PORE KINETICS REFLECTED IN THE DEQUENCHING OF A LIPID VESICLE ENTRAPPED FLUORESCENT DYE

Pore formation in lipid vesicle membranes can be monitored by the fluo rescence signal F(t) arising from the induced release of a self-quench ing dye in the course of the elapsed efflux time t. We present a basic theoretical analysis of pertinent experimental data allowing the quan titative evaluation of information on the pore kinetics and mechanism. This implies an investigation of the 'dynamic' quenching factor Q(1) exhibited by that fraction of dye which is still being retained inside the liposomes at t. It is shown how Q(1) depends on the mode of relea se which could be 'all-or-none' or more gradual as expressed by a para meter rho less than or equal to 1 (related to the pore lifetime), i.e. , the average dye retention factor in a vesicle after a single pore op ening. A fit to measured values of Q(1) at a sufficient extent of effl ux may be applied in order to determine p. Then the pore formation rat e per liposome, upsilon(a)(t), can be derived from the registered F(t) . We give a practical demonstration of the procedures with carboxyfluo rescein-loaded phosphatidylcholine liposomes of two different sizes to which the wasp venom peptide mastoparan X had been added.