RIPPLE WAVELENGTH, AMPLITUDE, AND CONFIGURATION IN LYOTROPIC LIQUID CRYSTALS AS A FUNCTION OF EFFECTIVE HEADGROUP SIZE.

We present differential scanning calorimetry (DSC) and freeze-fracture electron micrographs of the P// beta // prime phase of dimyristoylphosphatidylcholine (DMPC) multilamellar liposomes in excess water with varying fractions of N-methyl substituted dimyristoylphosphatidylethanolamine (DMPE). Two distinct ripple configurations are observed at all DMPE fractions that exhibited a P//63 // prime phase; an asymmetric ripple of wavelength 12. 0 nm and amplitude less than 6 nm and a symmetric ripple of incommensurate wavelength 22. 0 nm and an amplitude of at least 9 nm. Defects, such as disclinations and grain boundaries are stabilized by DMPE, but the ripple shapes, wavelength and amplitudes are unaffected. DMPE also seems to prevent the annihilation of the ripples below the pretransition. The results are discussed in relation to continuum description of the P//63 // prime phase.