Fig. 3.

Secondary chemical shifts, Δδ, probe residual structure in the C-terminal region of HSP27. Secondary chemical shifts are defined as the difference between the experimentally measured chemical shift of a given nuclei in a given residue and the same nuclei from the same residue in a random coil conformation, typically extracted from a database of known values. Shown here are the secondary chemical shifts for ¹³Cα (a), ¹³Cβ (b), ¹³CO (c), and ¹H^N (d) nuclei in HSP27. The arrow depicts the position of P194 in the amino acid sequence. Note that artificially large values are observed for G193 due to its i-1 position to P194. e The ¹³C chemical shifts from the CTR of HSP27 were used as input to calculate the secondary structure propensity (SSP) of this region. The y-axis depicts the propensity to populate α-helical (+1.0) or β-strand (−1.0) conformations, with a value of, e.g., −0.2 corresponding to 20% β-strand. The cis-P194 state is shown in red and the trans-P194 state in black