Abstract
We used x-ray and neutron diffraction to study the temperature- and pressure-dependent structure and phase behavior of the monoacylglycerides 1-monoelaidin (ME) and 1-monoolein (MO) in excess water. The monoacylglycerides were chosen for investigation of their phase behavior because they exhibit mesomorphic phases with one-, two-, and three-dimensional periodicity, such as lamellar, an inverted hexagonal and bicontinuous cubic phases, in a rather easily accessible temperature and pressure range. We studied the structure, stability, and transformations of the different phases over a wide temperature and pressure range, explored the epitaxial relations that exist between different phases, and established a relationship between the chemical structure of the lipid molecules and their phase behavior. For both systems, a temperature-pressure phase diagram has been determined in the temperature range from 0 to 100 degrees C at pressures from ambient up to 1400 bar, and drastic differences in phase behavior are found for the two systems. In MO-water dispersions, the cubic phase Pn3m extends over a large phase field in the T,p-plane. At temperatures above 95 degrees C, the inverted hexagonal phase is found. In the lower temperature region, a crystalline lamellar phase is induced at higher pressures. The phases found in ME-water include the lamellar crystalline Lc phase, the L beta gel phase, the L alpha liquid-crystalline phase, and two cubic phases belonging to the crystallographic space groups Im3m and Pn3m. In addition, the existence of metastable phases has been exploited. Between coexisting metastable cubic structures, a metric relationship has been found that is predicted theoretically on the basis of the curvature elastic energy approximation only.
Full text
PDF
Images in this article
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Briggs J., Caffrey M. The temperature-composition phase diagram of monomyristolein in water: equilibrium and metastability aspects. Biophys J. 1994 Mar;66(3 Pt 1):573–587. doi: 10.1016/s0006-3495(94)80847-1. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Caffrey M. Kinetics and mechanism of transitions involving the lamellar, cubic, inverted hexagonal, and fluid isotropic phases of hydrated monoacylglycerides monitored by time-resolved X-ray diffraction. Biochemistry. 1987 Oct 6;26(20):6349–6363. doi: 10.1021/bi00394a008. [DOI] [PubMed] [Google Scholar]
- Chung H., Caffrey M. The curvature elastic-energy function of the lipid-water cubic mesophase. Nature. 1994 Mar 17;368(6468):224–226. doi: 10.1038/368224a0. [DOI] [PubMed] [Google Scholar]
- Lindblom G., Brentel I., Sjölund M., Wikander G., Wieslander A. Phase equilibria of membrane lipids from Acholeplasma laidlawii: importance of a single lipid forming nonlamellar phases. Biochemistry. 1986 Nov 18;25(23):7502–7510. doi: 10.1021/bi00371a037. [DOI] [PubMed] [Google Scholar]
- Lutton E. S. Phase behavior of aqueous systems of monoglycerides. J Am Oil Chem Soc. 1965 Dec;42(12):1068–1070. doi: 10.1007/BF02636909. [DOI] [PubMed] [Google Scholar]
- Mariani P., Luzzati V., Delacroix H. Cubic phases of lipid-containing systems. Structure analysis and biological implications. J Mol Biol. 1988 Nov 5;204(1):165–189. doi: 10.1016/0022-2836(88)90607-9. [DOI] [PubMed] [Google Scholar]
- McIntosh T. J., Magid A. D., Simon S. A. Repulsive interactions between uncharged bilayers. Hydration and fluctuation pressures for monoglycerides. Biophys J. 1989 May;55(5):897–904. doi: 10.1016/S0006-3495(89)82888-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Seddon J. M. Structure of the inverted hexagonal (HII) phase, and non-lamellar phase transitions of lipids. Biochim Biophys Acta. 1990 Feb 28;1031(1):1–69. doi: 10.1016/0304-4157(90)90002-t. [DOI] [PubMed] [Google Scholar]
- So PT, Gruner SM, Erramilli S. Pressure-induced topological phase transitions in membranes. Phys Rev Lett. 1993 May 31;70(22):3455–3458. doi: 10.1103/PhysRevLett.70.3455. [DOI] [PubMed] [Google Scholar]
- Tate M. W., Eikenberry E. F., Turner D. C., Shyamsunder E., Gruner S. M. Nonbilayer phases of membrane lipids. Chem Phys Lipids. 1991 Mar;57(2-3):147–164. doi: 10.1016/0009-3084(91)90073-k. [DOI] [PubMed] [Google Scholar]
- Wiener M. C., Tristram-Nagle S., Wilkinson D. A., Campbell L. E., Nagle J. F. Specific volumes of lipids in fully hydrated bilayer dispersions. Biochim Biophys Acta. 1988 Feb 18;938(2):135–142. doi: 10.1016/0005-2736(88)90153-8. [DOI] [PubMed] [Google Scholar]