In vivo bioorthogonal deprotection chemistry has proven a powerful tool to control and synchronise the timing of biological processes. Ultrafast kinetics of reactions such as the inverse electron-demand Diels-Alder pyridazine elimination provide tantalizing opportunities to chemically control processes in living systems.
We are interested in the interaction between host and pathogens, particularly the degradation of bacterial pathogens by phagocytes of the immune system. In our efforts to study the speed of killing of the bacteria, we have begun to develop methodology to control the point in time at which protein expression occurs in the bacteria inside a phagocyte. We therefore chose to make operon regulators for the lac operon of Escherichia coli. We here report the characterization of a new bioorthogonally protected inducer of the lac operon system, by virtue of its modification with trans-cyclooctene as a caging moeity. Inverse electron-demand Diels-Alder (IEDDA) pyridazine elimination liberated the carbohydrate inducer, thereby inducing the gene expression system in a wide variety of biological circumstances.