[Kinetics of primary photocycle stages of bacteriorhodopsin at low temperatures]

According to the changes of absorption spectra kinetics of two primary stages of bacteriorhodopsin photochemical cycle was studied in the temperature range 160 +/- 300 degrees K. It has been found that for K610-L550 transition in the range under study the rate-temperature relationship is described by Arrhenius law with the activation energy Ea = 0.68 eV. For L550-M412 transition Ea = 0.69 eV. The character of temperature relationship, of the rate and amplitude for this transition indicates that at T less than or equal to 270 degrees K a phase transition is possible.