Conformational study of some component peptides of pentagastrin

Conformational study of some component peptides of pentagastrin
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五肽胃泌素部分成分肽的构象研究

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发表时间：
1972
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通讯作者：
H. Gregory
H. Gregory
中科院分区：
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文献类型：
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作者：
J. Feeney;G. Roberts;J. P. Brown;A. Burgen;H. Gregory

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质子核磁共振在水溶液和二甲基亚砜溶液中研究了 Asp、Phe、Asp-Phe-NH2、Met-Asp-Phe-NH2、Trp-Met-Asp-Phe-NH2 和 Boc-βAla-Trp-Met-Asp-Phe-NH2 的光谱。通过分析 Asp 和 Phe C(α)H·C(β)H2 侧链的 1H 光谱，获得邻位耦合常数并用于计算旋转种群。三肽 Met-Asp-Phe-NH2 和胃泌素五肽 βAla-Trp-Met-Asp-Phe-NH2 之间的 Phe 侧链旋转异构体群没有显着差异，但 Asp 残基显示出一些小的变化。Trp 中芳环对 Phe 芳香质子仅存在较小的环电流屏蔽贡献，可以表明芳环在 Trp 中分离良好（>5 A）。胃泌素五肽在水溶液中最多的构象异构体。对于二甲基亚砜溶液，可以在所研究的肽中观察到 NH 双峰；四肽 Trp-Met-Asp-Phe-NH2 中 Met、Asp 和 Phe 的邻位 JNC 耦合常数的大值与最密集的构象一致，具有 ca 角。 –95°，考虑到势能图和 Bystrov 修改的 Karplus 曲线，该曲线将二面角与邻位耦合常数联系起来。
The proton n.m.r. spectra of Asp, Phe, Asp-Phe-NH2, Met-Asp-Phe-NH2, Trp-Met-Asp-Phe-NH2, and Boc-βAla-Trp-Met-Asp-Phe-NH2 have been studied in aqueous and dimethyl sulphoxide solutions. From an analysis of the 1H spectra of the Asp and Phe C(α)H·C(β)H2 side-chains the vicinal coupling constants were obtained and used to calculate the rotational populations. There are no significant differences in the Phe side-chain rotamer populations between the tripeptide Met-Asp-Phe-NH2 and gastrin pentapeptide βAla-Trp-Met-Asp-Phe-NH2, but the Asp residue shows some small changes.The presence of only small ring-current shielding contributions to the Phe aromatic protons from the aromatic ring in Trp can be taken to indicate that the aromatic rings are well separated (>5 A) in the most populated conformers of gastrin pentapeptide in aqueous solution.For dimethyl sulphoxide solutions, NH doublets could be observed for the peptides studied; the large values of the vicinal JNC coupling constants for Met, Asp, and Phe in the tetrapeptide Trp-Met-Asp-Phe-NH2 are shown to be consistent with the most populated conformations, having a ϕ angle of ca. –95°, from considerations of potential energy diagrams and the Bystrov-modified Karplus curve which relates dihedral angles to vicinal coupling constants.