Phase behavior and glass transition of 1,2-dioleoylphosphatidylethanolamine (DOPE) dehydrated in the presence of sucrose.
The effect of sucrose on the phase behavior of 1,2-dioleoylphosphatidylethanolamine (DOPE) as a function of hydration was studied using differential scanning calorimetry and X-ray diffraction. DOPE/sucrose/water dispersions were dehydrated at osmotic pressures (Pi) ranging from 2 to 300 MPa at 30 degrees C and 0 degrees C. The hexagonal II-to-lamellar gel (H(II)-->L(beta)) thermotropic phase transition was observed during cooling in mixtures dehydrated at Pi<or=35 MPa. After dehydration at Pi>or=57 MPa, the H(II)-->L(beta) thermotropic phase transition was precluded when sucrose entered the rigid glassy state while the lipid was in the H(II) phase. Sucrose also hindered the H(II)-to-lamellar crystalline (L(c)), and H(II)-to-inverted ribbon (P(delta)) lyotropic phase transitions, which occurred in pure DOPE. Although the L(c) phase was observed in dehydrated 2:1 (mole ratio) DOPE/sucrose mixtures, it did not form in mixtures with higher sucrose contents (1:1 and 1:2 mixtures). The impact of sucrose on formation of the ordered phases (i.e., the L(c), L(beta), and P(delta) phases) of DOPE was explained as a trapping of DOPE in a metastable H(II) phase due to increased viscosity of the sucrose matrix. In addition, a glass transition of DOPE in the H(II) phase was observed, which we believe is the first report of a glass transition in phospholipids.
Shalaev
E Y
EY
Department of Crop and Soil Sciences, Cornell University, Ithaca, NY 14853, USA. evgenyi_y_shalaev@groton.pfizer.com
Steponkus
P L
PL
D002152:Calorimetry, Differential Scanning; D008081:Liposomes; D009997:Osmotic Pressure; D010714:Phosphatidylethanolamines / Q000737:chemistry*; D012996:Solutions; D013395:Sucrose / Q000737:chemistry*; D013696:Temperature; D013816:Thermodynamics; D014961:X-Ray Diffraction
D008081:Liposomes; D010714:Phosphatidylethanolamines; D012996:Solutions; D013395:Sucrose; C020888:1,2-dielaidoylphosphatidylethanolamine