本論文主要研究混合界面活性劑Triton X-100和雙電性脂質二棕櫚醯磷脂醯膽鹼(DPPC)形成的圓盤形微胞，並研究攙入帶正電荷的脂質DOTAP和DC-Cholesterol的影響。電荷比例固定在 15 %及30 %，及固定總共長鏈脂質分子的莫耳濃度10 mM，研究混合不同莫耳數比例的Triton X-100，[Triton X-100]/[Lipid] = 0, 0.33, 0.66, 1, 2, 3, 4, 5, 7.5, 10，在水溶液中所形成的混合聚集結構。研究發現要大約加入1:1以上的Triton X-100才可以將所有的DPPC轉變成圓盤形微胞，比用diC7PC的0.25:1要高許多。利用小角度散射方法進行臨場變溫的實驗，量測其結構變化。並利用帶正電荷的混合圓盤形微胞加入DNA，形成複合聚集成多層圓盤堆疊結構，DNA則包夾在層與層的圓盤形微胞中間。從小角度X光散射量測數據，經擬合分析可以得到圓盤形微胞在1:1、1:1.5、1:2和1:3的結構變化，加入越多的Triton X-100會使圓盤形微胞的直徑從1:1時的102 Å，變成1:1.5時的72 Å，1:2時的63 Å，及1:3時的60 Å，會逐漸變小。由穿透式電子顯微鏡可觀察確認圓盤形微胞的存在。加入DOTAP或DC-Cholesterol只稍微影響圓盤微胞的大小，從小角度X光散射圖可觀察到加入DNA時會產生由多層堆疊結構造成的繞射峰。當升溫至超過DPPC長鏈的熔點溫度，Triton X-100/DPPC的圓盤微胞亦會融接成大的片狀結構，但沒有繞射峰，表示不會堆疊黏在一起，和diC7PC/DPPC的圓盤微胞不同。若是使用Ibuprofen代替Triton X-100則無法形成圓盤微胞。

In this thesis, the aggregation structure of mixing DPPC with Triton-X100 was investigated by Small-Angle X-ray Scattering (SAXS) and TEM. Typically, disc-shaped bicelle can be formed by mixing the short-chain lipid with long-chain lipid at ratios of about 0.2 to 1. Other than using the short-chain lipids, it has also been found that using Triton X-100 may also form disc-shaped bicelles with DPPC. The incorporation of cationic lipid DOTAP and DC-Cholesterol in the mixed Triton X-100 and DPPC bicelle was also investigated. It was found that disc-shaped bicelle can be formed at Triton X-100 to DPPC molar ratio from about 1 to 3. As determined from SAXS, the diameter of the disc bicelle decreases from 102 Å at 1: 1 to 72 Å at 1: 1.5, 63 Å at 1: 2, and 60 Å at 1: 3 (DPPC to Triton X-100 molar ratio). The formation of the disc-shaped bicelle was also confirmed by TEM. The addition of DOTAP or DC-Cholesterol only slightly affects the size of the bicelles. Adding DNA into the cationic DPPC/Triton X-100 bicelle induces the formation of stacking multilamellar aggregation structure. The anionic DNA molecules were encapsulated between the cationic bilayers. When the DPPC/Triton X-100 bicelles are heated above the long-chain melting temperature, the bicelles are found to fuse into large sheets but they do not form multilamellar structure, which is different from the DPPC/diC7PC bicelles. It is likely that the long hydrophilic head group of the Triton-X100 could impede the formation of the multilamellar structure when the Triton X-100 molecules are solubilized into the DPPC bilayer at above the DPPC chain melting temperature.

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