Fig. 2

Preparation of full-length Tau oligomers. a The oligomerization of hTau40^WT was induced by heparin for 12 h, where the high molecular weight Tau oligomers were separated as soluble fractions by ultracentrifugation. b Glutaraldehyde-fixed Tau oligomers were separated by size-exclusion chromatography (SEC) with lower elution volume as compared to monomeric fractions. c Oligomers containing SEC fractions were confirmed by K9JA western blotting. d The formation of internal cross-β structure and the increased hydrophobicity of hTau40^WT oligomers were confirmed by fluorometric ThS and ANS assay, respectively. e The preformed fibrillar aggregates have shown eightfold and threefold increase in ThS and ANS assay, respectively, as compared to monomers. f CD spectroscopic studies revealed the transition from random coil to the β-sheet structure during the process of hTau40^WT oligomerization and aggregation as compared with monomeric control. g, h hTau40^WT oligomers formed a globular structure with varying size range 5–50 nm as observed by TEM and HR-TEM. i hTau40^WT aggregate formed long fibrillar structures, as seen by uranyl acetate negative staining. j The hTau40^WT oligomers were checked by dot blot staining for the A11 antibody. Significant at the mean difference between treatment groups (X − X`) > Tukey’s criterion (T)