膠原蛋白為人體內含量最豐富的蛋白質，因具良好生物相容性與可降解性等優點，近年來被廣泛應用於生醫材料、醫學等用途。膠原蛋白為三股第二型聚脯胺酸結構鏈所纏繞而成的三股螺旋，依組成可分為同源與異源三股螺旋，而異源三股螺旋又可細分為AAB及ABC型兩類。因人體中含量最多的膠原蛋白為AAB型異源三股螺旋，故探討異源三股螺旋結構穩定性與及相關性質有其重要性。Cation-π作用力為生物體蛋白質中常見之穩定作用力之一，是陽離子與π電流系統間所產生的作用力，實驗室先前的研究也證實此作用力能顯著賦予及提升膠原蛋白三股螺旋穩定度。
本研究以(POG)9胜肽鏈做為基底，藉置換帶正電的Arg及含芳香環側鏈的Tyr於序列中，探討不同位向cation-π作用力對於形成同源與異源三股螺旋之貢獻度。第一部分探討置換Arg與Tyr於胜肽不同位置及有無引入cation-π作用力對三股螺旋穩定度的影響，實驗結果顯示cation-π作用力雖能誘導同源三股螺旋的生成，其穩定度高低和作用力於空間中的位向與指向有關；而未引入cation-π作用力之對照組結果顯示胺基酸置換位置會顯著影響三股螺旋穩定度。
第二部分探討引入股與股間cation-π作用力於胜肽末端是否能有效協助AAB型異源三股螺旋生成。實驗結果顯示各胜肽混合系統皆有異源三股螺旋形成，且三股螺旋穩定度與cation-π作用力強度和位於三股螺旋中的位置有密切相關。上述的實驗結果皆顯示cation-π作用力對於同源與異源三股螺旋形成有重要的貢獻。

Collagen has been widely applied to drug delivery and biological related fields owing to its high biocompatibility, low cytotoxicity and so on. Collagen is comprised of three polyproline II chains, which can be classified to homotrimers or heterotrimers by its composition. It is highly important to study the stability and related properties of heterotrimers because type I collagen(AAB type) is the most abundant collagen in the human body. Cation-π interaction is one of the common stabilizing interactions in proteins, it is the noncovalent force between a positive charge and the aromatic π-system. From the previous studies in our lab, cation-π interaction and the relative position of cationic-aromatic pair were shown to affect the stability of collagen triple helix. In this study, we designed a series of synthetic collagen mimetic peptides (CMPs) containing cationic (Arg) and aromatic (Tyr) residues based on the peptide (POG)9 to explore whether the introduced multiple cation-π interactions can stabilize collagen and induce the folding of collagen heterotrimers. In the first part, the results showed that although the introduced cation-π interactions can stabilize the formation of homotrimers, the stabilization effect is correlated with the location and orientation of cation-π pairs. In the second part, we managed to form the AAB type heterotrimers by making use of the cation-π interactions among the peptide strands. Results of all the peptide mixture systems demonstrate the formation of AAB type heterotrimers, and their stability is affected by the orientation and position of cation-π pairs in the triple helix. The results all above imply that cation-π interactions can be used to effectively stabilize the collagen triple helix and induce the formation of heterotrimers as well.

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