Effect of dipyridamole on the recombination kinetics of photooxidized bacteriochlorophyll and photoreduced primary quinone in reaction centers of purple bacteria and the decay of bacteriorhodopsin M-412 form

It is shown that the addition of dipyridamole (2,6-bis(diethanolamino)-4,8- dipiperidinopyrimido[5,4d]pyrimidine) (up to 10(-4) M) leads to a drastic a cceleration of the dark recombination reaction between photooxidized bacter iochlorophyll and photoreduced primary quinone in reaction centers of Rhodo bacter sphaeroides. The value of the acceleration is similar to that regist ered under cryogenic temperatures. The extent of the effect of dipyridamole derivatives depended on their structure. In wild-type bacteriorhodopsin an d D96N mutant, dipyridamole slowed down the Schiff base reprotonation (the kinetics of M-412 form decay was registered). It is suggested that dipyrida mole can influence the structural and dynamic state of membrane proteins by affecting the system of their hydrogen-bonds and thus modify electron and proton transport processes.