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The effect of ice on membrane lipid phase behaviour
P W Sanderson1, W P Williams, B A Cunningham
1Life Sciences Division, King's College London, Campden Hill, UK.
Biochimica Et Biophysica Acta
|June 5, 1993
Summary
Ice significantly alters lipid phase behavior, increasing transition temperatures and enthalpies for some lipids due to osmotic dehydration. For other lipids, ice restricts structural reorganization, impacting phase transitions.
Area of Science:
- Biophysics
- Materials Science
- Physical Chemistry
Background:
- Lipid phase behavior is critical for biological membranes and drug delivery systems.
- Understanding how environmental factors like ice affect lipid phases is essential for various applications.
Purpose of the Study:
- To investigate the influence of ice on the phase behavior of specific phospholipids: di-18:1 PE and di-18:2 PE.
- To elucidate the mechanisms by which ice affects lipid phase transitions and water structuring.
Main Methods:
- Comparative analysis of lipid dispersions in supercooled and frozen states.
- Real-time X-ray diffraction to monitor phase transitions (Lα↔Lβ and HII↔Lα).
- Temperature-dependent d-spacing measurements to assess unfrozen water content.
Main Results:
- Ice increased the Lα→Lβ transition onset temperature and molar enthalpy for di-18:1 PE, suggesting osmotic dehydration.
- The HII→Lα transition of di-18:2 PE could occur with ice present, but Lα→HII required ice melting.
- Significant changes in unfrozen water content were observed with temperature in frozen lipid dispersions.
Conclusions:
- Osmotic dehydration is a key factor influencing the Lα→Lβ transition of di-18:1 PE in the presence of ice.
- Ice primarily limits the structural reorganization capabilities of lipids during the HII→Lα phase transition.
- The presence and melting of ice play distinct roles in modulating phospholipid phase behavior.