title: [Light-dependent paramagnetic center in photosystem 2 of higher plants].
abstract: In subchloroplast fragments of photosystem II from Vicia faba, free from P700 contamination, a free-radical ESR signal (singlet of 9 G peak-to-peak line-width, g approximately 2,0025) appears under illumination in presence of silicomolybdate as electron acceptor. Using ESR-active electron donors and acceptors as well as conventional redox reagents Hill activity of preparations has been evaluated under different conditions. Evidences are presented that the light-induced dark-reversible silicomolybdate-dependent ESR signal is of the same origin as photobleaching centered at 680 nm which has been earlier interpreted as a result of P680 center of photosystem II oxydation. The relaxation properties of this paramagnetic center as measured by microwave power saturation are different from that of P700+-center in photosystem I.
mesh_terms: D001665:Binding Sites; D002736:Chloroplasts / Q000528:radiation effects*; D004578:Electron Spin Resonance Spectroscopy; D008027:Light; D008982:Molybdenum; D010084:Oxidation-Reduction; D010788:Photosynthesis; D012825:Silicon; D013057:Spectrum Analysis; D013696:Temperature
chemical_list: D008982:Molybdenum; D012825:Silicon
vernacular_title: Svetozavisimyĭ paramagnitnyĭ tsentr v fotosisteme 2 vysshikh rasteniĭ.