Sensitivity-enhanced Experiments for the Measurement of J and Dipolar Coupling Constants

A sensitivity-enhanced IPAP NMR experiment was described in this paper, which separates the ¹H-¹⁵N doublets into two different spectra to alleviate the problem of resonance overlaps and achieve the accurate measurement of J and residual dipolar coupling constants in proteins. This experiment offered 20%–60% sensitivity enhancement over the original IPAP experiment, and therefore produced more measurable resonances. Pulsed field gradient was used for coherence selection. Water-flip-back approach was used for water suppression. The sensitivity-enhanced IPAP experiment was employed in the measurement of ¹J_NH and ¹D_NH constants of the protein UBC9.