LIGHT-INDUCED ELECTRON TRANSFER IN CHROMATIUM STRAIN D .3. PHOTOPHOSPHORYLATION BY CHROMATIUM CHROMATOPHORES

Photophosphorylation at relatively high rates occurs in light-particle preparations described previously as derived from Chromatium chromatophores. It is shown that the optimal conditions for photophosphyorylation correlate with changes in absorbance established in previous researches as the result of ambient redox potentials between 50 and 100 mV. Effects of various dyes, phenazine methosulfate, oxygen and ascorbate are presented and discussed. Attempts to demonstrate by direct measurement the effective redox potentials for photophosphorylation are described. The evidence accumulated favors occurrence of a cyclic phosphorylation mechanism associated with one of the electron transport pathways (the 'P-890 pathway') postulated in a model presented in a previous paper. © 1968.