Figure 4.

Correlations between δP and ΔRDCs or internucleotide distances. The relative orientation of bases of the same strand in a base step is characterized either by ΔRDCs (left panels) or by internucleotide distances (right panels). The backbone conformation is represented by ³¹P chemical shifts (δP). ΔRDCs were calculated from RDCs measured at 25°C; δP and D_inter were collected at 20°C. The data exclude the terminal steps, which are shown in Figure 7. Left: Correlations between δPs and ΔRDC_C6/8-H6/8, ΔRDC_C3′-H3′ and ΔRDC_C4′-H4′., with ΔRDC = RDC_{residue i+1} – RDC_{residue i}. Right: Correlations between δPs and the internucleotide distances D_inter(H6/8_i-H6/8_i+1), D_inter(H2′_i-H6/8_i+1) and D_inter(H2″_i-H6/8_i+1). This data set also contains measurements previously collected on the Jun-Fos oligomer (37,68). Note that D_inter(H6/8_i-H6/8_i+1) > 5 Å are extracted from NOESY spectra recorded with a mixing time of 300 ms and are thus less precisely measured than shorter distances. The points in blue in panels involving ΔRDC_C3′-H3′, ΔRDC_C4′-H4′, D_inter(H2′_i-H6/8_i+1) and D_inter(H2″_i-H6/8_i+1) correspond to dinucleotides with detectable populations of East or North sugars. The vertical bars are the estimated experimental errors on ΔRDC and D_inter (see Materials and Methods). The experimental error on δPs (horizontal bars) is estimated to ±0.05 ppm for the left panel plots and to ±0.02 ppm for the right panel plots (see Materials and Methods). The best linear fits are represented with red lines; the residual standard deviations are depicted by dashed red lines. The characteristics of the correlations are reported in Table 2.