JULIÁNNA SZAKÁCS*, MELINDA LAKATOS**, CONSTANŢA GANEA***, GY. VÁRÓ**
*Department of Biophysics, University of Medicine and Pharmaceutics, 540139 Tg. Mureş, Romania
**Institute of Biophysics, Biological Research Center of the Hungarian Academy of Sciences, Szeged, H6726, Hungary
***Department of Biophysics, “Carol Davila” University of Medicine and Pharmaceutics, 050474 Bucharest, Romania
Abstract. Kinetic isotope effects in the photochemical reaction cycle of bacteriorhodopsin and pharaonis halorhodopsin were determined in H2O and D2O at normal pH, to get insight in the proton dependent steps of the transport process. All the steps of the bacteriorhodopsin photocycle at normal pH exhibited a strong isotope effect. In the case of halorhodopsin in both the chloride and nitrate transporting conditions the photocycle was not strongly affected by the deuterium exchange. In the case of chloride, a slight slow down of the photocycle could be observed. On the opposite, in the nitrate transport conditions a reverse effect is present.
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