FIGURE 5.

Schematics of the two models used to simulate Ca²⁺ and Mg²⁺ uncaging (double arrows) from DMn with the corresponding equilibria. (a) Model (a), in which DMn, CaDMn, and MgDMn all break up into similar photoproducts (PPs). (b) Model (b), in which CaDMn uncages into PP1, whereas DMn and MgDMn uncage into PP2 with a different Ca²⁺ affinity. (c) The difference in the absorption spectra for the PPs of DMn indicates that DMn forms different PPs depending on the ion it binds. The different numbers (1–4) indicate the following absorption spectra: 1, 25 μM DMn; 2, the PPs of 25 μM DMn; 3, the PPs of 25 μM CaDMn; and 4, the PPs of 25 μM MgDMn, all in high EDTA (>5 mM).