STUDIES ON THE BEHAVIOR OF RHODAMINYL LIP ID PROBES IN MODEL MEMBRANES

The behavior of a series of rhodaminyl lipid probes in model membrane systems is studied. The probes included derivatives of rhodamine 6G (R h6G), rhodamine B (RhB) and rhodamine 101 (Rh101) connected with diole oylglycerol or oleyl hydrophobic residue; unilamellar bilayer vesicles , single-component (from egg yolk phosphatidylcholine) or complex (fro m the mixture phosphatidylcholine - sphingomyelin - cholesterol - dice tyl phosphate, 4:1:2:0.5), were used as model membranes. The kinetic c haracteristics of probe incorporation in the vesicles have been obtain ed. Also, the constants of fluorescence quenching of rhodaminyl probes by iodide have been determined. These data and the values of probe fl uorescence anisotropy in the bilayers allowed to estimate the relative localization of the probes in the membrane. The fluorophore of the pr obe with a dioleoylglycerol hydrophobic moiety is found to be immersed into the bilayer deeper than the same fluorophore bound with the oley l apolar residue. The fluorophore Rh101 is localized deeper in the mem brane than RhB if both of the probes have the same hydrophobic moiety. It is found that in multicomponent vesicles the rhodaminyl probes pro duce clusters at concentrations of 2-3 mol.%. Perylenoyl fluorophore i s found to be an effective donor of excitation energy for rhodaminyls. The Forster radii for all three pairs of perylenoyl - rhodaminyl are determined.