Gel-to-inverted hexagonal (Lβ-HII) phase transitions in phosphatidylethanolamines and fatty acid-phosphatidylcholine mixtures, demonstrated by 31P-NMR spectroscopy and X-ray diffraction

doi:10.1016/0005-2736(82)90245-0

Biochimica et Biophysica Acta (BBA) - Biomembranes

Volume 690, Issue 1, 25 August 1982, Pages 117-123

https://doi.org/10.1016/0005-2736(82)90245-0 Get rights and content

Abstract

The phase behaviour of distearoyl- and dihexadecylphosphatidylethanolamine at high salt concentration and of dipalmitoylphosphatidylcholine +66 mol% palmitic acid at pH 4.0 have been studied by high-field ³¹P-NMR spectroscopy and X-ray diffraction. In saturated NaCl, dihexadecylphosphatidylethanolamine undergoes a reversible transition at 74°C directly from the lamellar gel phase L_β to the inverted hexagonal H_II phase. A similar transition is observed at 78.4°C for distearoylphosphatidylethanolamine in saturated NaCl (cooling scan). The single, sharp calorimetric transition at 61°C observed in dipalmitoylphosphatidylcholine +66 mol% palmitic acid at pH 4.0 also corresponds to a transformation directly from the lamellar gel to the inverted hexagonal phase, without an intervening fluid lamellar phase.

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The rapid insertion of FFA into membranes and their incorporation in more complex molecules enable these acyl chains to induce changes in the structure of lipid bilayers. Since the seventies, the effects of fatty acids on model membrane structure have been studied using a variety of techniques, including differential scanning calorimetry (DSC) (Eliasz et al., 1976; Mabrey and Sturtevant, 1977b; Kantor and Prestegard, 1978b; Schullery et al., 1981), fluorescence spectroscopy (Usher et al., 1978; Klausner et al., 1980; Karnovsky et al., 1982), electron spin resonance (Podo and Blasie, 1976; Marsh and Seddon, 1982), light scattering (Kremer and Wiersema, 1977b), electrophoresis (Hauser et al., 1979), nuclear magnetic resonance (Peter Pauls et al., 1983), scanning densitometry (Fodor and Epand, 1981) and differential thermal analysis (Schullery et al., 1981). Together, these studies have shown that long-chain saturated fatty acids increase the gel-to-fluid phase (Lβ-to-Lα) transition temperature (also known as melting temperature, Tm) of phospholipid bilayers, whereas short chain or cis-unsaturated fatty acids decrease the Tm.
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Gel-to-inverted hexagonal (Lβ-HII) phase transitions in phosphatidylethanolamines and fatty acid-phosphatidylcholine mixtures, demonstrated by 31P-NMR spectroscopy and X-ray diffraction

Abstract

Biochim. Biophys. Acta

Biochim. Biophys. Acta

Biochim. Biophys. Acta

Biophys. J.

Biochim. Biophys. Acta

Gel-to-inverted hexagonal (L_β-H_II) phase transitions in phosphatidylethanolamines and fatty acid-phosphatidylcholine mixtures, demonstrated by ³¹P-NMR spectroscopy and X-ray diffraction