Model for primary charge separation in reaction centers of photosynthetic bacteria.

We present model calculations of the dynamics of primary electron transfer (ET) in reaction centers of photosynthetic bacteria. We obtain half times of [unk]1 ps and approximately 5 ps for the first two ET processes, in excellent agreement with experimental observations. Our model is based on (i) a theoretical framework capable of describing ET in the presence of strong electronic interstate resonance coupling and (ii) energy parameters extracted from recent experimental data and molecular orbital calculations. Our analysis suggests that (i) strong electronic interstate mixing is crucial to the rapidity and efficiency of irreversible ET; (ii) possibly five rather than three electronic states participate in the transient ET prior to the reduction in vivo of the quinone complex; and (iii) conventional ET theories, which rely on weak electronic interstate mixing, are unfit for describing ET in reaction centers of photosynthetic bacteria.