Thioflavin T is a fluorescent dye that binds to beta sheet-rich structures, such as those in tau fibrils. Upon binding, the emission spectrum of the dye experiences a red-shift and increased fluorescence intensity. Thioflavin T emission curves show increased fluorescence (correlated to tau aggregation) over time in tau monomers (SPR-327). A greater increase in fluorescence is seen when 50 uM monomer (SPR-327) is combined with 10 nM PFFs (SPR-329 or SPR-330), as the fibrils seed the formation of new fibrils from the pool of monomers. Thioflavin T ex = 450 nm, em = 485 nm. 10 uM heparin was added to each well.