Study on the Subgel-Phase Formation Using an Asymmetric Phospholipid Bilayer Membrane by High-Pressure Fluorometry

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• 作者：Masaki Goto ; Agnieszka Wilk ; Kosuke Kataoka ; Shirish Chodankar ; Nobutake Tamai ; Makoto Fukui ; Joachim Kohlbrecher ; Hiro-O Ito ; Hitoshi Matsuki
• 刊名：Langmuir
• 出版年：2012
• 出版时间：August 21, 2012
• 年：2012
• 卷：28
• 期：33
• 页码：12191-12198
• 全文大小：443K
• 年卷期：v.28,no.33(August 21, 2012)
• ISSN：1520-5827

文摘

The myristoylpalmitoylphosphatidylcholine (MPPC) bilayer membrane shows a complicated temperature鈥損ressure phase diagram. The large portion of the lamellar gel (L_尾鈥?, ripple gel (P_尾鈥?, and pressure-induced gel (L_尾I) phases exist as metastable phases due to the extremely stable subgel (L_c) phase. The stable L_c phase enables us to examine the properties of the L_c phase. The phases of the MPPC bilayers under atmospheric and high pressures were studied by small-angle neutron scattering (SANS) and fluorescence spectroscopy using a polarity-sensitive fluorescent probe Prodan. The SANS measurements clearly demonstrated the existence of the metastable L_尾I phase with the smallest lamellar repeat distance. From a second-derivative analysis of the fluorescence data, the line shape for the L_c phase under high pressure was characterized by a broad peak with a minimum of ca. 460 nm. The line shapes and the minimum intensity wavelength (位鈥?sub>min) values changed with pressure, indicating that the L_c phase has highly pressure-sensible structure. The 位鈥?sub>min values of the L_c phase spectra were split into ca. 430 and 500 nm in the L_尾I phase region, which corresponds to the formation of a interdigitated subgel L_c (L_cI) phase. Moreover, the phase transitions related to the L_c phase were reversible transitions under high pressure. Taking into account the fluorescence behavior of Prodan for the L_c phase, we concluded that the structure of the L_c phase is highly probably a staggered structure, which can transform into the L_cI phase easily.