Mantsch H H, Perczel A, Hollósi M, Fasman G D
Institute for Biodiagnostics, National Research Council of Canada, Winnipeg, Manitoba.
Biopolymers. 1993 Feb;33(2):201-7. doi: 10.1002/bip.360330202.
The beta-turn represents a structural element frequently encountered in globular proteins. However, in spite of various theoretical and experimental studies the ir signature bands of pure beta-turns are still not established beyond doubt. Although considerable information exists now on the ir spectra of alpha-helical and beta-sheet structures, the lack of knowledge concerning turn structures in general, and that of beta-turns in particular, presents a major uncertainty in the estimation of global protein secondary structures from ir spectroscopic data. To obtain more specific information about the characteristic amide bands in beta-turns, we report herein an ir spectroscopic analysis of a series of five cyclic pseudo-hexapeptides known to form beta-turns from previous CD and nmr studies [A. Perczel, M. Hollósi, B. M. Foxman, and G. D. Fasman (1991) Journal of the American Chemical Society, Volume 113, pp. 9772-9784]. We show here that in these cyclic peptides the amide groups involved in beta-turns that comprise a ten-membered hydrogen-bonded ring (and represent the first H-bond pair in a beta-sheet), give rise to characteristic amide I bands in the range 1638-1646 cm-1, with the exact position depending on the solvent and the nature of the side-chain substituents.
β-转角是球状蛋白质中常见的一种结构元件。然而，尽管进行了各种理论和实验研究，但纯β-转角的红外特征谱带仍未完全确定。虽然目前关于α-螺旋和β-折叠结构的红外光谱已有相当多的信息，但总体上对转角结构缺乏了解，尤其是对β-转角缺乏了解，这在从红外光谱数据估计蛋白质整体二级结构时带来了很大的不确定性。为了获得关于β-转角中酰胺特征谱带的更具体信息，我们在此报告了对一系列五个环状拟六肽的红外光谱分析，根据之前的圆二色光谱（CD）和核磁共振（NMR）研究[A. Perczel, M. Hollósi, B. M. Foxman, and G. D. Fasman (1991) Journal of the American Chemical Society, Volume 113, pp. 9772 - 9784]，这些肽已知能形成β-转角。我们在此表明，在这些环状肽中，参与形成包含十元氢键环（且代表β-折叠中的第一对氢键）的β-转角的酰胺基团，会在1638 - 1646 cm⁻¹范围内产生特征性的酰胺I谱带，其确切位置取决于溶剂和侧链取代基的性质。
