Femtosecond spectroscopy of excitation energy transfer and initial charge separation in the reaction center of the photosynthetic bacterium Rhodopseudomonas viridis

AUTOR(ES)

Breton, J.

RESUMO

Reaction centers from the photosynthetic bacterium Rhodopseudomonas viridis have been excited within the near-infrared absorption bands of the dimeric primary donor (P), of the “accessory” bacteriochlorophylls (B), and of the bacteriopheophytins (H) by using laser pulses of 150-fsec duration. The transfer of excitation energy between H, B, and P occurs in slightly less than 100 fsec and leads to the ultrafast formation of an excited state of P. This state is characterized by a broad absorption spectrum and exhibits stimulated emission. It decays in 2.8 ± 0.2 psec with the simultaneous oxidation of the primary donor and reduction of the bacteriopheophytin acceptor, which have been monitored at 545, 675, 815, 830, and 1310 nm. Although a transient bleaching relaxing in 400 ± 100 fsec is specifically observed upon excitation and observation in the 830-nm absorption band, we have found no indication that an accessory bacteriochlorophyll is involved as a resolvable intermediary acceptor in the primary electron transfer process.

Documentos Relacionados

• Calculated coupling of electron and proton transfer in the photosynthetic reaction center of Rhodopseudomonas viridis.
• Microaerophilic growth and induction of the photosynthetic reaction center in Rhodopseudomonas viridis.
• Nobel lecture. The photosynthetic reaction centre from the purple bacterium Rhodopseudomonas viridis.
• Mechanism of the initial charge separation in bacterial photosynthetic reaction centers.
• A system for site-specific mutagenesis of the photosynthetic reaction center in Rhodopseudomonas viridis.