Figure 3: Inhibition of PLG binding to L. interrogans by ACA. Low-passage virulent L. interrogans serovar Copenhageni cells were treated with the following: PLG together with uPA (PLG + uPA), PLG together with uPA with the addition of crescent concentrations of ACA (0.01 to 1,000 mM ACA), PLG alone (PLG), uPA alone (uPA), ACA alone (ACA), and no additions (PBS). The cleavage of the plasmin-specific substrate D-Val-Leu-Lys 4-nitroanilide dihydrochloridein by the treated spirochetes was measured by absorbance readings at 405 nm. Bars represent mean absorbance ± the standard deviation of three replicates for each experimental group and are representative of three independent experiments. Statistically significant substrate degradation inhibition results in comparison to the positive control (PLG + uPA) are shown: P < 0.01 (*) and P < 0.0001 (**).