Growth of Molecular Superlattice in Fully Hydrated Dipalmitoylphosphatidylcholine during Subgel Phase Formation Process

Recently, it has been reported that the structure of the subgel phase of dipalmitoylphosphatidylcholine (DPPC) is characterized by two lattices, i.e., a hydrocarbon lattice and a molecular superlattice [1]. On the basis of the results, the domain growth of the molecular superlattice in fully hydrated DPPC multilamellar vesicles at 2.5 degrees C was studied by means of X-ray diffraction. The change of the intensities of the (11) diffraction peak originated from the molecular superlattice was analyzed by the Kolmogorov-Avrami theory. We found that the effective dimensionality of the growing domains is 2.3 +/- 0.4. This result indicates that the domains of the molecular superlattice grow two-dimensionally during the subgel phase formation process, i.e., the domain grows in a single bilayer and is independent between the domains in adjacent bilayers.