The effect of head group structure on phase transition of phospholipid membranes as determined by differential...

The phase transition characteristics of cardiolipin and phosphatidylglycerol suspensions were investigated by differential scanning calorimetry. The phase transition temperatures for dimyristoylphosphatidylglycerol, tetramyristoylcardiolipin, dipalmitoylphosphatidylglycerol and tetrapalmitoylcardiolipin were 25.0, 47.0, 40.5 and 62.2 degrees C, respectively. The phase transition temperature for a mixture of two analogous phospholipids was higher than that for phosphatidylglycerol alone, but lower than that for cardiolipin alone. It increased along with cardiolipin content. The phase transition temperature for cardiolipin was increased in the presence of divalent cations, particularly Ca2+. The results indicate that the head group of cardiolipin by itself can increase the phase transition temperature.