FIGURE 4.

Imino proton regions of 1D jump–return echo spectra acquired at 10°C, pH 6.0 for SL1-Δ16/19/20/35 (A), SL2 (B), and SL1-Δ16/19/20/35-SL2 (C) RNA. See Fig. 3B for sequences for these RNA constructs. Note that the spectra for SL2 are characterized by slow conformational heterogeneity at the base of SL2 (G42-C56 and A43-U55 base pairs). The imino protons corresponding to U48 and U49 in the SL2 pentaloop are also indicated. The assignment of U12 is based on a weak NOE to a C32 amino proton.