Dilatometry and calorimetry of saturated phosphatidylethanolamine dispersions

The specific volumes of a series of saturated phosphatidylethanolamine dispersions with 12, 14, and 16 carbon atoms per chain have been measured in the region of the chain melting transition, Tm. The change in specific volume at Tm for the 12 and 14 carbon compounds are 0.0160 and 0.0204 mL/g, respectively. Comparisons are drawn between this class of lipids and phosphatidylcholines. In both cases, Tm extrapolates with increasing chain length to the melting point of polyethylene. Both types of lipids appear to be packed in a similar way below Tm. One major difference is that dilaurylphosphatidylethanolamine undergoes a second transition above Tm.