Figure 5.

As³⁺ displacement from ZRANB2 apo-peptides by Zn²⁺ is transient. A, Zn²⁺ binding to ZRANB2 apo-peptides is not affected by storage at −20°C for 24 h (colorimetric quantification of free Zn²⁺). B, Zn²⁺ can displace As³⁺ from As³⁺-bound ZRANB2 apo-peptides when readings are taken immediately following incubation (ZNF1 is represented by open circles, ZNF2 by open squares). Please note that these two graphs (ZNF1-Immediate and ZNF2-Immediate) represent the same dataset as in Figure 2C; added for clarity). However, most of that peptide-bound Zn²⁺ is lost if the same samples are stored for 24 h (legend: overnight) at −20°C before the readings are taken (ZNF1 is represented by closed circles, ZNF2 by closed squares; colorimetric quantification of free Zn²⁺). C, UV-Vis spectrophotometric evidence that As³⁺ displaces Zn²⁺ from the ZNF1 apo-peptide if the samples are stored for 24 h (legend: overnight) at −20°C before the reading is taken (legend: overnight), but not if the readings are taken immediately following incubation (legend: immediate). When the readings are taken immediately, addition of Zn²⁺ to the As³⁺-bound apo-peptide causes a significant decrease in absorbance at 285 nm (absorption maximum for ZNF1). However, if the readings are taken after the same samples have been stored for 24 h at −20°C, there is no difference in absorbance of the As³⁺ bound peptides with and without Zn²⁺ addition. ***p<0.001 by Tukey’s multiple comparisons post-hoc test following one-way ANOVA. D, UV-Vis spectrophotometric evidence that As³⁺ displaces Zn²⁺ from the ZNF2 apo-peptide if the samples are stored for 24 h (legend: overnight) at −20°C before reading is taken (legend: overnight), but not if the readings are taken immediately following incubation (legend: immediate). When the readings are taken immediately, addition of Zn²⁺ to the As³⁺-bound apo-peptide causes a significant decrease in absorbance at 285 nm (absorption maximum for ZNF2). However, if the readings are taken after the same samples have been stored for 24 h at −20°C, there is no difference in absorbance of the As³⁺ bound peptides with and without Zn²⁺ addition. ***p<0.001 by Tukey’s multiple comparisons post-hoc test following one-way ANOVA.