Ca2+ induced phase separations in phospholipid mixtures.
We have probed the character of the observed phase separation in mixtures of phosphatidylcholines (PC) and/or phosphatidylethanolamines (PE) in the presence of CaCl2 solutions. Egg yolk phosphatidylethanolamine (EYPE) and a 1:1 molar ratio of dioleoylphosphatidylcholine/dioleoylphosphatidylethanolamine (DOPC/DOPE) were observed to undergo phase separation in CaCl2 solutions, as was previously observed for egg yolk phosphatidylcholine (EYPC) (L.J. Lis et al. Biochemistry, 20 (1981) 1771-1777). However, the mixed chain lipid, palmitoyloleoyl-PC, yielded only a single phase in water or CaCl2 solution. We hypothesize that two lipid species are necessary for the observed phase separation to occur, but that the separation itself is not a function of the individual lipid species, but of the mixture.
D002118:Calcium; D002784:Cholesterol; D007700:Kinetics; D008051:Lipid Bilayers; D008954:Models, Biological; D010713:Phosphatidylcholines; D013329:Structure-Activity Relationship; D014961:X-Ray Diffraction
D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D002784:Cholesterol; D002118:Calcium