Vesicle Origami and the Influence of Cholesterol on Lipid Packing
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- 作者：Radu Tanasescu ; Martin A. Lanz ; Dennis Mueller ; Stephanie Tassler ; Takashi Ishikawa ; Renate Reiter ; Gerald Brezesinski ; Andreas Zumbuehl
- 刊名：Langmuir
- 出版年：2016
- 出版时间：May 17, 2016
- 年：2016
- 卷：32
- 期：19
- 页码：4896-4903
- 全文大小：427K
- 年卷期：0
- ISSN：1520-5827
文摘
The artificial phospholipid Pad-PC-Pad was analyzed in 2D (monolayers at the air/water interface) and 3D (aqueous lipid dispersions) systems. In the gel phase, the two leaflets of a Pad-PC-Pad bilayer interdigitate completely, and the hydrophobic bilayer region has a thickness comparable to the length of a single phospholipid acyl chain. This leads to a stiff membrane with no spontaneous curvature. Forced into a vesicular structure, Pad-PC-Pad has faceted geometry, and in its extreme form, tetrahedral vesicles were found as predicted a decade ago. Above the main transition temperature, a noninterdigitated Lα phase with fluid chains has been observed. The addition of cholesterol leads to a slight decrease of the main transition temperature and a gradual decrease in the transition enthalpy until the transition vanishes at 40 mol % cholesterol in the mixture. Additionally, cholesterol pulls the chains apart, and a noninterdigitated gel phase is observed. In monolayers, cholesterol has an ordering effect on liquid-expanded phases and disorders condensed phases. The wavenumbers of the methylene stretching vibration indicate the formation of a liquid-ordered phase in mixtures with 40 mol % cholesterol.