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Mechanism of thioflavin T binding to amyloid fibrils

Academic Article
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Overview

authors

  • Khurana, R.
  • Coleman, C.
  • Ionescu-Zanetti, C.
  • Carter, S. A.
  • Krishna, V.
  • Grover, Rajesh
  • Roy, R.
  • Singh, S.

publication date

  • 2005

journal

  • Journal of Structural Biology  Journal

abstract

  • Thioflavin T is a benzothiazole dye that exhibits enhanced fluorescence upon binding to amyloid fibrils and is commonly used to diagnose amyloid fibrils, both ex vivo and in vitro. In aqueous solutions, thioflavin T was found to exist as micelles at concentrations commonly used to monitor fibrils by fluorescence assay ( approximately 10-20 microM). Specific conductivity changes were measured at varying concentration of thioflavin T and the critical micellar concentration was calculated to be 4.0+/-0.5 microM. Interestingly, changes in the fluorescence excitation and emission of thioflavin T were also dependent on the micelle formation. The thioflavin T micelles of 3 nm diameter were directly visualized using atomic force microscopy, and bound thioflavin T micelles were observed along the fibril length for representative fibrils. Increasing concentration of thioflavin T above the critical micellar concentration shows increased numbers of micelles bound along the length of the amyloid fibrils. Thioflavin T micelles were disrupted at low pH as observed by atomic force microscopy and fluorescence enhancement upon binding of thioflavin T to amyloid fibrils also reduced by several-fold upon decreasing the pH to below 3. This suggests that positive charge on the thioflavin T molecule has a role in its micelle formation that then bind the amyloid fibrils. Our data suggests that the micelles of thioflavin T bind amyloid fibrils leading to enhancement of fluorescence emission.

subject areas

  • Amyloid
  • Binding Sites
  • Deuterium
  • Fluorescence
  • Fluorescence Polarization
  • Fluorescent Dyes
  • Hydrogen-Ion Concentration
  • Micelles
  • Microscopy, Atomic Force
  • Molecular Structure
  • Nuclear Magnetic Resonance, Biomolecular
  • Protein Binding
  • Solutions
  • Spectroscopy, Fourier Transform Infrared
  • Thiazoles
  • Water
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Research

keywords

  • amyloid binding dyes
  • atomic force microscopy
  • critical micellar concentration
  • fluorescence enhancement
  • thioflavin T micelles
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Identity

International Standard Serial Number (ISSN)

  • 1047-8477

Digital Object Identifier (DOI)

  • 10.1016/j.jsb.2005.06.006

PubMed ID

  • 16125973
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Additional Document Info

start page

  • 229

end page

  • 238

volume

  • 151

issue

  • 3

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