Figure 6
Logarithmic plot of the protection factors, PF = kint/kex, calculated from the apparent backbone amide proton/deuteron (H/D) exchange rates, kex, as measured in a series of [1H-15N] HSQC experiments at 20.0 °C (Supplementary Figs S9 and S10). Amide protons with protection factors below about 1 × 102 exchange in less than half an hour and hence too rapidly to be observed with sufficient resonance intensity for quantification. By contrast, amide protons involved in hydrogen bonding in the regular secondary structure elements, which are indicated above the graph, are highly protected from solvent exchange (PF ≈ 5 × 102 to 3 × 104). The backbone amide proton of Ile73 exchanges so slowly (Supplementary Fig. S9) that only an upper bound for kex and hence a lower bound for PF (indicated by the arrow) could be determined.
