CARBON ASSIGNMENTS AND HETERONUCLEAR COUPLING-CONSTANTS FOR AN RNA OLIGONUCLEOTIDE FROM NATURAL ABUNDANCE C-13-H-1 CORRELATED EXPERIMENTS

Complete assignments of the proton-linked carbons for the oligoribonucleotide 5'(GGACUUCGGUCC) have been obtained from 2D C-13-H-1 correlated experiments at natural abundance. High-quality spectra have been collected at RNA concentrations commonly used in proton experiments (2 mM). Heteronuclear one-bond scalar couplings have been measured from high-resolution spectra. The results demonstrate the editing power of the C-13-H-1 correlation in the very crowded sugar region of the proton NMR spectrum of RNA. Thus, 2D C-13-H-1 correlated experiments can be one of the main tools used for RNA proton spectral assignments. Both the carbon chemical shifts and the C-13-H-1 couplings are shown to be sensitive to the conformation of the sugar and the phosphodiester backbone, previously characterized for this oligoribonucleotide using proton and phosphorus NMR data. The potential of C-13 NMR in the structural analysis of RNA is evident from the data reported here.