Thioflavine S (CAS 1326-12-1)

Thioflavine S, known chemically as benzothiazolium, 3,6-dimethyl-2-[2-(4-methylphenyl)ethenyl]-, chloride, and identified by the CAS number 1326-12-1, is a cationic benzothiazole dye that exhibits particular fluorescence properties. This chemical is primarily utilized in scientific research for its ability to bind selectively to amyloid fibrils, which are aggregates of proteins that are typically associated with various amyloid diseases. Thioflavine S fluoresces upon binding to these fibrils, thereby increasing its fluorescence intensity, a property that researchers exploit to visually detect and quantify the presence of amyloid structures in biological specimens. The mechanism through which Thioflavine S binds involves its interaction with the cross-β sheet structure of amyloid fibrils; the dye intercalates into the stacked β-sheet structure, resulting in a shift in its emission spectrum when exposed to light of specific wavelengths. This interaction not only enables the visualization of amyloid deposits in histological sections under a fluorescence microscope but also facilitates the study of amyloidogenesis in vitro. By providing a means to monitor the aggregation of proteins into fibrils, Thioflavine S has become a valuable tool in the fundamental research of protein misfolding diseases, aiding in the understanding of the pathogenesis and progression of these conditions at a molecular level.