Biophysical Journal 12: 64-79 (1972)
© 1972 the Biophysical Society

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Photochemical Electron Transport in Photosynthetic Reaction Centers from Rhodopseudomonas spheroides

III. Effects of Orthophenanthroline and Other Chemicals

ABSTRACT

Reaction centers from Rhodopseudomonas spheroides mediate the photochemical oxidation of cytochrome c (cyt c), and show a time-varying fluorescence of P870. Analyses of these effects indicate that the reaction centers contain a primary photochemical electron acceptor capable of holding one electron. Native or added ubiquinone (UQ) can act as a secondary electron acceptor. Orthophenanthroline (o-phen) blocks electron transfer from primary to secondary acceptors, and allows the primary acceptor to be exhibited in the foregoing experiments. Other chelators (with the possible exception of 8-hydroxyquinoline) and dichlorophenyldimethylurea (DCMU) are without apparent effect on reaction centers. o-Phen also inhibits the primary photochemical act in reaction centers; this effect is prevented by the presence of UQ. 2-n-Nonyl-4-hydroxyquinoline-N-oxide (NQNO) inhibits the primary photochemistry in reaction centers but does not affect secondary electron transfer.