The vibrational coupling between protein backbone modes and the role of water interactions are important topics in biomolecular spectroscopy. Our work reports the first study of the coupling between amide I and amide A modes within peptides and proteins with secondary structure and water contacts. We use two-color two-dimensional infrared (2D IR) spectroscopy and observe cross peaks between amide I and amide A modes. In experiments with peptides with different secondary structures and side chains, we observe that the spectra are sensitive to secondary structure. Water interactions affect the cross peaks, which may be useful as probes for the accessibility of protein sites to hydration water. Moving to two-color 2D IR spectra of proteins, the data demonstrate that the cross peaks integrate the sensitivities of both amide I and amide A spectra and that a two-color detection scheme may be a promising tool for probing secondary structures in proteins.

中文翻译：

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使用双色二维红外光谱探测水合蛋白质内的主链耦合

蛋白质主链模式之间的振动耦合和水相互作用的作用是生物分子光谱学的重要主题。我们的工作报告了首次研究具有二级结构和水接触的肽和蛋白质内酰胺 I 和酰胺 A 模式之间的耦合。我们使用双色二维红外 (2D IR) 光谱并观察酰胺 I 和酰胺 A 模式之间的交叉峰。在具有不同二级结构和侧链的肽的实验中，我们观察到光谱对二级结构敏感。水的相互作用会影响交叉峰，这可用作蛋白质位点与水合水的可及性的探针。转向蛋白质的双色二维红外光谱，数据表明交叉峰整合了酰胺 I 和酰胺 A 光谱的灵敏度，并且双色检测方案可能是探测蛋白质二级结构的有前途的工具。