A calorimetric and monolayer investigation of the influence of ions on the thermodynamic properties of phosphatidylcholine

doi:10.1016/0005-2736(75)90350-8

Biochimica et Biophysica Acta (BBA) - Biomembranes

Volume 375, Issue 3, 14 February 1975, Pages 317-326

https://doi.org/10.1016/0005-2736(75)90350-8 Get rights and content

Abstract

The effects of various ions and ²H₂O on the properties of phosphatidylcholine dispersions were studied using differential scanning calorimetry and the change in the surface potential of monolayers with temperature.The phosphatidylcholine in ²H₂O dispersion exhibits a slightly higher transition temperature and lower enthalpy of melting than a phosphatidylcholine in H₂O dispersion. Monovalent (H⁺, Na⁺, and Li⁺) and some divalent cations of chloride salts (Ba²⁺, Mg²⁺, and Sr²⁺) have no effect on the thermal properties of phosphatidylcholine, while halide salts of the di-positive ions Cd²⁺ and Ca²⁺ have no effect on both the enthalpy of melting and transition temperature. No effect attributable to the metal ion was observed in non-halide salts of cadmium. The chloride salt of La³⁺ has no effect on lipid thermal properties whereas that of Fe³⁺ affects the transition temperature. The enthalpy of melting of phosphatidylcholine in one molar solutions of potassium salts increases in the order: $CNS^{−} > acetate > I^{−}$ . Such large, polarizable anions clearly interact with phosphatidylcholine and must therefore also confer a negative charge on the lipid. The potassium salt of SO₄²⁻ has no effect. Possible origins of the observed trends are discussed.

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^∗: Present address: Department of Physiology, Duke University School of Medicine, Durham, N.C. 27710, U.S. A.

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A calorimetric and monolayer investigation of the influence of ions on the thermodynamic properties of phosphatidylcholine

Abstract

Biochim. Biophys. Acta

Electron. Anal. Chem. Interfacial Electro.

J. Biol. Chem.

Chem. Phys. Lipids

Adv. Colloid Interface Sci.

Chem. Phys. Lipids

Biochim. Biophys. Acta

Chem. Phys. Lipids

Biochemistry