Figure 2.

The three Hsts are all soluble at a physiological ratio of Zn²⁺ to peptide but differ in relative Zn²⁺ affinity. (A) Percent solubility of 15 µM Hst 5 (red), Hst 5ΔMB (blue), and P113 (green) in 10 mM sodium phosphate buffer pH 7.4 with increasing ratio of Zn²⁺ incubated at room temperature for 30 min. Peptide solubility was measured via NanoDrop A205 after removal of insoluble aggregates by centrifugation. (B) Binding competition assay with Zincon and peptides at 20 µM in 10 mM sodium phosphate buffer pH 7.4 to establish relative affinity of Hst 5 (red), Hst 5ΔMB (blue), and P113 (green) for Zn²⁺ at increasing molar ratios. Absorbance of Zincon at 621 nm was measured as an inverse indicator of relative peptide affinity, as Zincon has a blue color when bound to zinc. Experiments were performed in triplicate and averaged.