中文摘要
　　由於越來越多的致病原對抗生素具有抗藥性，所以發展新的抗菌分子則越發顯得重要；而抗菌胜肽則是重要的焦點之一；抗菌胜肽廣布在自然界之生物體中，為最早發展出來的先天性免疫系統。絕大部分的抗菌胜肽可以快速專一地殺掉目標細胞，而且其作用物種很廣泛。抗菌胜肽除了具有抗微生物的功能外，還具有其他功能，像是促進傷口癒合，刺激單核球的趨化反應，及抑制細胞激素cytokine的反應。了解這些胜肽的結構可以幫助更加了解其功能。
　　Parasin I原始的前趨物是鯰魚的histone H2A，胺基酸序列為Lys-Gly-Arg-Gly-Lys-Gln-Gly-Gly-Lys-Val-Arg-Ala-Lys-Ala-Lys-Thr-Arg-Ser-Ser。
　　本論文利用氫原子核磁共振光譜，在SDS仿細菌膜環境下研究其三度空間的結構。在計算得到parasin I的結構後，發現雖然parasin I沒有一般常見的二級結構的組成存在。但是，可以看出琪具有兩性結構，殘基10、12、14的胺基酸組成疏水性團，而殘基11、13、15組成親水性團。由parasin I在微泡中之結構，可以推斷parasin I作用機轉可能是以靜電作用力為主。

　With the rise of pathogens resistant to conventional antibiotics, the search for novel antimicrobial agents has heightened. Antimicrobial peptides have been one area of great focus. The structural features of these peptides give insight into how they functions. Parasin I is an antimicrobial peptide derived from histone H2A in the catfish, Parasilurus asotus. The complete amino acid sequence of parasin I, which was determined by automated Edman degradation, was Lys-Gly-Arg-Gly- Lys-Gln-Gly-Gly-Lys-Val-Arg-Ala-Lys-Ala-Lys-Thr-Arg-Ser-Ser.
　Its structure in SDS micelle was determined using proton NMR data. Solution structure of parasin I lacks classical secondary structures in SDS micelle when pH is 5.0. Residues Val10, Ala12, and Ala14 were located at the hydrophobic side of the structure and Arg11, Lys13, and Lys15 were located at the polar side. Electrostatic interactions may play an important role in the binding of this peptide to the membrane surface.

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