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J M Smaby

Publications and source records attributed to J M Smaby.

24 records · Page 2Linked to original sources
PubMed1981

Novel surface phase containing cholesteryl esters. 1. Structural characteristics determined from surface pressure--area measurements.

The behavior of cholesteryl myristoleate in mixtures with dioleoylphosphatidylcholine was investigated at the air--water interface. In addition to the previously described monolayer phase [Smaby, J. M., Baumann, W. J., & Brockman, H. L. (1979) J. Lipid Res. 20, 789--795], a second surface phase has been identified. Analysis of surface pressure and molecular area data as a function of composition shows that the molecules in the second phase can exist in two miscible, double-layer states or packing arrangements, only one of which contains lecithin. The mixed double-layer state is preferentially formed and has stoichiometry ranging between 2.0 and 9.5 molecules of cholesteryl ester for each lecithin molecule. The structure of this state resembles a mixed monolayer of pressure-dependent composition and area which is covered by a second layer of cholesteryl ester at 38.2 A2/molecule. The cholesteryl myristoleate/lecithin ratio of the layer in contact with the aqueous phase ranges from 0 to 2.8 between 39 and 0 mN/m. The second double-layer state is equivalent to a monolayer of cholesteryl ester at the lipid--water interface, covered by a layer of cholesteryl ester molecules at 38.2 A2. Overall, our data show that the presence of lecithin at a lipid--water inferface has a definite ordering effect on cholesteryl ester molecules at least 30--50 A from the interface.

Chemical Phenomena↗
PubMed1981

Novel surface phase containing cholesteryl esters. 2. Nonequivalence of cholesteryl arachidonate and those with 18-carbon, cis-unsaturated acyl groups.

Surface pressure--area isotherms for binary mixtures of cholesteryl octanoate, elaidate, stearate, oleate, linoleate, linolenate, and arachiodonate in mixtures with dioleoyllecithin, triolein, oleic acid, and oleoyl alcohol were measured at 24 degrees C. Analysis of the pressure and area characteristics as a function of composition showed that double-layer surface phase formation is primarily dependent on the structure of the acyl moiety of the cholesteryl ester. Cholesteryl esters with saturated or trans-unsaturated acyl chains apparently do not form double-layer surface phases. The esters of oleate, linoleate, and linolenate formed double-layer as well as monolayer phases and their properties in these phases were similar. In contrast to other cis-unsaturated esters, cholesteryl arachidonate formed a mixed monolayer phase with miscibility in all proportions and did not form a double-layer phase. Our results show that the polar lipid monolayer separating bulk cholesteryl ester from the aqueous milieu not only solubilizes finite amounts of cholesteryl esters but also can contribute to the organization of lipid adjacent to the monolayer. That such organization is observed with the predominant cholesteryl ester species of blood and aorta suggests a role for double-layer structure in regulating the transport and metabolism of cholesteryl esters in lipoproteins, arterial lipid deposits, and adrenal cortex. The absence of double-layer formation and high monolayer solubility of cholesteryl arachidonate suggest that it should be more abundant than other cholesteryl esters in bilayers and in monolayers surrounding bulk lipid phases.

Arachidonic Acids↗
PubMed1979

Interfacial structure and lipase action. Characterization of taurodeoxycholate-didecanoylglycerol monolayers by physical and kinetic methods.

Surface pressure-area isotherms for 1,3-didecanoyl-glycerol (dicaprin) were determined as a function of the concentration of taurodeoxycholate in the subphase. Analysis of these curves indicates that, from 0.05 to 0.80 mM bile salt, surface structure is dependent only on the surface concentration of the diglyceride. The limiting areas for dicaprin in the presence and absence of bile salt were about 38 A2/molecule. Subjecting the monolayers to hydrolysis by pancreatic lipase yielded kinetic data which, together with the physical studies, support a model for monolayer glyceride molecules undergoing discrete changes of state. In the absence of bile salt, the relatively expanded state exhibits an area of 75 A2/diglyceride molecule and is not a substrate for pancreatic lipase B. The more condensed state exhibits an area of 38 A2/diglyceride molecule and is hydrolyzed at a rate proportional to its concentration in the monolayer. Taurodeoxybholate at 0.05 to 0.60 mM shifts the apparent area of the expanded state to 360 A2/diglyceride molecule.

Animals↗
PubMed1979

Lipid structure and the behavior of cholesteryl esters in monolayer and bulk phases.

The behavior of cholesteryl esters at the air-buffer interface was studied as a function of molecular area and the presence of noncholesterol-containing lipids (colipids). The data obtained indicate that cholesteryl esters with other than long, saturated acyl groups can be present in surface phases up to packing densities approximately those in natural membranes. Their apparent molecular areas in such phases, which are largely determined by colipid structure, suggest their orientation with the ester function toward the interface. The extent of miscibility in the surface phase is also a strong function of colipid structure. Reversibility of the monolayer to bulk phase transition is determined exclusively by the acyl structure of the cholesteryl ester. Of the esters examined, only those with cis unsaturation collapsed reversibly. Our data predict that cholesteryl esters should be present in small, but finite amounts on the surface of arterial lipid deposits and that a prerequisite for the removal of such deposits is that the bulk lipid phase be in a liquid or liquid crystalline state.

Chemical Phenomena↗
PubMed1978

Properties of cholesteryl oleate and triolein in mixed monolayers at the air-water interface.

The properties of cholesteryl oleate and triolein in mixed monolayers at the air-water interface have been measured between 24 and 37 degrees C. Analysis of force-area curves obtained as a function of the mol fraction of cholesteryl oleate indicates that at relatively low surface pressures these compounds are miscible in two dimensions up to a limit of about 0.5 mol fraction. At higher pressures either cholesteryl oleate or both lipids are expelled from the monolayer to form a bulk phase which is in rapid equilibrium with the surface phase. In the monolayer phase, orientation of the ester function of cholesteryl oleate is toward the aqueous phase, interaction with triolein is minimal, and packing is uniform over the solubility range. This together with the susceptibility of the cholesteryl oleate to enzymatic hydrolysis, suggests the applicability of monolayer systems to the study of cholesterol esterase activity. Comparison of our results with the bulk properties of these lipids suggests that the expelled cholesteryl oleate exists as a smectic mesophase and thus the system may provide a model for studying the transfer of molecules between the interior and surface of lipid deposits of the type found in atherosclerotic lesions.

Cholesterol Esters↗