Differential Scanning Calorimetric Study of the Interaction of Cholesterol with the Major Lipids of the Acholeplasma laidlawii B Membrane

Abstract

It has been proposed that the lower levels of exogenous cholesterol incorporation into the membranes of the sterol-non-requiring as compared to the sterol-requiring mycoplasmas may be due to the much higher glycolipid content of the former and to the reduced ability of glycolipids, as opposed to phospholipids, to incorporate sterols [Efrati et al. (1986) Arch. Biochem. Biophys. 248, 282-288]. In order to test this hypothesis, we have investigated the interaction of cholesterol with the major membrane glyco- and phospholipids of the sterol-non-requiring mycoplasma Acholeplasma laidlawii B, utilizing elaidic acid-homogenous membranes in order to obviate any differences in the nature of cholesterol-lipid interactions due to variations in the fatty acid composition of the different membrane components. Specifically, we have studied the effect of increasing quantities of cholesterol on the thermotropic phase behavior of aqueous dispersions of phosphatidylglycerol, diglucosyl diacylglycerol, and monoglucosyl diacylglycerol, as well as the total membrane polar lipids of this organism, using high-sensitivity differential scanning calorimetry. We find that cholesterol is highly miscible in both the lamellar gel and liquid-crystalline states of phosphatidylglycerol but exhibits limited miscibility in the two neutral glycolipids, particularly in their lamellar gel and crystalline states. We also demonstrate that cholesterol has a limited miscibility in both the lamellar gel and liquid-crystalline states of bilayers composed of the total A. laidlawii B membrane polar lipids. These results demonstrate that the nature of cholesterol-lipid interactions depends markedly on the structure of the glycerolipid polar headgroup and suggests that the incorporation of lower levels of cholesterol into the membranes of the sterol-non-requiring mycoplasmas may indeed be due, at least in part, to their high glycolipid contents. We also show that cholesterol stabilizes the lamellar liquid-crystalline phase of the monoglucosyl diacylglycerol relative to the inverted hexagonal phase at all sterol concentrations, in contrast to the effects of cholesterol on dielaidoylphosphatidylethanolamine, which destabilizes the lamellar liquid-crystalline phase at low concentrations.

Mechanistic investigation of the interaction between bisquaternary antimicrobial agents and phospholipids by liquid secondary ion mass spectrometry and differential scanning calorimetry

“…Doping with aethonium led to both a broadening of the calorimetry peak and to changes in T c and Δ H c (see Table 3). Doping with cholesterol resulted in a considerable broadening of the peak with practically no effect on T c , which has been noted repeatedly in the literature 27,. 36,, 38 Evidently, the substances studied represent examples of quite distinct mechanisms of drug interaction with model membrane structures.…”

“…It is known that the interactions of membranothropic compounds with phospholipid membranes affect some parameters of the gel‐liquid crystal phase transition of membrane phospholipids,36 such as the transition temperature T c , enthalpy of transition Δ H c , and cooperativity of the phase transition which is characterized by the half‐width of the calorimetry peak Δ T c . Furthermore, the nature of variations of these phase transition parameters may give information about the character of the interaction between membranothropic agents and model membranes 27,. 29,, 30,, 36–38…”

“…It is convenient to use model membranes of strictly determined composition that allow us to reveal specific features of the action of the membranothropic agents on the membrane, in particular, the effect of these agents on the phase state of phospholipids in membranes 3,. 27–30 We used the DSC method to obtain insight into the mechanisms of interactions between the antibacterial agents decamethoxinum and aethonium and model phospholipid membranes made from DPPC.…”

Differential Scanning Calorimetric Studies of the Interaction of Cholesterol with Distearoyl and Dielaidoyl Molecular Species of Phosphatidylcholine, Phosphatidylethanolamine, and Phosphatidylserine

“…Phospholipids with strong intermolecular interactions with one another tend to exclude cholesterol from the bilayer above certain critical concentrations. This finding seems also to hold for the MGDG, DGDG, and PG components of the A. laidlawii membrane, where the higher-melting neutral glycolipids exhibit a more limited ability to mix with cholesterol (Monck et al, 1993;McMullen et al, 1996b). The tendency for phospholipid-cholesterol lateral phase separation can be reduced by decreasing the strength of the intermolecular phospholipid-phospholipid interactions.…”

Sistemas miméticos de vesículas da matriz: correlação entre microambiente lipídico e a atividade da fosfatase alcalina no processo de biomineralização

“…Assim, muitos estudos sobre a interação do Chol com monocamada de fosfolipídios e modelos de membranas de bicamada foram realizados, utilizando uma grande variedade de técnicas (Demel e De Kruyff, 1976; Vist e Davis, 1990;Mcmullen e Mcelhaney, 1996;, na sequência dos estudos de DSC pioneiros de Chapman (Ladbrooke et al, 1968) e de Sturtevant (Hinz e Sturtevant, 1972). A SM apresenta-se como um componente estrutural nas biomembranas juntamente com outros fosfolipídios, glicolipídios, Chol e algumas proteínas integrais de membrana.…”