The diagonal anharmonicity of an amide I mode of protein backbones plays a critical role in a protein’s vibrational dynamics and energy transfer. However, this anharmonicity of long-chain peptides and proteins in H2O environment is still lacking. Here, we investigate the anharmonicity of the amide I band of proteins at the lipid membrane/H2O interface using a surface-sensitive pump–probe setup in which a femtosecond infrared pump is followed by a femtosecond broadband sum frequency generation vibrational spectroscopy probe. It is found that the anharmonicity of the amide I mode in ideal α-helical and β-sheet structures at hydrophobic environments is 3–4 cm−1, indicating that the amide I mode in ideal α-helical and β-sheet structures is delocalized over eight peptide bonds. The anharmonicity increases as the bandwidth of the amide I mode increases due to the exposure of peptide bonds to H2O. More H2O exposure amounts lead to a larger anharmonicity. The amide I mode of the peptides with large H2O exposure amounts is localized in one to two peptide bonds. Our finding reveals that the coupling between the amide I mode and the H2O bending mode does not facilitate the delocalization of the amide I mode along the peptide chain, highlighting the impact of H2O on energy transfer and structural dynamics of proteins.
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14 March 2022
Research Article|
March 08 2022
Protein–water coupling tunes the anharmonicity of amide I modes in the interfacial membrane-bound proteins
Special Collection:
Time-resolved Vibrational Spectroscopy
Junjun Tan;
Junjun Tan
a)
Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China
, Hefei, Anhui 230026, China
a)Authors to whom correspondence should be addressed: jjtan@ustc.edu.cn and shujiye@ustc.edu.cn. Tel.: 086-551-63603462
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Zijian Ni;
Zijian Ni
Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China
, Hefei, Anhui 230026, China
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Shuji Ye
Shuji Ye
a)
Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China
, Hefei, Anhui 230026, China
a)Authors to whom correspondence should be addressed: jjtan@ustc.edu.cn and shujiye@ustc.edu.cn. Tel.: 086-551-63603462
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a)Authors to whom correspondence should be addressed: jjtan@ustc.edu.cn and shujiye@ustc.edu.cn. Tel.: 086-551-63603462
Note: This paper is part of the JCP Special Topic on Time-Resolved Vibrational Spectroscopy.
J. Chem. Phys. 156, 105103 (2022)
Article history
Received:
November 14 2021
Accepted:
February 17 2022
Citation
Junjun Tan, Zijian Ni, Shuji Ye; Protein–water coupling tunes the anharmonicity of amide I modes in the interfacial membrane-bound proteins. J. Chem. Phys. 14 March 2022; 156 (10): 105103. https://doi.org/10.1063/5.0078632
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