Photon correlation spectroscopy study on the stability of small unilamellar DPPC vesicles

The growth in size of dipalmitoylphosphatidylcholine small unilamellar vesicles (SUV) below Tm has been studied by photon correlation spectroscopy and differential scanning calorimetry. We see an initial fast rise of the hydrodynamic diameter of the vesicles followed by a slower increase. We assign the slow component of the size change to fusion of SUV. The order of the kinetics appears to be higher than first order. The estimated half lifetime of the fusion is approximately 67 h. The diameters for the fast and slow processes at t = O are 756 and 256 A, respectively, while as t leads to infinity the diameters increase to 1,570 and 733 A, respectively.