Coherent dynamics during the primary electron-transfer reaction in membrane-bound reaction centers of Rhodobacter sphaeroides.
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.
Vos
M H
MH
Laboratoire d'Optique Appliquée, Ecole Polytechnique-ENSTA, INSERM U275, CNRS URA 1406, France.
Jones
M R
MR
Hunter
C N
CN
Breton
J
J
Lambry
J C
JC
Martin
J L
JL
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
D045322:Photosynthetic Reaction Center Complex Proteins