The use of fluorescent probes for studying the interaction of proteins with black lipid membranes.

The number of 1-anilino-8-naphthalene sulphonate (ANS) molecules bound to black phosphatidylcholine (PC) and phosphatidylinositol (PI)-membranes was calculated. The fluorescences change of membrane bound ANS was measured after the additon of positively charged proteins to the same side as ANS. Cytochrome c caused a fluorescence decrease, lysozyme and protamine an increase. These effects were completely reversible in the case of cytochrome c and lysozyme and only partly reversible in the case of protamine by increasing the ionic strength. The fluorescence polarization of membrane bound ANS was not significantly changed by protein addition. The results are discussed with respect to the binding of proteins to black lipid membranes and the use of ANS as a probe compared with other fluorescent probes.