Transient absorption spectroscopy with a time resolution of similar to 1 ns was applied to study the decay of the primary radical pair P+H- in Rhodobacter sphaeroides R-26 reaction centers with blocked electron transfer from H- to Q(A). The block in the electron transfer was realized in two ways: by either reducing or removing Q(A). We found very different kinetics of the P+H- decay in these two cases. Convolution of the multiexponential decay with the instrument response function allowed resolution of as many as three kinetic components of < 1-, 3-4-, and 9-12-ns lifetimes in chromatophores with Q(A) reduced and in isolated reaction centers both with Q(A) either reduced or removed (with or without o-phenanthroline) but with variable relative amplitudes. Removing Q(A) or adding o-phenanthroline to isolated reaction centers increased the amplitude of the slowest decay phase relative to that of the fastest phase. On the basis of these observations, we propose that reaction centers adopt three conformational states characterized by different decay kinetics of P+H-. These conformational states appear to be controlled by the charges in the vicinity of the Q(A) site as revealed by the effects of Q(A) reduction and o-phenanthroline-mediated protonation of the sites close to Q(A).