Figure 14.

Two Cd²⁺ ions rescue the reaction of S_3’S,P-S with G_2′NH2. In the plot at left, the closed symbols denote two independent determinations of the Cd²⁺ dependence of the reaction of S_3’S,P-S with G_2′NH2, relative to that of the all-oxygen substrate with guanosine. The open symbols denote two independent determinations of k^rel for the reaction of S_3’S,P-S with guanosine, compared to that of the all-oxygen substrate with guanosine. The solid lines are fits of the data to a model in which two Cd²⁺ ions rescue the reaction, while the dashed lines are fits in which three Cd²⁺ ions rescue the reaction. [Data taken from (124).]