Effect of stereoconfiguration on ripple phases (P beta') of dipalmitoylphosphatidylcholine. 
Mixtures of sn-1 (D) and sn-3 (L) enantiomers of fully hydrated dipalmitoylphosphatidylcholine (DPPC) were studied with differential scanning calorimetry and freeze-fracture microscopy.  The pretransition temperature of racemic mixtures of DPPC was 1.8 C degrees below that of either pure sn-1 or sn-3 enantiomers, which had similar pretransition temperatures.  The main transition temperature of racemic mixtures was also depressed, but to a lesser extent, 0.8 C degrees.  Freeze-fracture images of liposomes of sn-1, sn-3, and racemic mixtures of DPPC frozen from the P beta' phase showed well-defined ripples of wavelength 13 nm.  Lipid stereoconfiguration had no effect on ripple wavelength, configuration or amplitude, or on the number and nature of surface defects.