Figure 4.

Zn²⁺ binding to His residues at pH 7 promotes further oligomerization.A, ¹H-¹⁵N HSQC before (green) and after (blue) the 2-month pause. Some distinct residues are labeled. B, ¹H-¹⁵N before (blue) and after (black) the addition of ZnCl₂. His and Gln signals (labeled) weaken sharply after addition of Zn²⁺. C, the largest drop in peak intensity upon Zn addition occurs for residues of the Q/H-rich segments (rose band). D, conformational chemical shifts for ¹³Cα (black), ¹³Cβ (red), and ¹³CO (blue) strongly suggest that the molecules remaining in solution lack helical zones and are disordered.