Thioflavin

Chembox new
Name = Thioflavin T
ImageFile = Thioflavin T.png ImageSize =
ImageFile1 = Thioflavin-T-3D-balls.png ImageSize1 = 200px
IUPACName = 4-(3,6-dimethyl-1,3-benzothiazol-3
-ium-2-yl)-N,N-dimethylaniline chloride
OtherNames =
Section1 = Chembox Identifiers
CASNo = 2390-54-7
PubChem = 16953
SMILES = CC1=CC2=C(C=C1) [N+] (=C(S2)
C3=CC=C(C=C3)N(C)C)C. [Cl-]
Section2 = Chembox Properties
Formula = C₁₇H₁₉ClN₂S
MolarMass = 318.86 g/mol
Appearance =
Density =
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Section3 = Chembox Hazards
MainHazards =
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Thioflavin can refer to either of two dyes used for histology staining.

Thioflavin T (Basic Yellow 1 or CI 49005) is a benzothiazole salt obtained by the methylation of dehydrothiotoluidine with methanol in the presence of hydrochloric acid. The dye is used to visualize plaques composed of amyloid beta found in the brains of Alzheimer's disease patients as well as other amyloid proteins. When it binds to beta sheets, such as those in amyloid oligomers, the dye undergoes a characteristic 115 nm red shift of its excitation spectrum that may be selectively excited at 442 nm, resulting in a fluorescence signal at 482 nm H. LeVine III, "Methods in Enzymology." 309, 274 (1999) ] . This red shift is only observed if amyloid fibrils are present. It will not undergo this red shift upon binding to precursor monomers or small oligomers [H. LeVine III, "Prot. Sci." 2, 404 (1993) ] , or if there is a high beta sheet content [H. LeVine III, "Amyloid Int. J. Exp. Clin. Invest." 2, 1 (1995) ] . If no amyloid fibrils are present in solution, excitation and emission occur at 342 and 430 nm repectively .

Thioflavin S is a homogenous mixture of compounds that results from the methylation of dehydrothiotoluidine with sulfonic acid. It is also used to stain Alzheimer's plaques. Like Thioflavin T it binds to amyloid fibrils but not monomers and gives a distinct spectral shift upon binding . However the dye is unable to be used in quantitative measurements of fibril solutions due to its high background fluorescence.

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