Phase Changes in Supported Planar Bilayers of 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine

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• 作者：Laura Picas ; M. Teresa Montero ; Antoni Morros ; Gerard Oncins ; Jordi Herná ; ndez-Borrell
• 刊名：Journal of Physical Chemistry B
• 出版年：2008
• 出版时间：August 21, 2008
• 年：2008
• 卷：112
• 期：33
• 页码：10181-10187
• 全文大小：351K
• 年卷期：v.112,no.33(August 21, 2008)
• ISSN：1520-5207

文摘

We studied the thermal response of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) by comparing the differential scanning calorimetry (DSC) data of liposomes with atomic force microscopy (AFM) observations on supported planar bilayers. Planar bilayers were obtained by using the Langmuir−Blodgett (LB) technique: the first leaflet transferred at 30 mN m⁻¹ and the second at 25 mN m⁻¹. The topographic evaluation of supported POPE bilayers above room temperature showed changes between 43.8 and 59.8 °C. These observations are discussed in relation to the main roughness (R_a) variations and are interpreted as the result of the lamellar liquid crystalline (L_α) to inverted hexagonal (H_II) phase transition. High-magnification images obtained at 45 °C revealed intermediate structures in the transformation. Force spectroscopy (FS) was subsequently applied to gain further structural and nanomechanical insight into the POPE planar bilayers as a function of temperature. These measurements show that the threshold force (F_y), which is the maximum force, that the sample can withstand before breaking, increases from 1.91 ± 0.11 nN at 21 °C up to 3.08 ± 0.17 nN at 43.8 °C. This behavior is interpreted as a consequence of the formation of intermediate structures or stalks in the transition from the L_α to H_II phase.