Figure 2.

Fluorescence studies to probe the link between metal binding and DNase activity. (a) Cas5d tryptophan fluorescence undergoes quenching with increasing Mg²⁺ concentration (0–500 mM). The concentration of Mg²⁺ for the corresponding curve is indicated in the inset. The fluorescence intensity is shown in arbitrary units (a. u.). (b) Scatchard plot shows a concave-up curve. Here, r is represented as the ratio of ΔF and ΔF_max, where ΔF_max is the differential intensity at the infinite concentration of Mg²⁺. (c) Hill plot in the absence of DNA is shown. The linear trend suggests the existence of cooperativity. (d) The dependence of DNA cleavage on Mg²⁺ was analyzed by Hills plot. The maximal activity is taken as 100%. The percentage activity in the absence of Mg²⁺ is b, and x is the percentage activity in the presence of varying concentrations of Mg²⁺. For (c) and (d), R² represents the square of the goodness of fit, (n_H) denotes the Hill coefficient and K_d indicates the apparent dissociation constant.