Double spin-state-selective coherence transfer. Application for two-dimensional selection of multiplet components with long transverse relaxation times

The spin-state-selective coherence transfer (S 3 CT) pulse sequence element has earlier been introduced as a means of editing the two resonances of a doublet (Sørensen, M. D., et al. 1997, J. Biomol. NMR, 10, 181). This paper demonstrates how two consecutive S 3 CT elements in a mixing sequence can be used to edit the four multiplet components of a two-dimensional correlation cross peak of a two-spin system. A particular phase setting in the mixing sequence yields one component in the echo and one in the anti-echo part. However, since one of them passes through an intermediate state of zero-quantum coherence while the other passes through double-quantum coherence, a phase cycle or pulsed field gradients can separate the two. The resulting (S 3 CT) 2 HSQC pulse sequence corresponds to transverse relaxation optimized spectroscopy (TROSY) (Pervushin, K., et al., 1997, Proc. Nat. Acad. Sci. USA, 94, 12366). Experimental confirmation is provided using a 15 N-labelled protein, neural cell adhesion molecule (NCAM) modules 1 and 2, with a molecular weight of about 20kDa.