TEM analysis of mock phosphorylation reactions. Standard polymerization reactions containing 2 μM tau were induced with either a low (25 μM), or optimal (75 μM) concentration of ARA (Panels A and B, respectively). Panels C-F show polymerization reaction products in which mock-phosphorylated tau had been polymerized. In panel C and D, GSK-3β had been omitted from the phosphorylation reaction (- GSK + ATP) and in panel E and F, ATP had been omitted from the phosphorylation reaction (+ GSK – ATP). The 25 μM ARA reactions were diluted five fold, the 75 μM ARA reactions were diluted ten fold prior to grid preparation.