Fast access to protein dynamics using Hartmann-Hahn edited 15N- 1H spectroscopy
Résumé
Introduction: Spectral congestion in protein NMR spectra is a never disappearing problem. Typically, this issue is solved by increasing the number of increments in the indirect dimension or dimensionality of experiments. This procedure is, however, bound by increase of acquisition times of spectra leading to greater costs of NMR experiments recorded, challenging their improvement. Especially for relaxation experiments, where sufficient sampling is required, or for zz-exchange experiments, where additional exchange cross peaks are present, this becomes an important limitation. Aim: To reduce experimental time, an alternative approach is to use selective experiments that target particular 1H-15N correlations, allowing the use of simple 1D experiments. Selective Hartmann- Hahn coherence transfer has been previously proposed for this purpose (1, 2), but the selectivity of these experiments was limited. Here, we propose a scheme that provides clean 1D spectra with an improved selectivity of 15–20 Hz in 15N with only a modest cost in sensitivity. Results: Our approach combines an alternative and, to the best of our knowledge, neglected scheme for selective cross-polarization combined with an improved zeta-purge element (1, 3). We will show how our experiment allows to resolve otherwise overlapped in other approaches cross and diagonal peaks within a zz-exchange experiment, allowing to access the information on exchange in a fraction of the time required using non-selective (pseudo-3D) experiments (4). Conclusions: The new experiment provides sufficiently selective and clean spectra to resolve information in acceptable measurement times, and will be very valuable for studying the dynamics of proteins featuring heavily congested spectra. References: 1. D. Korzhnev et al., J. Am. Chem. Soc. 127, 713-721 (2005) 2. M. Nishizawa et al., J. Biomol. NMR 74, 205–211 (2020) 3. P. Pelupessy et al., Conc. Magn. Reson. 12, 103–124 (2000) 4. N. A. Farrow et al., J. Biomol. NMR 4, 727–734 (1994)