Fig. 6. Structural ensembles and histograms of the inter-spin distances from the MD simulations of RNA helices labeled at positions (a) 6-16-28 and (b) 6-16-31. Structures and histograms from the first 17 ns are shown in black; those from the last 17 ns are in gray or in color. The N and O atoms of the TEMPO moiety are shown with purple (first 17 ns) and pink (last 17 ns) balls. The reported average distances and their standard deviations (in nm) are calculated from the entire 34 ns simulations.