The effects of chain length and thermal denaturation on helix-forming peptides: A mode-specific analysis using 2D FT-IR
The effects of chain length and thermal denaturation on helix-forming peptides: A mode-specific analysis using 2D FT-IR
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DOI：
10.1021/ja970512m
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发表时间：
1997-11-19
影响因子：
15
通讯作者：
Prendergast, FG
中科院分区：
文献类型：
--
作者：
Graff, DK;PastranaRios, B;Prendergast, FG
该项目的主要目标是使用FT-IR光谱监测链长和温度对水溶液中一般形式Ac-W（EAAAR）（n）A-NH 2（其中n = 1、3、5和7）的小的螺旋形成肽的影响。在D2 O中收集FT-IR光谱，作为-4至95 ℃范围内的温度的函数。感兴趣的光谱范围，1500-1725 cm（-1），包含完全交换的H-->D肽键的酰胺-I '带。即使在这些简单的肽中，IR光谱的酰胺-I '区域也是复杂和拥挤的，由来自肽骨架的构象和来自氨基酸侧链的贡献的特征组成。因此，峰位置和强度的非生物学分辨率是极其困难的，特别是在评估两个数据集之间的细微差异时。二维相关分析（Noda，I. J. Am. 1989，111，8116中所述。野田岛应用光谱学1990，44，550）用于指导和验证峰拟合过程的结果，从而促进温度依赖性光谱的物理解释。二维分析和拟合过程的结果表明，光谱带，特别是那些酰胺-I '带，表现出显着的频率偏移和带宽和强度的变化作为温度和链长的函数。对于酰胺-I '模式所产生的螺旋和随机构象的肽键，峰强度的归一化摩尔吸光系数的单位进行了讨论，在不同的模型。两种不同的摩尔吸光系数的计算，第一个使用的长度依赖的α-螺旋频率预测微扰理论，和第二个假设一个更严格的两个状态过渡。从每个的结果进行了讨论的影响链长度对α-螺旋稳定和螺旋展开的机制。
The major goal of this project was to use FT-IR spectroscopy to monitor the effects of chain length and temperature on small, helix-forming peptides of the general form, Ac-W(EAAAR)(n)A-NH2, where n = 1, 3, 5, and 7, in aqueous solutions. FT-IR spectra were collected in D2O as a function of temperature in the range of -4 to 95 degrees C. The spectral range of interest, 1500-1725 cm(-1), contains the amide-I' band of the fully-exchanged H-->D peptide bond. Even in these simple peptides, the amide-I' region of the IR spectra is complex and congested, composed of features derived from the conformation of the peptide backbone and from the contributions of amino acid side chains. Unambiguous resolution of peak positions and intensities is thus extremely difficult, particularly when assessing subtle differences between two data sets. Two-dimensional correlation analysis (Noda, I. J. Am. Chem. Soc. 1989, 111, 8116. Noda, I. Applied Spectrosc. 1990, 44, 550) was used to guide and verify the results of the peak-fitting procedure and thereby facilitate physical interpretation of the temperature-dependent spectra. The results of the two-dimensional analysis and fitting procedure show that the spectral bands, particularly those of the amide-I' band, exhibit significant frequency shifts and bandwidth and intensity changes as a function of temperature and chain length. For the amide-I' modes arising from the helical and random conformations of the peptide bond, the normalization of peak intensities to units of molar absorptivity is discussed in terms of different models. Two different molar absorptivity calculations are presented, the first using the length-dependence of alpha-helical frequencies as predicted by perturbation theory, and the second assuming a more rigorous two-state transition. The results from each are discussed in terms of the effects of chain length on alpha-helix stabilization and in terms of a mechanism of helix unfolding.