Figure 6. Binding of Ni²⁺ to recombinant Hpn as determined by CD.

CD data were obtained for 5 μM Hpn in Tris/HCl buffer, pH 7.4, in both the absence and the presence of 1–5 molar equivalents of Ni²⁺ (as NiSO₄). The arrow indicates the increases in ellipticity values (approx. 217 nm) as the protein was titrated with 0–5 molar equivalents of Ni²⁺.