Thioflavin T is a fluorescent dye that binds to beta sheet-rich structures such as those in alpha synuclein fibrils. Upon binding, the emission spectrum of the dye experiences a red-shift and increased fluorescence intensity. Thioflavin T emission curves show a limited increase in fluorescence (correlated to alpha synuclein aggregation) over time in A53T alpha synuclein monomers (SPR-325). A much greater increase in fluorescence is seen when 100 uM monomer (SPR-325) is combined with 10 nM of fibrils (SPR-326) as the fibrils seed the formation of new fibrils from the pool of active monomers. Thioflavin T ex = 450 nm, em = 485 nm.