1H-1H MQ spectroscopy

SQ NMR spectroscopy is the basis of modern spectral characterization. However, MQ provides access to unique structural details by correlating coupled spins. MQ spectroscopy simplifies spectra and unique correlations provide structural information. MQ spectroscopy has been extensively used to suppress background signal, measure torsional angles, study dynamics and in spectral assignment.  However in case of unlabeled protonated samples MQ coherences have played a unique role.  At fast MAS, MQ spectra suffer from t1 noise arising from various factors. We have been developing DQ-SQ and TQ-SQ 1H-1H correlation experiments that result in higher MQ excitation and filtering efficiency. These sequences are not gamma dependent. In case of 1H TQ, the sensitivity of the gamma-free sequences is a factor of 3-4 higher than previously know TQ recoupling sequences and are largely free from t1 artifacts arising due to rotor fluctuations. 

This is collaboration with Dr Yusuke Nishiyama and Prof. Rongchun Zhang. 

References

• Yusuke Nishiyama, Vipin Agarwal and Rongchun Zhang Efficient Symmetry-Based γ-Encoded DQ Recoupling Sequences for Suppression of t1-Noise in Solid-State NMR Spectroscopy at Fast MAS Solid State Nucl. Magn. Reson., 114, 101734 (2021)
• Yusuke Nishiyama, Vipin Agarwal  and Rongchun Zhang t₁-noise suppression by γ-free recoupling sequences in solid-state NMR for structural characterization of fully protonated molecules at fast MAS  J. Phys. Chem. C,  124, 48, 26332–26343 (2020)