Millisecond motions in H48C-4MI. Dispersion curves for V43, C84, and N71 are displayed. On the left are dispersion curves for 1H,15N-H48A pH = 6.4 and 1H,15N-H48C, pH = 7.0. The right panel shows CPMG dispersion curves 2H,15N-WT, pH = 6.4 and 1H,15N-pH = 7.0 and 1H,15N-H48C-4MI pH = 7.0. Labels identifying the appropriate enzyme are placed closest to the relevant dispersion curve. The data are fit with the fast-limit CPMG dispersion equation. The ribbon structure of RNase A shows the location of these residues as single spheres. The side chain of thia-imidazole is shown as a sphere representation.