Fig. 2.

Principle of $\mathrm{\beta }$-lactamase enzyme-activated fluorophore ($\mathrm{\beta }$-LEAF). Before the introduction of the enzyme (the system is in “off” state), two fluorophores are in close proximity to each other and as a result of static quenching, the system does not produce fluorescence. When the enzyme cleaves the β-lactam ring (the system is in “on” state), the two fluorophores are separated from each other and consequently the system produces fluorescence.