PHOTOBIOELECTRODES ON THE BASIS OF PHOTOSYNTHETIC REACTION CENTERS - STUDY OF EXOGENOUS QUINONES AS POSSIBLE ELECTRON-TRANSFER MEDIATORS

Electrochemical aspects of the functioning of exogenous quinone electron transfer mediators required for developing a photobioelectrode on the basis of photosynthetic reaction centres were studied. Methods for the chemical modification of the Pt and Pt-amalgamated electrodes with a naphthoquinone monolayer were developed and electrochemical reversibility for this immobilized quinone was observed. Moreover, it was found that modification of the Pt surface with cysteamine and especially its amalgamation resulted in an increase in electrochemical reversibility for ubiquinone solubilized in aqueous solution and serving as a diffusionally mobile electron transfer mediator. Adsorption of reaction centres as a monolayer at the electrode surface did not affect the electrochemical properties of the immobilized quinonoid underlayer significantly but limited considerably the electrochemical process for the solubilized electron transfer mediator. The photoelectric activity of bacterial reaction centres adsorbed at various electrode underlayers was studied and was shown to depend significantly on the underlayer type. The results obtained are discussed in connection with the electrochemical properties of quinone electron transfer mediators.