化学
亚甲基
胺气处理
区域选择性
肽
立体化学
分子内力
氨基酸
鸟氨酸
赖氨酸
肽合成
精氨酸
组合化学
阳离子聚合
生物化学
药物化学
有机化学
催化作用
作者
Bibhas Hazra,Mahesh Prasad,Rajat Roy,Pradip K. Tarafdar
摘要
The proteinogenic lysine (Lys) and arginine (Arg) have multiple methylene groups between α-carbon and the terminal charged centre. Why nature did not select ornithine (Orn), 2,4-diamino butyric acid (Dab) and 2,3-diamino propionic acid (Dpr) with fewer methylene groups in the side chain remains an important question! The propensity of aminoacyl-tRNA (aa-tRNA) model substrates towards self-degradation via intramolecular lactamization was studied using UV spectroscopy and 1H-NMR titration, which showed that Lys and Arg remain stable, and Orn and Dab cyclize to lactam. Hydrophobicity-assisted surface mediated model peptide formation highlighted that the microenvironment and pKa perturbation led to poor regioselectivity (α-amine vs. terminal amine) in Dpr and other non-proteinogenic analogues. The α-selectivity became even poorer in the presence of phosphate, making them ill-suited for peptide synthesis. Superior regioselectivity of the Lys aa-tRNA model substrate suggests that the extra methylene bridge helped nature to separate the microenvironments of the α-amine and ε-amine to synthesize the peptide backbone.
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