Magnetic field-induced fluorescence changes in chlorophyll-proteins enriched with P-700.

Fluorescence yield dependence on external magnetic field (0-600 G) was measured for chlorophyll-protein complexes enriched with Photosystem I. Maximal relative changes of fluorescence yield at room temperature (1.0-2.

Magnetic field affects the fluorescence yield in reaction center preparations from Rhodopseudomonas spaeroides R-26.

Purified photochemical reaction centers from Rhodopseudomonas sphaeroides R-26 were reduced with Na2S2O4 so as to block their photochemical electron-transfer reaction. The magnetic field induced an increase in the emission yield. Our results support the hypothesis that under these conditions, charge recombination in the singlet radical pair composed of the oxidized primary donor and reduced primary acceptor predominantly generates the excited singlet state of the reaction cnter bacteriochlorophyll.