KINETIC-ANALYSIS OF LIGHT-INDUCED PROTON DISSOCIATION AND ASSOCIATIONOF BACTERIORHODOPSIN IN PURPLE MEMBRANE-FRAGMENTS UNDER CONTINUOUS ILLUMINATION

In the present work the photo responses of bacteriorhodopsin in purple membrane fragments were studied under continuous high intensity light illumination in different ranges of pH, temperature and ionic strengt h. The activity of bacteriorhodopsin was measured as pH vs. time by us ing a combined pH electrode, The activity of the bacteriorhodopsin in purple membrane fragments at acidic pH was found to be more sensitive to temperature changes than it was at physiological or higher pH value s. The activity of bacteriorhodopsin was also found to be the function of varing concentrations of different salts. The kinetic analyses of light reactions (proton dissociation) and dark reactions (proton assoc iation) were carried out at different pH, temperature and ionic streng ths, The kinetic data revealed that the proton dissociation in the lig ht and proton association in the dark followed the first order kinetic s in the pH range of 6.7-7.2 at room temperature, Beyond these limits the kinetic behavior of bacteriorhodopsin was found to be much more co mplex.