A novel TROSY (transverse relaxation-optimized spectroscopy) element is introduced that exploits. cross-correlation effects between C-13-C-13 dipole-dipole (DD) coupling and C-13 chemical shift anisotropy-(CSA) of aromatic ring carbons. Although these C-13-C-13 effects are smaller than the previously 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 practical application, two- and three-dimensional versions of the HCN triple resonance experiment for obtaining ribose-base and intrabase correlations in the nucleotides of DNA and RNA (Sklenar, V.; Peterson, R. D.; Rejante, M. R.; Feigon, 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 relaxation 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 resulting TROSY-HCN experiment is user-friendly, with a straightforward, robust experimental setup. Compared to the best previous implementations of the HCN experiment, 2-fold and 5-fold sensitivity enhancements have been achieved for ribose-base and intrabase connectivities, respectively, for C-13,N-15-labeled nucleotides in structures with molecular weights of 10 and 17 kDa. TROSY-HCN experiments should be applicable also with significantly larger molecular weights. By using modified TROSY-HCN schemes, the origins of the sensitivity gains' have been analyzed.