[The effect of surface and membrane potential on 1-anilino-8-naphthalenesulfonate binding with E. coli membrane]

Dependence of ANS fluorescence on the surface potential of E. coli under lowered resistance of the bacterial membrane and after application of the positive diffusion potential inside the cell was investigated. It was shown that in the absence of the latter ANS binding in de-energised bacteria occurs mainly at the outside surface. It may be due to the high negative charge of the inner side of the cytoplasmic membrane. According to produced evaluation the potential of this surface is 120 +/- 25 mV. The data obtained suggest that low ANS fluorescence in intact cells is due to the membrane modification on energisation.