- Novel Three-Dimensional Correlation Experiments to Reveal Local Proton Networks under Fast Magic-Angle Spinning at Natural 13C Abundance
Novel Three-Dimensional Correlation Experiments to Reveal Local Proton Networks under Fast Magic-Angle Spinning at Natural 13C Abundance
1H double quantum (DQ)/1H single quantum (SQ) correlation solid-state NMR spectroscopy is widely used to obtain internuclear 1H-1H proximities, especially at fast magic angle spinning (MAS) rate > 60 kHz. However, 1H signals are not well-resolved due to intense 1H-1H homonuclear dipolar interactions even at the attainable maximum MAS frequencies of ~100 kHz to date. We have recently introduced novel three-dimensional (3D) experiments to resolve the 1H DQ/1H SQ correlation peaks using the additional 13C dimension. Although the low natural abundance of 13C (1.1%) significantly reduces the sensitivities, the 1H indirect measurements alleviate this issue and make this experiment possible. The two different implementations of 13C/1H DQ/1H SQ correlations and 1H DQ/13C/1H SQ correlations have been discussed and demonstrated using L-histidine.HCl.H2O at natural abundance to reveal the local 1H-1H networks nearby each 13C. In addition, the complete 1H resonance assignments have been achieved from a single 3D 13C/1H DQ/1H SQ experiment. We have also demonstrated the applicability of our proposed method on a biologically relevant molecule capsaicin.
The 2D 1H DQ/1H SQ spectrum of capsaicin (left) is too complex due to signal overlaps. On the other hand, the 13C-filtered spectrum (right) yields well-resolved peaks and thus signal assignment is possible. Both spectra were recorded at 70 kHz MAS. Please refer to the original paper for more detail.
- M. Malon, M. K. Pandey and Y. Nishiyama, J. Phys. Chem. B, 2017, 121, 8123-8131.
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