Isotope-Edited Amide II Mode: A New Label for Site-Specific Vibrational Spectroscopy
- 13 July 2021
- journal article
- research article
- Published by American Chemical Society (ACS) in The Journal of Physical Chemistry Letters
- Vol. 12 (28), 6634-6638
- https://doi.org/10.1021/acs.jpclett.1c01073
Abstract
Vibrational spectroscopy is a powerful tool used to analyze biological and chemical samples. However, in proteins, the most predominant peaks that arise from the backbone amide groups overlap one another, hampering site-specific analyses. Isotope editing has provided a robust, noninvasive approach to overcome this hurdle. In particular, the 1-13C═16O and 1-13C═18O labels that shift the amide I vibrational mode have enabled 1D- and 2D-IR spectroscopy to characterize proteins with excellent site-specific resolution. Herein, we expand the vibrational spectroscopy toolkit appreciably by introducing the 1-13C 15N probe at specific locations along the protein backbone. A new, isotopically edited amide II peak is observed clearly in the spectra despite the presence of unlabeled modes arising from the rest of the protein. The experimentally determined shift of −30 cm–1 is reproduced by DFT calculations providing further credence to the mode assignment. Since the amide II mode arises from different elements than the amide I mode, it affords molecular insights that are both distinct and complementary. Moreover, multiple labeling schemes may be used simultaneously, enhancing vibrational spectroscopy’s ability to provide detailed molecular insights.Funding Information
- Israel Science Foundation (175/13, 948/19)
- United States - Israel Binational Science Foundation (2013618)
- Ministry of Science and Technology, Israel (66257)
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