摘要 在由膽固醇與高、低熔點脂質組成的三元混合物中，脂質膜於接近組成臨界點時會產生臨界波動，進而影響其物理性質。先前研究已指出臨界波動與膜融合之間存在高度關聯，但其機制尚未明確。本研究藉由調整組成、溫度與滲透壓，並利用小角度X光散射 (SAXS) 測量各類結構參數，以探討臨界波動對脂雙層間交互作用力的影響。結果顯示，從液態有序相通過臨界點往液態無序相接近時，水合斥力會逐漸減小。水層厚度隨升溫的變化在臨界點前後有顯著的差異，我們認為與臨界波動的影響有關，並進一步推論液態有序相相較液態無序相更受波動斥力影響，而在液態無序相中則可能有一未知的排斥力存在影響膜與膜之間的交互作用。這些發現有助於了解臨界波動在膜融合過程中的影響，並建立脂質膜臨界行為與膜間交互作用之間的關聯。 ;Abstract In ternary mixtures composed of cholesterol with high- and low-melting-temperature lipids, lipid membranes exhibit critical fluctuations when approaching the compositional critical point, thereby influencing their physical properties. Previous studies have indicated a strong correlation between critical fluctuations and membrane fusion, yet the underlying mechanism remains unclear. In this study, we modulated composition, temperature, and osmotic pressure and employed small-angle X-ray scattering (SAXS) to measure structural parameters in order to investigate the effect of critical fluctuations on interbilayer interactions. The results show that as the system approaches the liquid-disorder phase through the critical point from the liquid-order phase, the hydration repulsion gradually decreases. The changes in water layer thickness with increasing temperature exhibit significant differences across the critical point, which we attribute to the influence of critical fluctuations. Furthermore, we argue that the liquid-order phase is more strongly affected by undulation repulsion compared to the liquid-disorder phase, and in the liquid-disorder phase, an additional unknown repulsive force may exist that influences the interactions between membranes. These findings contribute to understanding the role of critical fluctuations in membrane fusion and establish a connection between critical behavior and interbilayer interactions in lipid membranes.
