{'fraction_non_alphanumeric': 0.025307302964569775, 'fraction_numerical': 0.018799710773680405, 'mean_word_length': 5.653846153846154, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Excited states, electron-transfer reactions, and intermediates in bacterial photosynthetic reaction centers

The three-dimensional structure of a photosynthetic reaction center has recently been obtained at atomic resolution using x-ray crystallography by Deisenhofer, Epp, Miki, Huber, and Michel (J. Mol. Biol. 1984, 180, 385-398; Nature 1985, 318, 618-624). This breakthrough provides the fundamental structural information needed to understand the mechanisms of the initial energy- and electron-transfer steps in photosynthesis. The structure reveals the distances among the reactive bacteriochlorophylls and quinones as well as the location of all nearby solvent molecules, the amino acids of the reaction center protein. Thus, the reaction center provides a complex but well-defined solid-state reactive system for the study of fundamental physical and chemical processes with implications and applications well beyond this specific system. We review recent studies of the reaction intermediates and mechanism of electron transfer in which the energetics and reaction dynamics have been perturbed with external electric and magnetic fields. Electron-transfer mechanisms which have been proposed are reviewed critically in light of the available data, and electron transfer in the reaction center is compared with electron transfer in other biological and nonbiological systems.