Specific heat anomaly in some phospholipids

Abstract The phospholipids exhibit a variety of phase transitions such as gel ⇌ liquid crystalline and pretransition which involves the rotation of the whole hydrocarbon-type chain. These transitions are accompanied by specific heat anomaly. In some situations the order of these transitions is believed to be fractional in nature, and in some other cases the transition has a fine structure which results from the presence of transitions due to the multiple components in the system. In the present communication, Zimm and Bragg theory has been suitably modified to interpret the specific heat measurements in the phosphatidylcholines containing sulfur atoms in thioester and thioether linkages. The thermodynamic parameters associated with the transition are those reported by Hajdu and Sturtevant. The sharpness of transition (△H |MX T c) and the variation of nucleation parameter [sgrave] are consistent with the structural differences in the phospholipids studied. The asymmetry at the tail ends of specific heat is...