Nitrogen-detected TROSY yields comparable sensitivity to proton-detected TROSY for non-deuterated, large proteins under physiological salt conditions
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Direct detection of the TROSY component of proton-attached 15N nuclei (15N-detected TROSY) yields high quality spectra with high field magnets, by taking advantage of the slow 15N transverse relaxation. The slow transverse relaxation and narrow line width of the 15N-detected TROSY resonances are expected to compensate for the inherently low 15N sensitivity. However, the sensitivity of 15N-detected TROSY in a previous report was one-order of magnitude lower than in the conventional 1H-detected version. This could be due to the fact that the previous experiments were performed at low salt (0–50 mM), which is advantageous for 1H-detected experiments. Here, we show that the sensitivity gap between 15N and 1H becomes marginal for a non-deuterated, large protein (τ c = 35 ns) at a physiological salt concentration (200 mM). This effect is due to the high salt tolerance of the 15N-detected TROSY. Together with the previously reported benefits of the 15N-detected TROSY, our results provide further support for the significance of this experiment for structural studies of macromolecules when using high field magnets near and above 1 GHz.
KeywordsNitrogen detection TROSY High field magnet Protein NMR Salt concentration Sensitivity
This work was supported by METI (Grant name: development of core technologies for innovative drug development based upon IT) to I.S. and by NIH Grants GM047467 and AI 37581 to G.W. This work was also partly supported by JST, PRESTO to K.T. Maintenance of NMR instruments was supported in part by NIH Grant EB002026.
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