Initial electron transfer in photosynthetic reaction centers of Rhodobacter capsulatus mutants

Abstract The stimulated emission decay time constants were measured for a series of Rhodobacter capsulatus reaction centers with site-specific mutations at the symmetry related locations M208 and L181. We report the first mutant (Phe L181 → Tyr) that exhibits an initial electron transfer rate faster than the native organism at 295 K, and determine that the tyrosine at position M208 cannot be fully responsible for the unidirectionality of electron transfer.