Sensitivity Enhancement in 13C Solid-State NMR of Protein Microcrystals by Use of Paramagnetic Metal Ions for Optimizing 1H T1 Relaxation

摘要

We discuss a simple approach to enhance sensitivity for ¹³C high-resolution solid-state NMR for proteins in microcrystals by reducing ¹H T1 relaxation times with paramagnetic relaxation reagents. It was shown that ¹H T1 values can be reduced from 0.4-0.8 s to 60-70 ms for ubiquitin and lysozyme in D2O in the presence of 10 mM Cu(II)Na2EDTA without substantial degradation of the resolution in ¹³C CPMAS spectra. Faster signal accumulation using the shorter ¹H T1 attained by paramagnetic doping provided sensitivity enhancements of 1.4-2.9 for these proteins, reducing the experimental time for a given signal-to-noise ratio by a factor of 2.0-8.4. This approach presented here is likely to be applicable to various other proteins in order to enhance sensitivity in ¹³C high-resolution solid-state NMR spectroscopy.