從構形、結構分析及圓二色光譜實驗探討α螺旋和β摺板內之靜電荷作用力

Conformational Analysis, Structure Surveys, and Circular Dichroism Spectroscopy Experiments of Intrahelical and Cross-Strand Electrostatic Interactions

王偉任(Wei-Ren Wang)

指導教授 ： 陳平

國立臺灣大學/理學院/化學研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.10814

摘要

蛋白質對於生物功能扮演重要角色， 蛋白質的結構可決定功能． 蛋白質結構穩定度會受到非共價鍵作用力的影響．帶電荷胺基酸可產生靜電作用力來穩定蛋白質結構．利用統計調查以及理論計算來瞭解帶電荷胺基酸對於蛋白質穩定度的影響．並討論不同二級結構中的靜電作用力以及螺旋末端設計產生的作用．利用相關實驗來探討對於螺旋內離子作用力對於螺旋結構的影響．不同側鏈長度的正負電荷電胺基酸產生的螺旋內作用力可以影響螺旋結構．透過了解胺基酸側鏈長度對於作用力以及結構穩定度的影響可以應用於蛋白質藥物研發、工業上生物轉換以及生物感測器的發展．由於精氨酸對於尿素循環以及氮氧化合物產生扮演重要角色，合成出一系列含有穀胺酸或天門冬胺酸以及精氨酸的胜肽(ZbbAgh3, ZbbAgp4, ZbbAgb5, Zbb=Glu or Asp)來探討不同胺基酸側鏈長度以及相對位置對於螺旋結構的影響．利用圓二色光譜儀測量胜肽的螺旋程度探討不同酸鹼程度條件下螺旋內的離子配對作用力．結果顯示Asp-Agp (i,i+4)以及Asp-Agb (i,i+5)　離子配對作用力大於Glu-Agp (i,i+4) and Glu-Agb (i,i+5)的作用力．

關鍵字

α-螺旋 ； 精氨酸 ； 螺旋末端 ； 螺旋傾向 ； 離子對 ； 離氨酸 ； 蛋白質

並列摘要

Protein is the most abundant biopolymer that partakes in nearly all biological functions. Importantly, the characteristic behavior of a protein is determined by its structure. Furthermore, the non-covalent driving forces of protein folding into a well defined structure are the origin of protein structure stability. Electrostatics is one of the key forces to stabilize protein structures, involving charged amino acids. To further understand the contribution of charged amino acids to protein stability, a series of surveys on protein structures and theoretical calculations were performed. In particular, electrostatic interactions in different secondary structures and helix capping effects are discussed. Further experiments were performed to understand the intrahelical ion pairing interaction. Intrahelical interaction between positively charged amino acids (Arg or Lys) and negatively charged amino acids (Asp or Glu) can exert a stabilizing or destabilizing effect on helices. Interestingly, these amino acids have different side chain lengths. Understanding how the side chain length reigns the interactions and structures might benefit protein-related applications, such as protein therapeutics, industrial scale biotransformations, and biosensors. As Arg is a vital component in the urea cycle and nitric oxide generation, peptides (ZbbAgh3, ZbbAgp4, ZbbAgb5, Zbb=Glu or Asp) containing Glu/Asp and Arg analogues with different side chain length and spacing were synthesized to research the effect of side chain length. The helical content of the peptides were measured by circular dichroism spectroscopy to investigate the effect on ion pairing interactions at different pH values. The results suggest that both Asp-Agp (i,i+4) and Asp-Agb (i,i+5) ion pairing interaction may be stronger than Glu-Agp (i,i+4) and Glu-Agb (i,i+5).

並列關鍵字

α-helix ； arginine ； helix capping ； helix propensity ； ion pair ； lysine ； protein.

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