Precision measurements of relaxation rates of degenerate <superscript>1</superscript> H transitions in methyl groups of small proteins.

An NMR experiment is designed for accurate and robust measurement of transverse relaxation rates of degenerate 1 H transitions in selectively 13 CH 3 -labeled, deuterated small proteins. The measurement is based on the use of acute (<90°) angle 1 H radio-frequency pulses and relies on selection of the slow- and fast-relaxing components of methyl magnetization following the relaxation period in separate experiments. The R 2 decay series recorded with selection of the fast-relaxing components serves as a useful complement to the R 2 series acquired with selection of the slow-relaxing part, and permits the extension of the range of relative contributions of the fast- and slow-relaxing parts to apparent signal decay. The approach is experimentally verified on 13 CH 3 methyl groups of the ILV-{ 13 CH 3 }-labeled protein ubiquitin at 10 °C and 25 °C. The obtained methyl 1 H relaxation rates are in remarkably good agreement with the values obtained from well-established NMR techniques.

Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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