Structure of Unilamellar Dimyristoylphosphatidylcholine Vesicle. Small-Angle Neutron Scattering Study

On the basis of the separated form-factor model, a code for fitting the small-angle neutron scattering spectra of the polydispersed vesicle population has been developed. Vesicle and membrane bilayer parameters are analyzed for various hierarchical models of the neutron scattering length density across the membrane. It is shown that hydration of vesicle can be described by a linear distribution function of water molecules. For the first time, the average radius and polydispersity of the vesicle population, thickness of the membrane bilayer, thickness of hydrophobic and hydrophilic parts of bilayer, and water distribution function have been calculated from the SANS experiment, without additional methods such as dynamic light scattering or freeze-fracture electron microscopy. The results, obtained at two different spectrometers, are discussed. The appropriate conditions of the SANS experiment on vesicles are formulated as a necessity to collect the SANS curve in the region of scattering vectors from qmin=0.0033 1/angstrom to qmax=0.56 1/angstrom.