[C-13,C-13]- and [C-13,H-1]-TROSY in a triple resonance experiment for ribose-base and intrabase correlations in nucleic acids

A novel TROSY (transverse relaxation-optimized spectroscopy) element is int roduced that exploits. cross-correlation effects between C-13-C-13 dipole-d ipole (DD) coupling and C-13 chemical shift anisotropy-(CSA) of aromatic ri ng carbons. Although these C-13-C-13 effects are smaller than the previousl y described [C-13,H-1]-TROSY effects for aromatic C-13-H-1 moieties, their constructive use resulted in further transverse relaxation-optimization by up to 15% for the resonances in a 17 kDa protein-DNA complex. As a practica l application, two- and three-dimensional versions of the HCN triple resona nce experiment for obtaining ribose-base and intrabase correlations in the nucleotides of DNA and RNA (Sklenar, V.; Peterson, R. D.; Rejante, M. R.; F eigon, J. J. Biomol. NMR 1993, 3, 721-727) have been implemented with [C-13 ,H-1]- and [C-13,C-13]- TROSY elements to reduce the rate of transverse rel axation during the polarization transfers between ribose (13)C1' and base ( 15)N1/9 Spins, and between (13)C6/8 and N1/9 within the bases. The resultin g TROSY-HCN experiment is user-friendly, with a straightforward, robust exp erimental setup. Compared to the best previous implementations of the HCN e xperiment, 2-fold and 5-fold sensitivity enhancements have been achieved fo r ribose-base and intrabase connectivities, respectively, for C-13,N-15-lab eled nucleotides in structures with molecular weights of 10 and 17 kDa. TRO SY-HCN experiments should be applicable also with significantly larger mole cular weights. By using modified TROSY-HCN schemes, the origins of the sens itivity gains' have been analyzed.