title: Thioflavine-T and Congo Red reveal the polymorphism of insulin amyloid fibrils when probed by polarization-resolved fluorescence microscopy.
abstract: Amyloid fibrils are protein misfolding structures that involve a β-sheet structure and are associated with the pathologies of various neurodegenerative diseases. Here we show that Thioflavine-T and Congo Red, two major dyes used to image fibrils by fluorescence assays, can provide deep structural information when probed by means of polarization-resolved fluorescence microscopy. Unlike fluorescence anisotropy or fluorescence detected linear dichroism imaging, this technique allows to retrieve simultaneously both mean orientation and orientation dispersion of the dye, used here as a reporter of the fibril structure. We have observed that insulin amyloid fibrils exhibit a homogeneous behavior over the fibrils' length, confirming their structural uniformity. In addition, these results reveal the existence of various structures among the observed fibrils' population, in spite of a similar aspect when imaged with conventional fluorescence microscopy. This optical nondestructive technique opens perspectives for in vivo structural analyses or high throughput screening.
authors.affiliation: Aix Marseille Université, CNRS, Ecole Centrale Marseille, Institut Fresnel, 13013 Marseille, France. julien.duboisset@Fresnel.fr
authors.forename: Julien
authors.initials: J
authors.lastname: Duboisset
authors.forename: Patrick
authors.initials: P
authors.lastname: Ferrand
authors.forename: Wei
authors.initials: W
authors.lastname: He
authors.forename: Xiao
authors.initials: X
authors.lastname: Wang
authors.forename: Hervé
authors.initials: H
authors.lastname: Rigneault
authors.forename: Sophie
authors.initials: S
authors.lastname: Brasselet
mesh_terms: D000682:Amyloid / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D052160:Benzothiazoles; D002417:Cattle; D002942:Circular Dichroism; D003224:Congo Red / Q000737:chemistry*; D005454:Fluorescence Polarization; D007328:Insulin / Q000737:chemistry* / Q000378:metabolism; D008856:Microscopy, Fluorescence; D017433:Protein Structure, Secondary; D013844:Thiazoles / Q000737:chemistry*
chemical_list: D000682:Amyloid; D052160:Benzothiazoles; D007328:Insulin; D013844:Thiazoles; C009462:thioflavin T; D003224:Congo Red