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Electron transfer in pheophytin a ‐modified reaction centers from Rhodobacter sphaeroides (R‐26)
Author(s) -
Shkuropatov A.Ya.,
Shuvalov V.A.
Publication year - 1993
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(93)81561-d
Subject(s) - rhodobacter sphaeroides , pheophytin , bacteriochlorophyll , chemistry , photosynthetic reaction centre , electron transfer , photochemistry , recombination , reaction rate constant , monomer , photosynthesis , kinetics , photosystem ii , physics , biochemistry , quantum mechanics , organic chemistry , gene , polymer
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 + Q a − 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 Q a 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%).