M. DIMA, Z. BÁLINT, CONSTANTA GANEA, G. VÁRÓ

Department of Biophysics, “Carol Davila” University of Medicine and Pharmaceutics, 8, Eroii Sanitari Blvd, 050474 Bucharest, Romania

The electrical signals from Bacteriorhodopsin-containing air dried purple membranes (PM) were recorded at various wavelengths by using a 250 W halogen lamp and narrow band interference filters to excite the probe. The amplitude of the signals was plotted as a function of the wavelength and then compared to the absorption spectrum of dried PMs. The action spectrum thus obtained shows a good correlation with the absorption spectrum in the long wavelengths region but not in the short wavelengths one in contrast to the results obtained in AFM measurements where the correlation was very good at all wavelengths. This puzzling result was tentatively explained taking into account the fact that the samples were excited with continuous light having as a consequence the simultaneous presence of several intermediates of the photocycle, each with a different electrogenicity. Further experiments, employing as exciting laser pulses of various wavelengths, are required in order to elucidate this problem.

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