Phase diagram of 1,2-dioleoylphosphatidylethanolamine (DOPE):water system at subzero temperatures and at low water contents

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• 作者：Shalaev ; Evgenyi Y. ; Steponkus ; Peter L.
• 关键词：Phosphatidylethanolamine ; Differential scanning calorimetry ; X-ray diffraction ; Phase diagram ; Water sorption ; Ice melting ; PC ; phosphatidylcholine ; PE ; phosphatidylethanolamine ; DOPE ; 1 ; 2-dioleoyl-sn-glycero-3-phosphatidylethanolamine ; DDPE ; 1 ; 2-didodecy
• 刊名：Biochimica et Biophysica Acta (BBA)/Biomembranes
• 出版年：1999
• 出版时间：July 15, 1999
• 年：1999
• 卷：1419
• 期：2
• 页码：229-247
• 全文大小：557 K

文摘

The phase behavior of partially hydrated 1,2-dioleoylphosphatidylethanolamine (DOPE) has been studied using differential scanning calorimetry and X-ray diffraction methods together with water sorption isotherms. DOPE liposomes were dehydrated in the H_II phase at 29°C and in the L_α phase at 0°C by vapor phase equilibration over saturated salt solutions. Other samples were prepared by hydration of dried DOPE by vapor phase equilibration at 29°C and 0°C. Five lipid phases (lamellar liquid crystalline, L_α; lamellar gel, L_β; inverted hexagonal, H_II; inverted ribbon, P_δ; and lamellar crystalline, L_c) and the ice phase were observed depending on the water content and temperature. The ice phase did not form in DOPE suspensions containing <9 wt % water. The L_c phase was observed in samples with a water content of 2–6 wt % that were annealed at 0°C for 2 or more days. The L_c phase melted at 5–20°C producing the H_II phase. The P_δ phase was observed at water contents of <0.5 wt % . The phase diagram, which includes five lipid phases and two water phases (ice and liquid water), has been constructed. The freeze-induced dehydration of DOPE has been described with the aid of the phase diagram.