The intrinsic fluorescence detector is sensitive enough to detect species of protein that do not contain tryptophan. Here, down to 5 μM of monomeric unlabelled WT αSyn (ε 280 = 5,960 M -1 cm -1 ; four tyrosine residues) could be detected. The quantification of monomer concentration enables straightforward and reliable data normalization. Moreover, absolute concentration of monomer can be obtained if it can be independently demonstrated that the samples are fully monomeric at the highest denaturant concentrations. Otherwise, a calibration curve with known monomer concentrations can be used.