[Phases of photoelectrical response of bacteriorhodopsin]

The generation of electrical potential difference by bacteriorhodopsin sheets incorporated into collodium film impregnated with a lecithine solution in decane was studied. The electrical response to a short light flash inducing a single turnover of bacteriorhodopsin consists of four phases. Phase I of photoresponse (tau less than 0.2 mks) has a small amplitude and is directed oppositely to the electrical response to continuous light. The negative phase is followed by positive phases, i.e. microsecond (II) and millisecond (III) ones, either of which can be decomposed at least into two exponents. Phase IV of the electrical response is a passive discharge of capacity of the "bacteriorhodopsin sheets--collodium film" system. Although phases II and III correspond to the generation and disappearance of the photochemical cycle intermediate with an absorption maximum at 412 nm, the parameters and activation energy of these two processes do not show complete coincidence. The effects of gramicidin A and the trifluoromethoxycarbonylcyanidephenylhydrazone uncoupler on the photoelectrical response were analyzed. The data obtained are discussed in terms of an equivalent electrical scheme, according to which the bacteriorhodopsin sheets form closed vesicles upon being incorporated into collodium film.