Spontaneous vesicles of sodium dihexadecylphosphate in HEPES buffer

The formation of spontaneous vesicles of dihexadecylphosphate (DHP) in a HEPES buffered solution at pH 7.4, the size, morphology and melting temperature, obtained by cryogenic transmission electron microscopy (cryo-TEM) and differential scanning calorimetry (DSC), are reported. The vesicles were formed by simply mixing a 5.0 mM lipid-solvent mixture at a temperature (75 degrees C) safely above the higher melting temperature T(m)=70.4 degrees C of DHP. The vesicle diameter ranges from 100 to 332 nm and their geometry is spherical, faceted or oblong. T(m) increases from 66.8 to 70.4 as DHP concentration is raised from 0.6 to 5.0 mM.