Phase separation of cholesterol from phosphatidylserine-cholesterol mixtures in the presence of the local anesthetic tetracaine

摘要

Addition of the local anesthetic tetracaine (TTC) to multilamellar dispersions of natural phosphatidylserine (PS) causes changes in the thermotropic properties of the membrane, which can be detected by differential scanning calorimetry, and in the structure of the membrane as detected by X-ray diffraction. At molar ratio [PS]/[TTC] similar to 8.5, the melting temperature of the phospholipid shifts downwards by approximately 2.5 degreesC. The melting endotherm is broadened; however, there is little change in the enthalpy of melting. In ternary mixtures (PS-TTC-cholesterol), the thermotropic changes are enhanced. At [PS]/[TTC] similar to 13, the onset of phase separation of cholesterol crystals from PS in the liquid crystalline state occurs at molar fraction cholesterol (X-chol) similar to 0.28, marginally smaller than that found in the absence of the anesthetic. (C) 2004 Elsevier Ireland Ltd. All rights reserved.