Fig. 4

Ca²⁺ and Cu²⁺ induce increases in α-helical secondary structure measured by far UV circular dichroism. Curves show mean molar ellipticity vs. wavelength for each experimental condition: Apo (gray), bound to Cu²⁺ (orange), bound to Ca²⁺ (blue), and bound to both Cu²⁺ and Ca²⁺ (red)