Dansyl lysine: a structure-selective fluorescent membrane stain?
Dansyl lysine (DL) is a fluorescent compound that has significantly higher solubility in synthetic phosphatidylcholine (PC) membranes with a low cholesterol content than it does in water or in membranes having a high cholesterol content. Its fluorescence intensity is enhanced at least 50-fold when dissolved in PC membranes. Therefore, membranes with mole fractions of cholesterol (Xch) less than or equal to 0.5-0.3 are stained by aqueous solutions of DL: those with a higher cholesterol content, 0.3-0.4 less than or equal to Xch less than or equal to 0.5, are not. It is proposed that DL selects for a structural feature of membranes: cholesterol-free domains. The phenomenon has provided evidence for long-lived compositional heterogeneity in large multilamellar PC-cholesterol liposomes having Xch less than or equal to 0.2. This is not consistent with a model in which the homogeneous state is thermodynamically favored and both intermembrane transfer and transmembrane transfer (flip-flop) of cholesterol are fast. These studies are of potential importance for understanding cell membrane structure, in particular lipid-phase equilibria and the maintenance of compositional heterogeneity between the different membranes of cells.
D002784:Cholesterol; D004134:Dimyristoylphosphatidylcholine; D005456:Fluorescent Dyes; D008051:Lipid Bilayers; D008081:Liposomes; D008239:Lysine / Q000031:analogs & derivatives*; D008566:Membranes / Q000648:ultrastructure; D008954:Models, Biological; D010713:Phosphatidylcholines
D005456:Fluorescent Dyes; D008051:Lipid Bilayers; D008081:Liposomes; D010713:Phosphatidylcholines; C036851:dansyllysine; D002784:Cholesterol; D008239:Lysine; D004134:Dimyristoylphosphatidylcholine