Nitrogen-detected TROSY yields comparable sensitivity to proton-detected TROSY for non-deuterated, large proteins under physiological salt conditions

Abstract

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.