
authors.forename: M R
authors.initials: MR
authors.lastname: Jones
authors.forename: C N
authors.initials: CN
authors.lastname: Hunter
authors.forename: J
authors.initials: J
authors.lastname: Breton
authors.forename: J C
authors.initials: JC
authors.lastname: Lambry
authors.forename: J L
authors.initials: JL
authors.lastname: Martin
mesh_terms: D004579:Electron Transport; D007700:Kinetics; D009154:Mutation; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics / Q000378:metabolism*; D012242:Rhodobacter sphaeroides / Q000235:genetics / Q000378:metabolism*; D013055:Spectrophotometry, Infrared
chemical_list: D045322:Photosynthetic Reaction Center Complex Proteins