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Updated: Mar 7, 2026

Methods to Identify the NMR Resonances of the 13C-Dimethyl N-terminal Amine on Reductively Methylated Proteins
Published on: December 12, 2013
An Integrated Approach to Unique NMR Assignment of Methionine Methyl Resonances in Proteins
Fei Yu1, Jing Qiao1, John Robblee1
1Momenta Pharmaceuticals Inc. , 675 West Kendall Street, Cambridge, Massachusetts 02142, United States.
Abstract:
The application of methyl nuclear magnetic resonance (NMR) spectroscopy in protein side-chain structural studies offers unique advantages of greater peak sensitivity, even for high-molecular-weight proteins. Traditionally, the utility of methyl NMR has often been limited by the difficulty in assigning the methyl resonances. Herein, a mass spectrometry (MS)-assisted strategy to assign the methyl resonances of methionine residues is presented. The strategy involves partially oxidizing the methionine and quantifying the oxidation level by both NMR and liquid chromatography-mass spectrometry (LC-MS). The NMR assignment of methyl resonances of methionine is made by correlating the quantitative results obtained from both NMR and MS. The method has been successfully demonstrated using the proteins hen egg-white lysozyme (HEWL) and porcine pepsin. The technique described herein can help facilitate the application of methyl NMR as a useful tool to study protein structure, dynamics, and interactions.
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