title: Study on the binding of Thioflavin T to beta-sheet-rich and non-beta-sheet cavities.
abstract: Amyloid fibril formation plays a role in more than 20 diseases including Alzheimer's disease. In vitro detection of these fibrils is often performed using Thioflavin T (ThT), though the ThT binding mode is largely unknown. In the present study, spectral properties of ThT in binding environments representing beta-sheet-rich and non-beta-sheet cavities were examined. Acetylcholinesterase and gamma-cyclodextrin induced a characteristic ThT fluorescence similar to that with amyloid fibrils, whereas beta-cyclodextrin and the beta-sheet-rich transthyretin did not. The cavities of acetylcholinesterase and gamma-cyclodextrin were of similar diameter and only these cavities could accommodate two ThT ions according to molecular modelling. Binding stoichiometry studies also showed a possible binding of two ThT ions. Thus, the characteristic ThT fluorescence is induced in cavities with a diameter of 8-9A and a length able to accommodate the entire length of the ThT ion. The importance of a cavity diameter capable of binding two ThT ions, among others, indicates that an excimer formation is a plausible mechanism for the characteristic fluorescence. We propose a similar ThT binding mode in amyloid fibrils, where cavities of an appropriate size running parallel to the fibril axis have previously been proposed in several amyloid fibril models.
authors.affiliation: Department of Pharmaceutics and Analytical Chemistry, The Danish University of Pharmaceutical Sciences, Universitetsparken 2, 2100 Copenhagen, Denmark. mgm@dfuni.dk
authors.forename: Minna
authors.initials: M
authors.lastname: Groenning
authors.forename: Lars
authors.initials: L
authors.lastname: Olsen
authors.forename: Marco
authors.initials: M
authors.lastname: van de Weert
authors.forename: James M
authors.initials: JM
authors.lastname: Flink
authors.forename: Sven
authors.initials: S
authors.lastname: Frokjaer
authors.forename: Flemming S
authors.initials: FS
authors.lastname: Jørgensen
mesh_terms: D000110:Acetylcholinesterase / Q000737:chemistry; D000682:Amyloid / Q000032:analysis / Q000737:chemistry*; D052160:Benzothiazoles; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry*; D006801:Humans; D008024:Ligands; D008958:Models, Molecular; D011228:Prealbumin / Q000737:chemistry; D017433:Protein Structure, Secondary; D013844:Thiazoles / Q000737:chemistry*; D047408:gamma-Cyclodextrins / Q000737:chemistry
chemical_list: D000682:Amyloid; D052160:Benzothiazoles; D005456:Fluorescent Dyes; D008024:Ligands; D011228:Prealbumin; D013844:Thiazoles; D047408:gamma-Cyclodextrins; C009462:thioflavin T; D000110:Acetylcholinesterase; C023792:gamma-cyclodextrin