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研究生: 楊淑芬
論文名稱: 心臟毒蛋白之分子動力學模擬
Molecular Dynamics Simulation of Cardiotoxins
指導教授: 孫英傑
學位類別: 碩士
Master
系所名稱: 化學系
Department of Chemistry
畢業學年度: 86
語文別: 中文
論文頁數: 94
中文關鍵詞: 毒蛋白動力學
論文種類: 學術論文
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  • 臺灣眼鏡蛇毒液心臟毒蛋白是全為β摺板的小蛋白質分子,包含60~62個胺基酸殘基,五個α股,前兩股與後三股各組成β摺板,並有四個雙硫鍵連接分子骨架。我們運用分子動力學模擬檢視其在水溶液中的結構與運動性。根據Lipari-Szabo model-free理論所計算得到的蛋白質Cα-H鍵秩序參數值與NMR實驗結果的比較,可以檢視理論計算模型的再現性,所計算的蛋白質骨架原子的β因子值,也同時與晶體結構資料比較。我們由分子結構的構形和蛋白質殘基之間的作用力,討論目前的模擬結果和實驗結果之間的異同,及其動力學性質。
    理論計算值整體上與實驗結果在定性上一致,多個胺基酸在定量上也相當吻合。在蛋白質CTX II分子的MD模擬結構顯示,分子βl-loopl-β2區域與NMR結構有明顯的結構偏差;CTX II和CTX III分子在三個環圈部位的骨架擾動性比分子的其他部位來得大,由CTX II與CTX III的次ns軌跡所得到的秩序參數值結果顯示,CTX II分子的loppl和loop3區域的結構擾動比CTX III分子來的小,但是在loop2處的運動性則比CTX III分子大。

    Cardiotoxins from venom of Taiwan Cobra, Naja naja atra, are small 5-β strand and 3-loop basic proteins of 60~62 residues cross-linked by four disulfide bridges.
    Molecular dynamics simulation was carried out to examine backbone mobility of CTX II in solution and aid in interpretation of order parameters of Cα-H bonds obtained from NMR experiments based on Lipari-Szabo theory. The Calculated order parameters of C□-H bonds and B-factors of CTX II in solution were compared with NMR-derived backbone order parameters and crystal structure data, respectively. Overall qualitative agreement was obtained whereas the calculated values and experimental results of many residues are in good agreement quantitatively. The discrepancies between the present computed results and experiments values, physical basis, and plausible biological function are discussed.
    Derivation in structure of CTX II in MD simulation from NMR structure occurs at loops, particularly at loop1. From the present subnano second molecular dynamics trajectories of CTX II and CTX III, the calculated order parameters show that, at loop1 and loop3 segments, the structural fluctuation of CTX II is smaller than CTX III but larger than CTX III at loop2.

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