Ultrafast energy relaxation dynamics of amide I vibrations coupled with protein-bound water molecules

• Published in: Nature communications 2019-03, Vol.10 (1), p.1010-1010, Article 1010
• Main Authors: Tan, Junjun, Zhang, Jiahui, Li, Chuanzhao, Luo, Yi, Ye, Shuji
• Format: Article
• Language: English
• Subjects: 140/125; 639/638/440/948; 639/638/542/967; 639/638/542/971; Bound water; Coupling (molecular); Dependence; Dynamics; Energy transfer; Exposure; Humanities and Social Sciences; Lipids; multidisciplinary; Proteins; Relaxation time; Science; Science (multidisciplinary); Spectroscopy; Vibrations; Water chemistry
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-08899-3

The influence of hydration water on the vibrational energy relaxation in a protein holds the key to understand ultrafast protein dynamics, but its detection is a major challenge. Here, we report measurements on the ultrafast vibrational dynamics of amide I vibrations of proteins at the lipid membrane/H 2 O interface using femtosecond time-resolved sum frequency generation vibrational spectroscopy. We find that the relaxation time of the amide I mode shows a very strong dependence on the H 2 O exposure, but not on the D 2 O exposure. This observation indicates that the exposure of amide I bond to H 2 O opens up a resonant relaxation channel and facilitates direct resonant vibrational energy transfer from the amide I mode to the H 2 O bending mode. The protein backbone motions can thus be energetically coupled with protein-bound water molecules. Our findings highlight the influence of H 2 O on the ultrafast structure dynamics of proteins. Vibrational energy relaxation of proteins helps us to understand ultrafast protein dynamics. Here, the authors determine the vibrational energy transfer time of the amide I mode in aqueous environment and find that water provides a “shortcut” through a direct resonant channel to dissipate energy into the solvent.