Protein in-cell NMR spectroscopy at 1.2 GHz

In-cell NMR spectroscopy provides precious structural and functional information on biological macromolecules in their native cellular environment at atomic resolution. However, the intrinsic low sensitivity of NMR imposes a big limitation in the applicability of the methodology. In this respect, the recently developed commercial 1.2GHz NMR spectrometer is expected to introduce significant benefits. However, cell samples may suffer from detrimental effects at ultrahigh fields, that must be carefully evaluated. Here we show the first in-cell NMR spectra recorded at 1.2GHz on human cells, and we compare resolution and sensitivity against those obtained at 900 and 950MHz. To evaluate the effects of different spin relaxation rates, SOFAST-HMQC and BEST-TROSY spectra were recorded on intracellular alpha-synuclein and carbonic anhydrase. Major improvements are observed at 1.2GHz when analyzing unfolded proteins, such as alpha-synuclein, while the TROSY scheme improves the resolution for both globular and unfolded proteins.