[Photophosphorylation involving chlorophyll adsorbate, separation of light and dark stages]

Upon illumination of the system containing chlorophyll a+b adsorbed on a SiO2 sorbent, ADP and Pi in an aqueous solution, pH 7.6, the formation of ATP has been demonstrated, using 32P-phosphate. This process is inhibited in the absence of oxygen or in the presence of ascorbate. Under similar conditions without ADP pyrophosphate is formed; substitution of ADP for arginine results in a formation of arginine phosphate. Phosphorylation with a reduced yield has also been found upon illumination of chlorophyll adsorbate without other additives and an addition of ADP+Pi solution in the dark to the preilluminated adsorbate fast enough to prevent the decay of the light-induced product. A model according to which the chlorophyll-sensitized oxidation of orthophosphate ion the primary event in the reaction sequence, and the decomposition of orthophosphate radical anion into methaphosphate and hydroxyl species is the secondary step, has been proposed. A possible significance of the results obtained is discussed in terms of the concepts on the prebiotic evolution of energy metabolism.