(A) UV CD spectrum (180–260 nm) of PrP(58–91) (0.032 mM, pH 7.5, no buffer) with the addition of Cu(II) in increments of 0.33 mole-equivalents of CuSO4 from 0 (light blue) up to 7 mole-equivalents (orange). (B) Visible CD spectrum (300–750 nm) of PrP(58–91) (0.033 mM, pH 7.5, no buffer) with the addition of Cu(II) in increments of 1.0 mole-equivalent of CuSO4 from 0 (light blue) up to 6 mole-equivalents (orange). The curves for 1, 3, and 7 mole-equivalents are represented as single points at 570 nm.