Fig. 6.

Schematic illustration of the suggested effect of adding Cu (Zn) to the Zn–(Cu)–4R₈-complex. Cu(II) and Zn(II) ions are drawn as magenta and yellow dots, respectively. Only the bonds between metals and His residues imidazole rings are indicated (short blue segments). In the first (second) row we display the metal–peptide arrangements identified in this work (in Stellato et al. 2011). The three columns show the effect of ending with a system with zero, low, and high Cu concentration. In this work Cu was added to a sample already containing Zn, whereas Stellato et al. (2011) prepared samples at different Cu concentrations and then added Zn at a later stage. The number of magenta (Cu) and yellow (Zn) dots per tetra-octarepeat shown in the different panels is indicative only and does not represent the real proportion among tetra-octarepeats, Cu and Zn