Protons Coming and Going

摘要

Photosynthesis channels light into chemical energy by splitting water. Klauss et al. explored the sequence of steps whereby the manganese cluster in plants and algae extracts four protons and four electrons from two water molecules, forming O_2 in the process. By applying a photothermal beam deflection technique to probe the relative timing of electron and proton transfers, the authors uncovered two deprot-onation steps, which taken together with prior studies establish that the water-splitting cycle proceeds through strictly alternating extraction of electrons and protons.