Figure 7.

Cell-based FRET assays for characterization of inhibitory effects of K. gracilis leaf extract on virus 2A protease enzymatic activity. HeLa-G2AwtR cells were infected with EV71 or CVA16 at a MOI of 1, and the cells were washed with MEM and then treated with K. gracilis leaf extract at the dosages of 1, 10, 50, 100, and 150 μg/mL. 12, 24, 36, and 48 h after infection, cells were harvested and subjected to measurement by a fluorescent-plate reader with the excitation wavelength at 390/20 nm and emission wavelength at 510/10 nm (for GFP²) or 590/14 nm (for DsRed2). FRET ratio was defined as intensity of emission at 590/14 nm divided by that at 510/10 nm. *P value < 0.05; **P value < 0.01; ***P value < 0.001 by Scheffe test.