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>Investigation of Temperature-Induced Phase Transitions in DOPC and DPPC Phospholipid Bilayers Using Temperature-Controlled Scanning Force Microscopy
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Investigation of Temperature-Induced Phase Transitions in DOPC and DPPC Phospholipid Bilayers Using Temperature-Controlled Scanning Force Microscopy
Under physiological conditions, multicomponent biological membranes undergo structural changes which help define how the membrane functions. An understanding of biomembrane structure-function relations can be based on knowledge of the physical and chemical properties of pure phospholipid bilayers. Here, we have investigated phase transitions in dipalmitoylphosphatidylcholine (DPPC) and dioleoylphosphatidylcholine (DOPC) bilayers. We demonstrated the existence of several phase transitions in DPPC and DOPC mica-supported bilayers by both atomic force microscopy imaging and force measurements. Supported DPPC bilayers show a broad Lβ–Lα transition. In addition to the main transition we observed structural changes both above and below main transition temperature, which include increase in bilayer coverage and changes in bilayer height. Force measurements provide valuable information on bilayer thickness and phase transitions and are in good agreement with atomic force microscopy imaging data. A De Gennes model was used to characterize the repulsive steric forces as the origin of supported bilayer elastic properties. Both electrostatic and steric forces contribute to the repulsive part of the force plot.
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机译:在生理条件下,多组分生物膜会经历结构变化,这有助于确定膜的功能。对生物膜结构-功能关系的理解可以基于对纯磷脂双层的物理和化学性质的了解。在这里,我们研究了二棕榈酰磷脂酰胆碱(DPPC)和二油酰磷脂酰胆碱(DOPC)双层中的相变。通过原子力显微镜成像和力测量,我们证明了DPPC和DOPC云母支撑的双层中存在多个相变。支持的DPPC双层膜表现出宽广的Lβ–Lα过渡。除了主转变以外,我们还观察到了在主转变温度以上和以下的结构变化,包括双层覆盖率的增加和双层高度的变化。力测量提供了有关双层厚度和相变的有价值的信息,并且与原子力显微镜成像数据非常吻合。 De Gennes模型用于表征排斥空间力,将其作为支撑的双层弹性特性的起源。静电力和空间力均会影响力图的排斥部分。
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