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.
Zasadzinski
J A
JA
Department of Chemical and Nuclear Engineering, University of California, Santa Barbara 93106.
D015060:1,2-Dipalmitoylphosphatidylcholine; D002152:Calorimetry, Differential Scanning; D005614:Freeze Fracturing; D008051:Lipid Bilayers; D008081:Liposomes; D008854:Microscopy, Electron; D013237:Stereoisomerism; D013696:Temperature; D013816:Thermodynamics
D008051:Lipid Bilayers; D008081:Liposomes; D015060:1,2-Dipalmitoylphosphatidylcholine