Amide I′-II′ 2D IR Spectroscopy Provides Enhanced Protein Secondary Structural Sensitivity
Amide I′-II′ 2D IR Spectroscopy Provides Enhanced Protein Secondary Structural Sensitivity
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DOI：
10.1021/ja8094922
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发表时间：
2009-03-11
影响因子：
15
通讯作者：
Tokmakoff, Andrei
中科院分区：
文献类型：
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作者：
DeFlores, Lauren P.;Ganim, Ziad;Tokmakoff, Andrei
我们演示了如何多模二维红外光谱的蛋白质酰胺I'和II'的振动可以用来区分蛋白质的二级结构。对β-折叠、α-螺旋和无规卷曲构象中的聚-L-赖氨酸进行的偏振依赖性酰胺I '-II' 2D IR实验表明，酰胺I'和II'对角峰和交叉峰的组合可以有效区分二级结构含量，而酰胺I'红外光谱单独不能区分二级结构含量。增强的灵敏度源于酰胺II'和酰胺I'光谱之间的频率和振幅相关性，其反映了二级结构的对称性。2D IR表面用于参数化适合于预测蛋白质酰胺I '-II'光谱的酰胺I '-II'歧管的激子模型。该模型表明，占主导地位的振动相互作用，有助于这种敏感性是一个组合的负酰胺II '-II'通过键耦合和酰胺I '-II'耦合内的肽单元。经验确定的酰胺II '-II'偶联不随二级结构显著变化：β折叠为-8.5 cm（-1），α折叠为-8.7 cm（-1）。螺旋，和-5厘米（-1）的线圈。
We demonstrate how multimode 2D IR spectroscopy of the protein amide I' and II' vibrations can be used to distinguish protein secondary structure. Polarization-dependent amide I'-II' 2D IR experiments on poly-L-lysine in the beta-sheet, alpha-helix, and random coil conformations show that a combination of amide I' and II' diagonal and cross peaks can effectively distinguish between secondary structural content, where amide I' infrared spectroscopy alone cannot. The enhanced sensitivity arises from frequency and amplitude correlations between amide II' and amide I' spectra that reflect the symmetry of secondary structures. 2D IR surfaces are used to parametrize an excitonic model for the amide I'-II' manifold suitable to predict protein amide I'-II' spectra. This model reveals that the dominant vibrational interaction contributing to this sensitivity is a combination of negative amide II'-II' through-bond coupling and amide I'-II' coupling within the peptide unit. The empirically determined amide II'-II' couplings do not significantly vary with secondary structure: -8.5 cm(-1) for the beta sheet, -8.7 cm(-1) for the a. helix, and -5 cm(-1) for the coil.