Unknown

Samples containing 2.6 mmol of phospholipids (DMPCd54 plus either DMPA or DMPG at a 3:1 molar ratio) dissolved in chloroform/methanol (1:1 v/v) were mixed alone or with a-MSH, also in the same solvent, to give a final phospholipid to peptide molar ratio of 10:1. The mixtures were dried under vacuum for 3 h to remove all traces of the organic solvents. Then, multilamellar vesicles (MLV) were formed in 1.4 ml buffer heated at a temperature ;10°C above the temperature of the gel-to-liquid-crystalline phase transition (Tm) of the mixture and frozen at 280°C, this process being repeated five times. Differential scanning calorimetry was performed in a high-resolution Microcal MC-2 calorimeter (Microcal Inc., Northampton, MA). Differences in the heat capacity between the sample and the reference cell were obtained by raising the temperature at a constant rate of 45°C/h over a temperature range of 5–60°C. The excess heat capacity functions were obtained after baseline subtraction and correction for the instrument time response. Unless otherwise stated, the third scan was used for transition temperature and enthalpy calculation