Thermotropism and hydration properties of POPE and POPE-cholesterol systems as revealed by solid state2H and31P-NMR |
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Authors: | Radoslav Marinov Erick J Dufourc |
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Institution: | (1) Institute of Solid State Physics, Bulgarian Academy of Sciences, Sofia, Bulgaria;(2) Centre de Recherche Paul Pascal, CNRS, F-33600 Pessac, France |
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Abstract: | The partial phase diagram and the hydration properties of the 1-palmitoyl-2-oleoyl-phosphatidylethanolamine (POPE)-water system, in the absence and presence of 30 mol% cholesterol, have been investigated by solid state phosphorus NMR of the lipid and deuterium NMR of heavy water. The POPE-D2O phase diagram resembles other phosphatidylethanolamine (PE)-water systems: below water-to-lipid molar ratios (Ri) of 3 the lamellar gel (L or Lc)-to-hexagonal type II (HII) phase sequence is observed on increasing the temperature. For Ri 3 the thermotropic sequence (L or Lc)-L -HII is detected. On increasing hydration from Ri=3, the HII phase is detected from 40°C to 85°C whereas the gel phase is observed from 40°C to 30°C. The limiting hydrations of the gel, L and HII phases are Ri 3, 17 and 20, respectively. The number of bound water molecules per lipid is ca. 8 in both the La and HII phases. The presence of cholesterol stabilizes the hexagonal phase 20°C below temperatures at which it is observed in its absence and reduces the limiting hydration of the fluid and hexagonal phases to Ri 9 and 14, respectively. The structure and/or dynamics of the water bound to the interface are markedly modified on going from the L to the HII phase.Abbreviations NMR
Nuclear magnetic resonance
- DDPE
1,2-Didodecyl-rac-glycerol-3-phosphoethanol-amine
- DHPE
1,2-Dihexadecyl-sn-glycerol-3-phosphoethanol-amine
- DOPE
1,2-Dioleoyl-sn-glycerol-3-phosphoethanol-amine
- POPE
1-Palmitoyl-2-oleoyl-sn-glycerol-3-phosphoetha-nolamine
- DAPE
1,2-Diarachinoyl-sn-glycerol-3-phosphoethanol-amine
- DMPC
1,2-Dimyristol-sn-glycerol-3-phosphocholine
- DPPC
1,2-Dipalmitoyl-sn-glycerol-3-phosphocholine
- Tc
lamellar gel-to-lamellar fluid transition temperature
- Th
lamellar fluid-to-hexagonal transition temperature |
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Keywords: | Phosphatidylethanolamine Cholesterol Phase diagram Hydration 2H and 31P NMR |
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