Towards selective recoupling and mutual decoupling of dipolar-coupled spinpairs in double-quantum magic-angle spinning NMR experiments on multiply labelled solid-state samples

In solid-slate magic-angle spinning NMR experiments, the combination of sel ective inversion and dipolar recoupling schemes, such as DANTE and C7, allo ws double-quantum coherences to be selectively generated between distinct t ypes of spins, as is experimentally demonstrated here. In such selective in version and multiple quantum excitation experiments, the double quantum coh erences are excited between spins with identical polarisation, but not betw een spins with opposite polarisation. By investigating the decay of longitu dinal magnetisation or the build-up of double-quantum coherences, the respe ctive dipolar pair couplings can be individually measured in the presence o f perturbing couplings, which may even significantly exceed the coupling of interest. (C) 2001 Elsevier Science B.V. All rights reserved.