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-SelectiveCoherence Transfer (S³CT), via an intermediate state ofheteronuclear IS zero- or double-quantum coherence can transfer the twosingle-quantum coherences on one of the spins exclusively to any one of thetwo single-quantum coherences on the other spin. This fact is used for editinginto two subspectra that are most suitable for extraction of homo- orheteronuclear J coupling constants when S³CT is combined withhomonuclear coherence transfer during a mixing period. Experimentalconfirmation is obtained using a ¹⁵N-labeled 58-residue protein,the C-terminal Kunitz domain from human type VI collagen. The J coupling con-stants determined include ³J_HN-H and³J_N-H related to the and¹ angles, respectively.