Subpicosecond characterization of the optical properties of the primary electron donor and the mechanism of the initial electron transfer in Rhodobacter capsulatus reaction centers

FEBS Letters

Holten, Dewey¹  Kirmaier, Christine¹ 

[1] Department of Chemistry, Washington University, St. Louis, MO 63130, USA

关键词: Reaction center;    Electron transfer;    Photosynthesis;    Femtosecond spectroscopy;   

DOI  :  10.1016/0014-5793(88)80919-0

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The optical difference spectrum of the excited primary electron donor, P*, in Rb. capsulatus reaction centers has been measured 600 fs after a 350-fs flash at 870 nm. The spectrum is characterized by bleaching in the ground state absorption bands at 855 and 600 nm, and a weak featureless transient absorption in between. The lack of significant (if any) bleaching at 800 nm indicates that P does not contribute appreciable oscillator strength to the 800-nm ground state absorption band. The conversion of P* to P⁺BPH⁻ _L is accompanied by isosbestic points in the transient difference spectra at 765 and 798 nm. The existence of the longer-wavelength isosbestic point, occurring essentially at the near-infrared absorbance maximum of the accessory BChls, provides compelling evidence that if state P*BChl⁻ _L forms, its transient concentration is exceedingly small. At certain wavelengths in the near-infrared the absorption changes develop somewhat more slowly than the rate at which P* decays, a finding that may reflect a contribution from readjustments in the pigment-protein complex in response to electron transfer.

【 授权许可】

Unknown