COORDINATION-COMPOUNDS QUINIC ACID AS DECOUPLERS ON PHOTOSYNTHESIS

We found that quinic acid (1) inhibits ATP-synthesis and the light dependent H+-uptake, it also enhances the basal electron transport rate from water to methylviologen in spinach chloroplasts. These results indicate that it behaves as non-classical decoupler on photophosphorylation. The effect on photosynthetic activities of M(quin)XH2O (M2+ = Co, Ni, X- = Cl; and M(quin)2 (M2+ = Co, Zn, Cd) was studied. The compounds [Co(quin)Cl(H2O)] . H2O (2), Co(quin)2 (3) [Ni(quin)Cl(H2O)] . (H2O)2 (4), [Zn(quin)2] (5) and [Cd(quin)2] (6) inhibit ATP-synthesis, dissipate H+-uptake and accelerate electron transport, behaving as non-classical decouplers. An electronic spectroscopy study of these complexes indicates that they are stable both in water and buffer solutions. The effect of metal salts on photosynthesis was assayed: cobalt chloride has a very mild effect as decoupler, the other metal chlorides (nickel, zinc and cadmium) do not behave as decouplers in freshly lysed chloroplasts.