The J-multiplied HSQC experiment (MJ-HSQC: S. Heikkinen et al., J. Magn. Reson 137, 243 (1999)) amplifies J coupling constants m times and allows direct observation of the 3 J HNHα coupling constants of peptides and proteins (< 10 kDa). The drawbacks to this method are line broadening in the f 1 -dimension and lower sensitivity. In the J-multiplied HMQC (MJ-HMQC) experiment described here, the PEP-HSQC pulse sequence is replaced by a sensitivity-enhanced HMQC section, and the total decay time for the J-coupling and the chemical shift evolution is shortened by a period of t 1 . This experiment affords narrower linewidth and enhances the sensitivity by 34%, on an average of 105 well-isolated peaks, when compared with the MJ-HSQC experiment.
Bibliographical noteFunding Information:
This work is supported by Grants HKUST6038/98M and HKUST6199/99M from the Research Grant Council of Hong Kong. We thank Dr. K. H. Sze and Dr. David Smith for critical discussions. The Hong Kong Biotechnology Research institute is acknowledged for the purchase of the 500 MHz NMR spectrometer.
- J coupling constant
- N-labeled protein