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Updated: Oct 9, 2026

A New Approach for the Comparative Analysis of Multiprotein Complexes Based on 15N Metabolic Labeling and Quantitative Mass Spectrometry
Published on: March 13, 2014
Regulation of electron transport in photosystem-II fragments by magnesium ions
Abstract:
In Photosystem-II reaction-center particles (TSF-IIa) fractionated from spinach chloroplasts by Triton X-100 treatment, divalent cations appear to regulate electron-transport reactions. Oxidation of cytochrome b-559 after illumination of the particles was accelerated by the presence of Mg2+, whereas photoreduction of 2,6-dichlorophenolindophenol (DCIP) by diphenyl carbazide was inhibited, both at a half-effective concentration of Mg2+ of approx. 0.1 mM. The site of regulation was shown to be on the oxidizing side of Photosystem II, near P-680, based on the effects of actinin-light intensity and nature of the electron donors on DCIP photoreduction. Mg2+ was effective in quenching chlorophyll fluorescence in TSF-IIa particles, but the quenching was sensitive to the presence of 3(3,4-dichlorophenyl)-1,1-dimethylurea. In the reaction-center (core) complex of Photosystem II, where the light-harvesting chlorophyll-protein complex is absent, there seems to be no regulation by Mg2+ on excitation-energy distribution.
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