Determination of Internucleotide ^h J _HN Couplings by the Modified 2D J _NN -Correlated [ ¹⁵ N, ¹ H] TROSY

Recent developments in the direct observation of J couplings across hydrogen bonds in proteins and nucleic acids provide additional information for structure and function studies of these molecules by NMR spectroscopy. A J _NN -correlated [ ¹⁵ N, ¹ H] TROSY experiment proposed by Pervushin et al. (Proc. Natl. Acad. Sci. USA 95, 14147-14151, 1998) can be applied to measure ^h J _HN in smaller nucleic acids in an E.COSY manner. However, it cannot be effectively applied to large nucleic acids, such as tRNA ^Trp , since one of the peaks corresponding to a fast relaxing component will be too weak to be observed in the spectra of large molecules. In this Communication, we proposed a modified J _NN -correlated [ ¹⁵ N, ¹ H] TROSY experiment which enables direct measurement of ^h J _HN in large nucleic acids.