Figure 3.

Schematic of QD-BRET sensor to detect protease activity. QD and luciferase protein are closely linked together through a peptide substrate. In contrast to a quiescent state in the absence of protease (A), an active state (B) of this probe shows that protease cleavage removes the donor protein from QD and disrupts BRET, leading to a loss of bioluminescence-induced QD emission (red line).