The effect of methylene blue dose and 1.93 J/cm2 laser light on the proteolytic activity of V8 protease. An equal volume of either methylene blue (S+) (concentrations ranging from 1-20 μM) or PBS (S-) was added to V8 protease and samples were either exposed to laser light with an energy density of 1.93 J/cm2 (L+) (black bars) or kept in the dark (L-) (white bars). The activity of the V8 protease was assessed using the azocasein hydrolysis assay. Error bars represent the standard deviation from the mean. *** P < 0.001 (ANOVA). Experiments were performed three times in triplicate and the combined data are shown.