A spin-state-selective experiment for measuring heteronuclear one-bond and homonuclear two-bond couplings from an HSQC-type spectrum.

Recently, a set of selective 1D experiments with spin-state-selective excitation for CH spin systems was introduced by Parella and Belloc (J. Magn. Reson., 148, 78-87 (2001)). We have expanded and generalized this concept further, and demonstrated that a very simple experiment utilizing spin-state-selective filtering can be used for simultaneous measurement of heteronuclear 1JNH (or 1JCH) and geminal 2JHH couplings from two-dimensional 15N-1H (or 13C-1H) correlation spectrum. The experiment has very high sensitivity owing to the preservation of equivalent coherence transfer pathways analogous to the sensitivity and gradient enhanced HSQC experiment. However, overall length of the pulse sequence is 1/(2J) shorter than the gradient selected SE-HSQC experiment. Furthermore, the spin-state-selection can be utilized between NH and NH2 (or CH and CH2) moieties by changing the phase of only one pulse. The pulse scheme will be useful for the measurement of scalar and residual dipolar couplings in wide variety of samples, due to its high sensitivity and artifact suppression efficiency. The method is tested on NH2 and CH2 moieties in 15N- and 15N/13C-labeled ubiquitin samples.