A calorimetric examination of stable and fusing lipid bilayer vesicles

Mixed lipid samples containing dimyristoylglycerophosphocholine and small amounts of myristic acid were examined calorimetrically. Examination of multilamellar and small vesicle samples indicated that upon heating small vesicles combine to form more extended structures. An exothermic peak (at 19 . 5 degrees C) can be associated with the structural transformation. The enthalpy for this process, which may be interpreted as vesicle-vesicle fusion, is found to be approx.--2 kcal/mol.