Probing the contribution of electronic coupling to the directionality of electron transfer in photosynthetic reaction centers

Article Abstract:

Subpicosecond transient absorption studies are reported for a set of Rhodobacter (R.) capsulatus bacterial photosynthesis reaction centers (RCs) designed to probe the origins of the unidirectionality of charge separation through one of two electron transport chains in the native pigment-protein complex. The result states an upper limit of V(sub L)(super 2)/V(sub M)(super 2) less than or equal to 4 for the contribution of the electronic coupling elements to the relative rates of electron transfer to the L versus M sides of the wild-type RC.

Photosynthesis research, Spin coupling

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Primary events in photosynthetic reaction centers with multiple mutations near the photoactive electron carriers

Article Abstract:

The primary charge separation reactions in two Rhodobacter capsulatus bacterial reaction canter (RC) mutants that have multiple mutations near the L-side bacteriochlorophyll [(BChl(sub L)] and bacteriopheophytin [(BPh(super L)] cofactors is investigated. The results obtained complement those on related mutants in providing a consistent picture of the free energies of the states and the primary events in this family of RCs and in the native system.

Polypeptides, Spectra, Microbial mutation, Structure

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B-side electron transfer to form P+H(sub B)(super -) in reaction centers from the F(L181)Y/Y (M208)F mutant of Rhodobacter capsulatus

Article Abstract:

The substitution of phenylalanine [Phe(L181)] by tyrosine(Tyr) and Tyr(M 208) by Phe amino acid in the reaction centers (RCs) of Rhodobacter capsulatus yields an RC with 15 percent yield of charge separation to the B-side bacteriophephytin (H(sub B)). The analysis is based on the relative bleaching of the quinone (Q(sub x)) bands of H(sub A) and H(sub B) at 542 and 527 nm, respectively.

Science & research, Research, Amino acids, Phenylalanine, Chemical properties

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