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The effect of ice on membrane lipid phase behaviour

1993; Elsevier BV; Volume: 1148; Issue: 2 Linguagem: Inglês

10.1016/0005-2736(93)90140-u

1879-2642

Peter W. Sanderson, W. Patrick Williams, Beth A. Cunningham, D.H Wolfe, L.J. Lis,

Metabolomics and Mass Spectrometry Studies

The effects of ice on the lipid phase behaviour of di-18:1 PE and di-18:2 PE were studied by comparing the behaviour of these lipids in supercooled and frozen dispersions. The presence of ice raised the onset temperature of the Lα → Lβ phase transition of di-18:1 PE from −10°C to −6.5°C and increased its molar enthalpy from 6.1 to 8.5 kcal/mol but had little effect on the co-operativity of the transition. Real-time X-ray diffraction measurements of the HII → Lα phase transition of di-18:2 PE suggested that this transition could take place in the presence of ice but that the corresponding Lα → HII phase transition could not take place until the ice melted. Measurements of the temperature dependence of the d-spacing of di-18:1 PE and di-18:2 PC in frozen dispersions indicated that the amounts of unfrozen water in such dispersions changes significantly with temperature. It was concluded that the increases in onset temperature and molar enthalpy seen for the Lα→Lβ transition of di-18:1 PE probably reflected the effects of osmotic dehydration. The main effect of ice in the case of the HIIåLα phase transition, however, appeared to be to limit the ability of the lipid to undergo structural reorganisation.