Abstract: The photovoltaic response, of the bacteriorhodopsin based sandwich photocell with type of stainless steel/purple membrane film by electrodeposition/Agarose gel/copper, the extraplasmic side faced towards the gel, to continuous light was studied. The polarities of the responses are the same as that of the proton punp under the experimental conditions. The responses were dependence of cationic concentrations in the gel at the extraplasmic side, but the dependence differed from that at the cytoplasmic side. The maximum occured in the plot of the voltage vs the concentration at [K⁺]=75 mmol/L、[Mg²⁺]=1.5 mmol/L, and [La³⁺]=1.5 μmol/L, respectively, in the gel at the extraplasmic side. The shape of the curve of the dependence of voltage on K⁺、 Mg²⁺ or La³⁺ in the gel was similar to that of the quantum efficiency of the proton pump in suspension, respectively. This implication of the relativity was ① the contribution of the photoelectric response of bacteriorhodopsin in the films is due to the proton pump rather than nonproton cations; ② there is a concentration of cation, at which the voltage arrived maxium. The dependence was discussed in the form of the proton domain model and the theory of the diffuse double layer, it may be interpreted by the binding-and screening-effect of metal cations.

Key words: bacteriorhodopsin, photoelectric response dependence of ions proton pump, purple membrane film by electrodeposition