Differential scanning calorimetry and 1H-NMR study of aqueous dispersions of the mixtures of dipalmitoylphosphatidilcholine and phosphatidylinositol-4,5-bis(phosphate)

Thermal phase transitions of aqueous dispersions of phospholipid mixtures of phosphatidylinositol-4,5-bis(phosphate) (PIP2) and dipalmitoyl-phosphatidylcholine (DPPC) were studied by using differential scanning calorimetry (DSC) and proton nuclear magnetic resonance spectroscopy (H-1-NMR). The DSC curves are classified into three different types in their endothermic profiles according to the molar ratio of PIP2/DPPC. From the results of DSC and H-1-NMR, three different types of structural regions are distinguished in the aqueous dispersions of mixtures of DPPC and PIP2; (I) Region of DPPC with some defects produced by insertion of a small amount of PIP2, (II) region of DPPC-PIP2 complexes and (III) pure domain of PIP2. (C) 1998 Elsevier Science B.V.