title: Thioflavin T: Electronic Circular Dichroism and Circularly Polarized Luminescence Induced by Amyloid Fibrils.
abstract: The circularly polarized luminescence (CPL) spectrum of thioflavin T (ThT) bound to insulin amyloid fibrils has been measured for the first time. It has been found that the samples exhibiting induced circular dichroism (CD) retain the optical activity in the CPL spectra, with the same sign of the rotatory strength. The fluorescence dissymmetry factor is substantial (of the order of magnitude 10(-2) ). Unlike in the corresponding CD and absorption spectra, there is no shift of the CPL band with respect to the fluorescence band. It has been verified that the measured CPL spectra are free from artifacts from circularly polarized scattering of emitted light by conducting additional measurements in a medium with a refractive index similar to insulin (methylsalicylate). The CD and CPL spectra have been interpreted by means of density functional calculations carried out for ThT in its ground and first excited states in different dielectric environments and for ThT interacting with an aromatic ring. It has been found that the presence of an aromatic ring close to the ThT molecule induces Cotton effects of the same order of magnitude as the stabilization of one enantiomeric conformer. Thus, it is expected that both mechanisms contribute to the induced CD and CPL effect to a similar degree.
authors.affiliation: Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093, Warszawa, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Rybicka
authors.affiliation: Università degli Studi di Brescia, Department of Molecular and Translational Medicine, Viale Europa, 11-25123, Brescia, Italy.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Longhi
authors.affiliation: Università degli Studi di Brescia, Department of Molecular and Translational Medicine, Viale Europa, 11-25123, Brescia, Italy.
authors.forename: Ettore
authors.initials: E
authors.lastname: Castiglioni
authors.affiliation: Università degli Studi di Brescia, Department of Molecular and Translational Medicine, Viale Europa, 11-25123, Brescia, Italy.
authors.forename: Sergio
authors.initials: S
authors.lastname: Abbate
authors.affiliation: Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093, Warszawa, Poland.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Dzwolak
authors.affiliation: Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093, Warszawa, Poland.
authors.forename: Viktoria
authors.initials: V
authors.lastname: Babenko
authors.affiliation: Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093, Warszawa, Poland. mpecul@chem.uw.edu.pl.
authors.forename: Magdalena
authors.identifier: http://orcid.org/0000-0002-4872-9031
authors.initials: M
authors.lastname: Pecul
mesh_terms: D000682:Amyloid / Q000737:chemistry*; D052160:Benzothiazoles; D002942:Circular Dichroism; D008163:Luminescent Measurements; D011789:Quantum Theory; D013844:Thiazoles / Q000737:chemistry*
chemical_list: D000682:Amyloid; D052160:Benzothiazoles; D013844:Thiazoles; C009462:thioflavin T
keywords: amyloid fibrils; circular dichroism; circularly polarized luminescence; thioflavin T; time-dependent density functional calculations