Phase Transitions in Dipalmitoylphosphatidylcholine Monolayers

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• 作者：Yi Y. Zuo ; Rimei Chen ; Xianju Wang ; Jinlong Yang ; Zdenka Policova ; A. Wilhelm Neumann
• 刊名：Langmuir
• 出版年：2016
• 出版时间：August 23, 2016
• 年：2016
• 卷：32
• 期：33
• 页码：8501-8506
• 全文大小：464K
• 年卷期：0
• ISSN：1520-5827

文摘

A self-assembled phospholipid monolayer at an air–water interface is a well-defined model system for studying surface thermodynamics, membrane biophysics, thin-film materials, and colloidal soft matter. Here we report a study of two-dimensional phase transitions in the dipalmitoylphosphatidylcholine (DPPC) monolayer at the air–water interface using a newly developed methodology called constrained drop surfactometry (CDS). CDS is superior to the classical Langmuir balance in its capacity for rigorous temperature control and leak-proof environments, thus making it an ideal alternative to the Langmuir balance for studying lipid polymorphism. In addition, we have developed a novel Langmuir–Blodgett (LB) transfer technique that allows the direct transfer of lipid monolayers from the droplet surface under well-controlled conditions. This LB transfer technique permits the direct visualization of phase coexistence in the DPPC monolayer. With these technological advances, we found that the two-dimensional phase behavior of the DPPC monolayer is analogous to the three-dimensional phase transition of a pure substance. This study has implications in the fundamental understanding of surface thermodynamics as well as applications such as self-assembled monolayers and pulmonary surfactant biophysics.