Related Experiment Video
Updated: Apr 16, 2026

In Vitro Aggregation Assays Using Hyperphosphorylated Tau Protein
Published on: January 2, 2015
Effect of acidic and basic pH on Thioflavin T absorbance and fluorescence
Ellen V Hackl1, Joseph Darkwah, Geoff Smith
1Leicester School of Pharmacy, Faculty of Health and Life Sciences, De Montfort University, Leicester, UK.
Abstract:
Thioflavin T (ThT) is a fluorescent dye able to enhance significantly its fluorescence quantum yield upon binding to protein amyloids. ThT assay is widely used to detect and quantify amyloids in a variety of conditions, including solutions with different pH levels. In the present work, the effect of acidic and basic pH on the conformation of the ThT molecule and its absorption and fluorescence properties was studied. The results show that both acidic and basic pH decrease significantly the intensity of ThT absorption in the visible region and fluorescence emission intensity. Low pHs induce an immediate "all-or-nothing" decrease in the ThT signal, while in alkaline solutions the ThT signal decreases gradually over time. pH-induced signal quenching is less in the presence of glycerol or protein aggregates. Two different mechanisms are responsible for the ThT signal quenching-the ThT hydroxylation at basic pH and protonation of the nitrogen atom of the dimethylamino group at acidic pH. ThT assays should be carefully carried out at basic or acidic pH as strong pH dependence of ThT could be responsible for misinterpretation and false positive/negative experimental results. The potential unsuitability of ThT as a probe in solutions with high pH (>9) has been shown.
Related Concept Videos
Variables Affecting Phosphorescence and Fluorescence
Titration of a Weak Acid with a Weak Base
As a result, there is no simple...
Photoluminescence: Applications
Fluorescence and Phosphorescence: Instrumentation
Indicators
Substituent Effects on Acidity of Carboxylic Acids

