Incomplete Lipid Chain Freezing of Sonicated Vesicular Dispersions of Double-Tailed Ionic Surfactants

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• 作者：Pieter Saveyn ; Paul Van der Meeren ; Jan Cocquyt ; Torbjö ; rn Drakenberg ; Gerd Olofsson ; Ulf Olsson
• 刊名：Langmuir
• 出版年：2007
• 出版时间：October 9, 2007
• 年：2007
• 卷：23
• 期：21
• 页码：10455 - 10462
• 全文大小：186K
• 年卷期：v.23,no.21(October 9, 2007)
• ISSN：1520-5827

文摘

Lipid freezing in dilute sonicated vesicular dispersions was studied using differential scanning calorimetry (DSC)and ¹H NMR. For charged, anionic, or cationic lipids, approximately half of the lipids remain in a fluid state whencooled 20 C below the main chain melting temperature. With a zwitterionic phospholipid, on the other hand, essentiallyno supercooling of the liquid state was observed. The observations are analyzed in terms of the nucleation and growthof flat solid domains in originally fluid spherical vesicles. As the solid domains grow, the remaining fluid domainis deformed, resulting in a curvature stress. Depending on the vesicle size and the bilayer bending rigidity, the soliddomain growth may terminate as the gain in cohesive free energy is balanced by the curvature stress of the remainingfluid domain. It is argued that high bending rigidities are required for having a significant supercooling, which is whyit is only observed for charged lipids.