Conclusions
We have shown that in 1H-{ NOT DQ1 4 } D-HMQC experiments modified composite pulses are more robust with respect to 14N offset than single-pulses and more efficient than WURST pulses. It has recently been shown that 1H-{14NSQ} D-HMQC experiments with selective 14NSQ excitation are very efficient and robust [20]. The present overtone strategy with modified composite pulses is thus an alternative approach for recording high resolution 14N signals. This method can easily be generalized and the shaped-pulses can be tailored to only excite the useful NOT DQ1 4 frequency ranges. Thesecomplementaryindirect-detectionmethods,witheither 14NSQ or NOT DQ1 4 , represent two promising tools to get insights into more complex chemical environments of 14N species in biomolecules.