Excitation trapping and primary charge stabilization in Rhodopseudomonas viridis cells, measured electrically with picosecond resolution

AUTOR(ES)

Deprez, J.

RESUMO

The transmembrane primary charge separation in the photosynthetic bacterium Rhodopseudomonas viridis was monitored by electric measurements of the light-gradient type [Trissl, H. W. & Kunze, U. (1985) Biochim. Biophys. Acta 806, 136-144]. Excitation of whole cells with 30-ps laser pulses at either 532 nm or 1064 nm gave rise to a biphasic increase of the photovoltage. The fast phase, contributing about 50% of the total, rose with an exponential time constant ≤40 ps and was independent of the redox state of the quinone electron acceptor. It is assigned to the migration of the excitation energy in the antenna and its subsequent trapping by the reaction center, monitored by the ultrafast charge separation between the primary electron donor and the bacteriopheophytin intermediary acceptor. The slower phase (125 ± 50 ps) only occurred when the quinone was oxidized and disappeared when it was reduced (either chemically or photochemically). It is assigned to the forward electron transfer from the bacteriopheophytin to the quinone. The relative amplitudes of these two electrogenic steps demonstrate that the bacteriopheophytin intermediary acceptor is located halfway between the primary donor and the quinone.

Documentos Relacionados

• Femtosecond spectroscopy of excitation energy transfer and initial charge separation in the reaction center of the photosynthetic bacterium Rhodopseudomonas viridis
• Micromotion of mammalian cells measured electrically
• Micromotion of mammalian cells measured electrically.
• Nanodissection and high-resolution imaging of the Rhodopseudomonas viridis photosynthetic core complex in native membranes by AFM
• Efficient exchange of the primary quinone acceptor QA in isolated reaction centers of Rhodopseudomonas viridis