Figure 3.

Peptide A assumes α-helical structure upon binding to the small subunit of m-calpain. (A) The CD spectrum of the small subunit of human m-calpain (21K) at 0.4 mg/mL was recorded in the absence (I) and presence (II) of an equimolar concentration of peptide A at 3 mM Ca²⁺ in water. (B) The difference spectrum obtained by subtracting the spectrum of the small subunit from the joint spectrum (III). For a comparison, the spectra of peptide A in TFE (IV) and water (V), taken from Figure 1A ▶ and normalized to the given peptide concentration, are also shown.