CD spectra of N (thick lines, at 20°C, pH 7.0) and D (thin line, at 70°C, pH 7.0) forms of holo-CP (solid lines) and apo-CP (dotted lines). For comparison, GuHCl-perturbed CP (at 20°C, pH 7.0) is also shown (dash-dot line). CD spectra of 3Cu-CP N and D forms are indistinguishable of those of holo-CP.