Interference of low-molecular substances with the thioflavin-T fluorescence assay of amyloid fibrils
Article first published online: 14 NOV 2011
Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.
Journal of Peptide Science
Volume 18, Issue 1, pages 59–64, January 2012
How to Cite
Noormägi, A., Primar, K., Tõugu, V. and Palumaa, P. (2012), Interference of low-molecular substances with the thioflavin-T fluorescence assay of amyloid fibrils. J. Peptide Sci., 18: 59–64. doi: 10.1002/psc.1416
- Issue published online: 26 DEC 2011
- Article first published online: 14 NOV 2011
- Manuscript Accepted: 18 AUG 2011
- Manuscript Revised: 11 AUG 2011
- Manuscript Received: 9 JUN 2011
Abnormal fibrillization of amyloidogenic peptides/proteins has been linked to various neurodegenerative diseases such as Alzheimer's and Parkinson's disease as well as with type-II diabetes mellitus. The kinetics of protein fibrillization is commonly studied by using a fluorescent dye Thioflavin T (ThT) that binds to protein fibrils and exerts increased fluorescence intensity in bound state. Recently, it has been demonstrated that several low-molecular weight compounds like Basic Blue 41, Basic Blue 12, Azure C, and Tannic acid interfere with the fluorescence of ThT bound to Alzheimers' amyloid-β fibrils and cause false positive results during the screening of fibrillization inhibitors. In the current study, we demonstrated that the same selected substances also decrease the fluorescence signal of ThT bound to insulin fibrils already at submicromolar or micromolar concentrations. Kinetic experiments show that unlike to true inhibitors, these compounds did neither decrease the fibrillization rate nor increase the lag-period. Absence of soluble insulin in the end of the experiment confirmed that these compounds do not disaggregate the insulin fibrils and, thus, are not fibrillization inhibitors at concentrations studied. Our results show that interference with ThT test is a general phenomenon and more attention has to be paid to interpretation of kinetic results of protein fibrillization obtained by using fluorescent dyes. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.