Fig. 1. (a) Structural model of the 26mer Box C/D RNA (light blue) bound to the L7Ae protein (grey) from Pf, established by alignment of the previously determined MAS NMR structure (PDB ; 2N0R)3 of the RNA from Pf with a homologous RNA sequence in a larger complex (PDB ; 3NMU). (b) Ribose and base C5–H5 regions of ¹³C–¹H CP-HSQC spectra recorded on a 800 MHz spectrometer at MAS rates of 20, 40, 60 and 109 kHz, characteristic for commercial 3.2, 1.9, 1.3 and 0.7 mm MAS probes. 1D traces of a representative resonance with the corresponding proton line width are shown in the bottom right corner. (c) Bulk coherence lifetimes (T₂′) of base H6, H8 and H2 (brown squares), ribose H1′ (cyan circles) and other ribose H2′–H5′′ protons (blue triangles) measured on a 800 MHz spectrometer and MAS frequencies from 20 to 109 kHz.