Abstract
A method for separating individual monosulfated primary bile acid conjugates by reversed-phase partition thin-layer chromatography on octadecyl-bonded silica gel is described. The solvent system is acetonitrile containing calcium, probably as calcium carbamate. Excellent resolution of the 3- and 7-monosulfated glycine conjugates, as well as 3- and 7-monosulfated taurine conjugates of cholic and chenodeoxycholic acids is reported. A convenient class separation of sulfated from nonsulfated primary bile acid conjugates by adsorption thin-layer chromatography on low-polarity silica gel is also described.
Highlights
The behavior of cholesteryl esters at the airbuffer interface was studied as a function of molecular area and the presence of noncholesterol-containing lipids.The data obtained indicate that cholesterylesters with other than long, saturated acyl groups can be present in surface phases up to packing densities approximately those in natural membranes.Their apparent molecularareas in such phases, which are largely determined by colipid structure, suggest their orientation with the ester function toward the interface
The results obtained help to define the types of interactions necessary for mixed monolayer formation, the structural features governing the degree of miscibility in the surface phase, and the structural requirements for the transport of cholesteryl esters from bulk to surface phases
Our previous study [2] described in detail the application of the two-dimensional phase rule [8, 9] to monolayers comprised of triolein and cholesteryl oleate and is a model for the present study
Summary
The behavior of cholesteryl esters at the airbuffer interface was studied as a function of molecular area and the presence of noncholesterol-containing lipids (colipids).The data obtained indicate that cholesterylesters with other than long, saturated acyl groups can be present in surface phases up to packing densities approximately those in natural membranes.Their apparent molecularareas in such phases, which are largely determined by colipid structure, suggest their orientation with the ester function toward the interface. Reversibility of the monolayer to bulk phase transition is determined exclusively by the acyl structure of the cholesteryl ester. Lipid structures and the behavior of cholesteryl esters in monolayer and bulk phases.J. Lipid Res. 1979. T h e importance of cholesteryl esters in the etiology of atherosclerosis has prompted many studies of their properties in bulk phases. We recently reported the results of studies using cholesteryl oleate and triolein in monolayers at the air- buffer interface which showed these compounds to be miscible up to approximately a 1:1 molar ratio [2]. The cholesteryl oleate was shown to be oriented with its ester function at the air-buffer interface and the cholesterol and fatty acyl moieties occupied approximately the same cross-sectional areas, and presumably orientation, that they do alone and in triglycerides, respectively. The results obtained help to define the types of interactions necessary for mixed monolayer formation, the structural features governing the degree of miscibility in the surface phase, and the structural requirements for the transport of cholesteryl esters from bulk to surface phases
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