Sensitivity-enhanced IPAP experiments for measuring one-bond 13C′-13Cα and 13Cα-1Hα residual dipolar couplings in proteins

Sensitivity-enhanced 2D IPAP experiments using the accordion principle for measuring one-bond C-13'-Co-13(alpha) and H-1(alpha) - C-13(alpha) dipolar couplings in proteins are presented. The resolution of the resulting spectra is identical to that of the decoupled HSQC spectra and the sensitivity of the corresponding 1D acquisitions are only slightly lower than those obtained with 3D HNCO and 3D HN(COCA)HA pulse sequences due to an additional delay 2Delta. For cases of limited resolution in the 2D H-15-N-1(N) HSQC spectrum the current pulse sequences can easily be modified into 3D versions by introducing a poorly digitized third dimension, if so desired. The experiments described here are a valuable addition to the suites available for determination of residual dipolar couplings in biological systems. (C) 2004 Elsevier Inc. All rights reserved.