Data from: A mix-and-click method to measure amyloid-β concentration with sub-micromolar sensitivity

Aggregation of amyloid-β (Aβ) protein plays a central role in
Alzheimer's disease. Because protein aggregation is a
concentration-dependent process, rigorous investigations require accurate
concentration measurements. Owing to the high aggregation propensity of Aβ
protein, working solutions of Aβ are typically in the low micromolar
range. Therefore, an ideal Aβ quantification method requires high
sensitivity without sacrificing speed and accuracy. Absorbance at 280 nm
is frequently used to measure Aβ concentration, but the sensitivity is low
with only one tyrosine and no tryptophan residues in the Aβ sequence. Here
we present a fluorescence method for Aβ quantification using
fluorescamine, which gives high fluorescence upon reaction with primary
amines. We show that, using hen egg white lysozyme as a standard,
fluorescence correlates linearly with primary amine concentration across a
wide range of fluorescamine concentrations, from 62.5 to 1000 µM. The
maximal sensitivity of detection is achieved at a fluorescamine
concentration of 250 µM or higher. The fluorescamine method is compatible
with the presence of dimethyl sulfoxide, which is commonly used in the
preparation of Aβ oligomers, and limits the use of absorbance at 280 nm
due to its high background reading. Using aggregation kinetics, we show
that the fluorescamine method gives accurate concentration measurements at
low micromolar range and leads to highly consistent aggregation data. We
recommend the fluorescamine assay to be used for routine and on-the-fly
concentration determination in Aβ oligomerization and fibrillization
experiments.