Mn4Ca Cluster in Photosynthesis: Where and How Water is Oxidized to Dioxygen

摘要: Oxygen, which supports all aerobic life, is produced by photosynthetic water oxidation in plants, algae, and cyanobacteria. The water-oxidation reaction probably first appeared nature ∼3 billion years ago the precursors to present-day cyanobacteria, although exact timing not yet entirely clear.1−5 A key component appearance of oxygenic photosynthesis was a metal complex that could store oxidizing equivalents facilitate four-electron two molecules dioxygen, meanwhile making electrons available for reductive carbon-fixing reactions required sustaining life.6−8 This involved photosynthesis, oxygen-evolving (OEC), consists an oxo-bridged structure with four Mn atoms one Ca atom. No variations have been observed so far among organisms through higher plants algae back represents earliest organisms. Oxygen itself byproduct shown eq 1: 1 However, it this oxygen enabled life evolve led current diverse on earth dramatically increasing metabolic energy became from respiration. process also development protective ozone layer, allowed transition marine forms terrestrial life.