Phase transitions in dipalmitoylphosphatidylcholine-water and dipalmitoylphosphatidylcholine-CaCl2 aqueous solution system by means of a high resolution and high-sensitive differential scanning calorimeter

The phase transitions of dipalmitoylphosphatidylcholine (DPPC)-water and DPPC-CaCl2 aqueous solution system were investigated in the both directions of heating and cooling process by means of a high resolution and high-sensitivity differential scanning calorimeter. The peaks due to the transitions showed different features between heating and cooling runs, especially for the pre-transition and the sample with a high Ca2+ concentration. A sub-main transition in multilamellar bilayers of DPPC was detected in addition to the pre-transition and the main transition. The addition of Ca2+ ion affected the pre-transition and the sub-main transition as well as the main transition.