Electron transfer in pheophytin a‐modified reaction centers from Rhodobacter sphaeroides (R‐26)
- 10 May 1993
- journal article
- Published by Wiley in FEBS Letters
- Vol. 322 (2) , 168-172
- https://doi.org/10.1016/0014-5793(93)81561-d
Abstract
The major part (> 90%) of bacteriopheophytin a in reaction centers (RCs) of Rhodobacter sphaeroides was substituted by plant pheophytin a. In modified RCs the photochemical formation of P+Qa − occurs with with a quantum efficiency of 79%. The intermediary state P+I− displayed a recombination time constant of 1.5 ns, and the electron transfer from I− to Qa was characterized by a time constant of 540 ps. On the basis of spectral properties of P+I− for native and modified RCs, it was suggested that bacteriopheophytin, as well as bacteriochlorophyll monomers located in L protein branch, have a transition at 545 nm with approx. equal extinction coefficients. Accordingly, the state P+I− in modified RCs is proposed to consist of a thermodynamic mixture of P+BL− (∼ 80%) and P+Phe− (∼ 20%).Keywords
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