Abstract
The phase transitions for dipalmitoylphosphatidylethanolamine (DPPE) dispersed in water and in N-ethylammonium nitrate (EAN) were examined using differential scanning calorimetry and time-resolved x-ray diffraction. Subgel, pre-, and main-phase transitions were observed for DPPE in water, whereas only the pre- and main transitions were observed for DPPE in EAN. Hysteresis was observed for both dispersions upon cooling. In addition, the lamellar (L alpha) to hexagonal (H alpha) phase transition was observed for DPPE dispersed in EAN when using time-resolved x-ray diffraction but not when using calorimetry. This low enthalpy process occurred at 73-77 degrees C, which is significantly lower than that observed for DPPE in water. The presence of EAN stabilizes the existence of the H alpha phase in DPPE by its influence on the bilayer interfacial properties, primarily on the area per lipid head group.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Gruner S. M. Intrinsic curvature hypothesis for biomembrane lipid composition: a role for nonbilayer lipids. Proc Natl Acad Sci U S A. 1985 Jun;82(11):3665–3669. doi: 10.1073/pnas.82.11.3665. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Harlos K. Pretransitions in the hydrocarbon chains of phosphatidylethanolamines. A wide angle X-ray diffraction study. Biochim Biophys Acta. 1978 Aug 17;511(3):348–355. doi: 10.1016/0005-2736(78)90272-9. [DOI] [PubMed] [Google Scholar]
- McDaniel R. V., Simon S. A., McIntosh T. J., Borovyagin V. Interaction of benzene with bilayers. Thermal and structural studies. Biochemistry. 1982 Aug 17;21(17):4116–4126. doi: 10.1021/bi00260a031. [DOI] [PubMed] [Google Scholar]
- McIntosh T. J. Differences in hydrocarbon chain tilt between hydrated phosphatidylethanolamine and phosphatidylcholine bilayers. A molecular packing model. Biophys J. 1980 Feb;29(2):237–245. doi: 10.1016/S0006-3495(80)85128-9. [DOI] [PMC free article] [PubMed] [Google Scholar]
- O'Leary T. J., Levin I. W. Raman spectroscopic study of an interdigitated lipid bilayer. Dipalmitoylphosphatidylcholine dispersed in glycerol. Biochim Biophys Acta. 1984 Oct 3;776(2):185–189. doi: 10.1016/0005-2736(84)90207-4. [DOI] [PubMed] [Google Scholar]
- Seddon J. M., Cevc G., Marsh D. Calorimetric studies of the gel-fluid (L beta-L alpha) and lamellar-inverted hexagonal (L alpha-HII) phase transitions in dialkyl- and diacylphosphatidylethanolamines. Biochemistry. 1983 Mar 1;22(5):1280–1289. doi: 10.1021/bi00274a045. [DOI] [PubMed] [Google Scholar]
- Siegel D. P. Inverted micellar intermediates and the transitions between lamellar, cubic, and inverted hexagonal lipid phases. I. Mechanism of the L alpha----HII phase transitions. Biophys J. 1986 Jun;49(6):1155–1170. doi: 10.1016/S0006-3495(86)83744-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Simon S. A., McIntosh T. J. Interdigitated hydrocarbon chain packing causes the biphasic transition behavior in lipid/alcohol suspensions. Biochim Biophys Acta. 1984 Jun 13;773(1):169–172. doi: 10.1016/0005-2736(84)90562-5. [DOI] [PubMed] [Google Scholar]
- Wilkinson D. A., Nagle J. F. Dilatometry and calorimetry of saturated phosphatidylethanolamine dispersions. Biochemistry. 1981 Jan 6;20(1):187–192. doi: 10.1021/bi00504a031. [DOI] [PubMed] [Google Scholar]
- Wittebort R. J., Blume A., Huang T. H., Das Gupta S. K., Griffin R. G. Carbon-13 nuclear magnetic resonance investigations of phase transitions and phase equilibria in pure and mixed phospholipid bilayers. Biochemistry. 1982 Jul 6;21(14):3487–3502. doi: 10.1021/bi00257a036. [DOI] [PubMed] [Google Scholar]