B-Side Electron Transfer To Form P+HB- in Reaction Centers from the F(L181)Y/Y(M208)F Mutant of Rhodobacter capsulatus

The combination of the Phe(L181) → Tyr and Tyr(M208) → Phe amino acid substitutions in reaction centers (RCs) of Rhodobacter capsulatus yields an RC in which charge separation to the B-side bacteriopheophytin (H B ) occurs in about 15% yield. This yield is determined from analysis of the relative bleachings of the Q X bands of H A and H B at 542 and 527 nm, respectively, and comparison to simulations. These results are presented along with comparison to previous work on this “YF” mutant and other mutant RCs that produce electron transfer to the B-side of the RC.