[Application of phosphorescent probes in investigations of model and biological membranes]

Possibility of using phosphorescent probes for membrane investigations was analysed on lecithin liposomes and rat liver microsomes taken as an example. It was shown that one quencher molecule on 10(4) lecithin molecules is sufficient for experimental registration of diffusion-controlled quenching of erythrosine phosphorescence by stable nitroxide radicals. It is possible to study the diffusion processes with D = 10(-5) divided by 10(-9) cm2s-1. Application of quenchers of different polarity allows to make a conclusion that the phosphorescent probe erythrosine is localized in liposomes in the region of polar heads of phosphatidyl choline. It was determined from the rate of phosphorescence quenching by radicals that the membrane microviscosity in this region at 20 degrees C equals approximately 1 puas. The coefficient of erythrosine lateral diffusion in liposomes estimated from their self-quenching equals 1,1 x 10(-8) cm2s-1. In the microsome erythrosine is localized in hydrophobic parts of proteins and is not accessible for the quencher molecules.