Kinetic analysis of polymerization using GSK-3β phosphorylated tau. A comparison between control (non-phosphorylated, open symbols) and phosphorylated tau (filled symbols) showed that phosphorylation altered polymerization kinetics, particularly in the first 30 minutes of the reaction. Panel A shows kinetics over the entire 20-h reaction time. Panel B shows only the first 30 minutes (the section boxed by a dotted line in panel A). Two ratios of ARA inducer:tau protein were compared: a suboptimal ratio (labeled 25 μM, representing the concentration of ARA, diamonds) and an optimal ratio (labeled 75 μM, circles). The tau protein concentration was 2 μM for all kinetic reactions. Changes in ThS fluorescence intensity (y axis) was used to indicate the extent of polymerization and measurements were in arbitrary units (a.u.). Error bars are +/- SEM. Every 40th data point was plotted for ease in interpretation.