Interaction between Ca2+ and dipalmitoylphosphatidylcholine membranes. II. Fluorescence anisotropy study.
The effect of Ca2+ on the molecular mobility in dipalmitoylphosphatidylcholine membranes was studied by steady-state and time-resolved measurements of fluorescence anisotropy. The fluorescence anisotropy decay of 1,6-diphenyl-1,3,5-hexatriene in the hydrocarbon region indicated that the free volume of molecular rotation became more restricted when the Ca2+ concentration was increased. The decrease of the molecular mobility was observed from 1 mM Ca2+, at which the number of bound Ca2+ is much less than that of the total lipid molecules. A distinct difference between Ca2+ and Mg2+ effects suggested that the change in various membrane properties was induced by the binding of these ions. From these results we propose a long-range attractive interaction between bound Ca2+ and the polar head groups of distant phosphatidylcholine molecules.
D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002413:Cations, Divalent; D003619:Dansyl Compounds; D004161:Diphenylhexatriene; D005454:Fluorescence Polarization; D005456:Fluorescent Dyes; D008051:Lipid Bilayers / Q000378:metabolism; D008081:Liposomes / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology; D008560:Membrane Fluidity / Q000187:drug effects; D010714:Phosphatidylethanolamines; D011663:Pulmonary Surfactants / Q000378:metabolism*; D013696:Temperature
D002413:Cations, Divalent; D003619:Dansyl Compounds; D005456:Fluorescent Dyes; D008051:Lipid Bilayers; D008081:Liposomes; D010714:Phosphatidylethanolamines; D011663:Pulmonary Surfactants; D004161:Diphenylhexatriene; C024284:dansyl phosphatidylethanolamine; D008274:Magnesium; D002118:Calcium