研究人員發現到膜蛋白與膽固醇並非均勻分布於細胞膜，而是形成異質性結構。特定膜蛋白與膽固醇集結的區塊被稱作脂筏。鑒於目前的技術尚無法直接在細胞膜上觀測到脂筏，脂筏的形成機制仍屬未知。脂筏得以透過相分離形成是當前的主流觀點之一，但由細胞膜分離出來的仿生物膜卻無法在人體溫度下發生相分離行為。臨界現象為脂筏的形成機制開闢了新的方向。只有當系統非常接近臨界點時才會發生臨界漲落。臨界漲落會使局部的組成出現消長並形成存在時間極短的動態區塊。近期一份研究指出，相分離形成的區塊邊界對HIV病毒的膜融合有顯著影響。本研究將探討臨界漲落產生的動態區塊，即使存在時間非常短，是否同樣能促進膜融合。本實驗分別利用螢光光譜儀與小角度X光散射儀量測膜融合與脂雙層膜的結構。我們致力於發掘臨界漲落如何影響到生物膜結構，從而改變生成膜融合中間態所需的能量。膜融合中間態是掌握膜融合能否完成的關鍵。我們期待針對臨界漲落與膜融合的研究成果，能為對抗冠狀病毒提供新穎的見解。;Researchers have found that cell membranes are heterogeneous, in the sense that membrane proteins and cholesterol tend to segregate and be unevenly distributed within cell membranes. Domains arising from the segregation is known as lipid rafts. The exact mechanisms for raft formation remains a debate due to the lack of direct observations of rafts in cell membranes. While phase separation observed in model membranes is one of the leading explanations for raft formation, no phase separation can be observed at physiological temperatures on the giant plasma membrane vesicles directly derived from cellular plasma membranes. Hence, critical fluctuation emerges as an alternative explanation for rafts. Critical fluctuation arises only when homogeneous membrane is extremely close to the critical point. At this point, it shows fluctuations in local composition and transiently forms segregation domains. A recent research found that phase separation, which spawns line tension on domain boundaries, had a significant effect on membrane fusion for HIV virus. In this thesis work, we explore whether critical fluctuation also facilitates membrane fusion even though it only transiently forms domains. Fluorescent spectroscopy and small angle X ray scattering are employed to measure the membrane fusion efficiency and membrane structure, respectively. We aim to understand how critical fluctuation modulates the membrane structure and thereby varies the energy barriers for forming fusion intermediate structures, which in turn dictates the fusion efficacy. The results are expected to have broad implications for the fights against the membrane-bound coronavirus.
