Spin-state-selective coherence transfer via intermediate states of two-spin coherence in IS spin systems: Application to E.COSY-type measurement of J coupling constants

It is demonstrated that a new pulse sequence element, Spin-State-Selective Coherence Transfer ((SCT)-C-3), via an intermediate slate of heteronuclear IS zero-or double-quantum coherence can transfer the two single-quantum coherences on one of the spins exclusively to any one of the two single-quantum coherences on the other spin. This fact is used for editing into two subspectra that are most suitable for extraction of home-or heteronuclear J coupling constants when (SCT)-C-3 is combined with homonuclear coherence transfer-during a mixing period. Experimental confirmation is obtained using a N-15-labeled 58-residue protein, the C-terminal Kunitz domain from human type VI collagen. The J coupling constants determined include (3)J(HN-H alpha) and (3)J(N-H beta) related to the phi and chi(1) angles, respectively.