Fig. 3.

Expanded region of the 2D ¹H,¹H TOCSY experiment (Table 1, XIV.) correlating pyrimidine H5–H6 proton chemical shifts via their ³J coupling. Linewidths are approximately inversely proportional to the base order parameter, resulting in sharp signals for flexible residues that exhibit a lower than the global τ_c. 1D traces for selected residues are shown in the 2D. The flexible loop residues U18, C19, and C20 and the non-native 3'-terminal c34 are highlighted in red; helical residues U9 and U11 are shown in black