Tau phosphorylation verified by western blot and SIFT analysis. A. Mass spectroscopy showed that recombinant human tau (isoform 5, 42967 Da) is of high purity. B. While mock phosphorylation (mTau) does not influence SDS-PAGE mobility of recombinant tau, a typical band shift is observed upon tau phosphorylation (pTau). C. SIFT analysis showed labeling of pTau oligomers with the phosphorylated tau specific AT-8 antibody in presence of 1% DMSO indicating antibody binding, while no coaggregation was observed with mTau. Data was normalized against the coaggregation level of mTau with the T46 antibody, which does not require tau phosphorylation. 2D histograms depicting antibody (x-axis) and protein (y-axis) interactions show coaggregates of T46 with both pTau and mTau, while AT-8 only coaggregates with pTau. A scheme describing the appearance of mixed aggregates in 2D histograms is included in Figure 3. Upon combining AT-8 and mTau, only DMSO induced tau aggregates are visible along the y-axis, similar to the control antibody 6E10. Measurements were taken from 12 independent samples; each sample was measured four times. Levels of significance are displayed as * = p < 0.05; ** = p < 0.01; ‡ = p < 0.001.