Figure 6.

Values of Δδ for ¹³C^α spins in HP67. (a) ¹³C^α secondary shifts, Ω_sec, are plotted versus residue number. A schematic of the protein secondary structure colored to reflect the subdomains defined in Fig. 1 is provided for reference. In (b) the absolute value of the chemical shift difference, |Δδ|, between the intermediate and native state ¹³C^α resonances are plotted versus residue number as solid bars colored to match the color coding in Fig. 5. Values of Δ δ were calculated from φ_ex assuming a population p₂ = (1.11 ± 0.09)% for the intermediate. White bars represent values of Δδ that are likely to be negative based on the corresponding sign of Ω_sec. For residues in the N-terminal domain, Δδ is large due to the change in chemical environment associated with the unfolding transition. Residues in the C-terminal domain show very little change in chemical shift with the exception of Leu75 and Phe76.