SEQUENTIAL ASSIGNMENTS IN UNIFORMLY C-13-LABELED AND N-15-LABELED RNA- THE HC(N,P) AND HC(N,P)-CCH-TOCSY EXPERIMENTS

An approach for the simultaneous acquisition of HCN and HCP as well as HCN-CCH-TOCSY and HCP-CCH-TOCSY triple resonance data sets for C-13-/ N-15-labelled RNAs is presented. The new HCN-CCH-TOCSY scheme unambigu ously links all sugar resonances to the base nitrogen. In addition, si multaneous acquisition of HCN-CCH-TOCSY and HCP-CCH-TOCSY data sets pr ovides sequential and base-type information in a single experiment, th ereby saving data acquisition time as well as providing complementary data sets that are useful in clarifying ambiguous assignments. Virtual ly complete sequence-specific phosphate-ribose H-1, P-31, and base (15 )N1,9 assignments as well as partial C-13 assignments could be obtaine d in a single experiment for a 0.5-mM sample of a 19-mer ribonucleotid e.