Thermotropic properties of dioleoylphosphatidylethanolamine in aqueous dimethyl sulfoxide solutions.
The effect of dimethyl sulfoxide (DMSO) on the phase behavior and structural parameters of aqueous dispersions of 1,2-dioleoylglycerophosphoethanolamine (DOPE) was characterized using differential scanning calorimetry and time-resolved synchrotron X-ray diffraction. In the range of concentrations of DMSO in water up to 50 wt%, there was a progressive increase in the temperature of the lamellar gel to lamellar liquid-crystal phase transition temperature and a marked decrease in temperature of the transition to the hexagonal II phase. At DMSO concentrations greater than about 25 wt% a direct transition from lamellar gel to hexagonal II structure was observed. A partial phase diagram of the phospholipid in DMSO has been constructed from thermal and X-ray diffraction data. Concentrations of DMSO greater than 50 wt% resulted in the formation of several lamellar crystal phases and interdigitated phases. Phase transition sequences measured on heating included low-temperature exothermic transitions between the interdigitated phase and lamellar crystal phases and an endothermic transition at about 30 degrees C between a lamellar crystal and an interdigitated phase. This latter phase converted directly into an hexagonal II phase at a temperature of about 50 degrees C. On cooling, a second nonbilayer phase (I) first appeared which subsequently reorganized to form a mixture of interdigitated and lamellar crystal phases. The significance of this data in terms of its possible relevance to the biological role of DMSO is discussed.
Yu
Z W
ZW
Division of Life Sciences, King's College London, United Kingdom.
Williams
W P
WP
Quinn
P J
PJ
D055592:Biophysical Phenomena; D001703:Biophysics; D002152:Calorimetry, Differential Scanning; D003451:Cryoprotective Agents / Q000737:chemistry; D004121:Dimethyl Sulfoxide; D005782:Gels; D015394:Molecular Structure; D010714:Phosphatidylethanolamines / Q000737:chemistry*; D012996:Solutions; D013816:Thermodynamics; D014867:Water; D014961:X-Ray Diffraction
D003451:Cryoprotective Agents; D005782:Gels; D010714:Phosphatidylethanolamines; D012996:Solutions; D014867:Water; C020888:1,2-dielaidoylphosphatidylethanolamine; D004121:Dimethyl Sulfoxide