Inhibition of the urea-urease reaction by the components of the zeolite imidazole frameworks-8 and the formation of urease-zinc-imidazole hybrid compound

In the past decade, much effort has been devoted to using chemical clock-type reactions in material design and driving the self-assembly of various building blocks. Urea-urease enzymatic reaction has chemical pH clock behavior in an unbuffered medium, in which the induction time and the final pH can be programmed by the concentrations of the reagents. The urea-urease reaction can offer a new alternative in material synthesis, where the pH and its course in time are crucial factors in the synthesis. However, before using it in any synthesis method, it is important to investigate the possible effects of the reagents on the enzymatic reaction. Here we investigate the effect of the reagents of the zeolite imidazole framework-8 (zinc ions and 2-methylimidazole) on the urea-urease reaction. We have chosen the zeolite imidazole framework-8 because its formation serves as a model reaction for the formation of other metal-organic frameworks. We found that, besides the inhibition effect of the zinc ions which is well-known in the literature, 2-methylimidazole inhibits the enzymatic reaction as well. In addition to the observed inhibition effect, we report the formation of a hybrid urease-zinc-2-methylimidazole hybrid material. To support the inhibition effect, we developed a kinetic model which reproduced qualitatively the experimentally observed kinetic curves.

Automated summary

In the past decade, much effort has been devoted to using chemical clock-type reactions in material design and driving self-assembly. The urea-urease enzymatic reaction has shown promising potential in material synthesis, where pH and its temporal evolution play crucial roles. In this study, we investigate the effects of zinc ions and 2-methylimidazole, reagents commonly used in zeolite imidazole framework-8 synthesis, on the urea-urease reaction. We found that both zinc ions and 2-methylimidazole inhibit the enzymatic reaction and report the formation of a hybrid urease-zinc-2-methylimidazole material. A kinetic model is developed to support the observed inhibition effect.