An Optimized Relaxation-Based Coherence Transfer NMR Experiment for the Measurement of Side-Chain Order in Methyl-Protonated, Highly Deuterated Proteins

• Published in: The journal of physical chemistry. B Vol. 115; no. 49; pp. 14878 - 14884
• Main Authors: Sun, Hechao, Kay, Lewis E, Tugarinov, Vitali
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 15.12.2011
• Subjects: B: Biophysical Chemistry; Carbon Isotopes - chemistry; Coherence; Deuteration; Deuterium - chemistry; Gain; Magnetization; Monitors; NMR spectroscopy; Nuclear Magnetic Resonance, Biomolecular; Proteins; Proteins - chemistry; Protons; Quantum Theory; Utilities
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp209049k

Relaxation violated coherence transfer NMR spectroscopy has emerged as a powerful experimental tool for the quantitative measurement of amplitudes of motion of methyl containing side-chains. Typically, the experiments, performed on proteins that are highly deuterated and methyl-protonated, monitor the build-up of methyl 1H double-quantum magnetization. Because all three protons in a methyl group are degenerate, such coherences can only result from differential relaxation of transverse magnetization components, which in turn reflect the extent and time-scale of motion of the methyl probe [Tugarinov, V., Sprangers, R.; Kay, L.E. J. Am. Chem. Soc. 2007, 129, 1743–1750]. We show here that a 50% gain in the sensitivity of the experiment can be achieved through selection of 1H triple-quantum coherence, thereby significantly increasing the utility of the approach. A theoretical treatment rationalizes the sensitivity gain that is subsequently verified through experiment. The utility of the methodology is demonstrated on a number of proteins, including the 360 kDa α7α7 “half-proteasome”.