title: Gamma-gamma directional correlation study of model membranes.
abstract: Measurements of the perturbed gamma-gamma directional correlation were made for the 173-247 keV cascade in 111Cd at the In ion site in dipalmitoylphosphatidylcholine liposomes. A time-dependent electric quadrupole interaction was observed. Below the order in equilibrium fluid phase transition temperature the exponential damping coefficient was lambda 2 = 0.033 +/- 0.007 ns-1. Above the transition temperature the coefficient was lambda 2 = 0.015 +/- 0.006 ns-1 indicating a twofold increase in molecular mobility in the disordered phase. Absolute values for the motional correlation time, tau c, were estimated to be on the order of a few nanoseconds. The presence of cholesterol was found to cause no significant difference in the molecular mobility of the phosphatidylcholine head groups in the ordered and fluid states.
mesh_terms: D002104:Cadmium; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002784:Cholesterol; D008081:Liposomes; D008433:Mathematics; D008958:Models, Molecular; D008961:Models, Structural; D011663:Pulmonary Surfactants; D013010:Sonication; D013696:Temperature; D013997:Time Factors
chemical_list: D008081:Liposomes; D011663:Pulmonary Surfactants; D002104:Cadmium; D002784:Cholesterol