This Fidabio poster demonstrates how small-molecule binding to a membrane protein can be characterised directly in solution, without labelling or immobilization. Flow Induced Dispersion Analysis (FIDA) was used to measure changes in hydrodynamic radius (Rh) and Binding Related Intensity Change (BRIC) from intrinsic fluorescence to detect binding between small molecules and a detergent-solubilised membrane protein, using only ~1.4 µL of protein per titration. When neither Rh nor BRIC changed, FIDA-based urea unfolding assays revealed a shift in Gibbs free energy, confirming binding that produced no detectable size or intensity signal. It is an example of using FIDA to characterise small-molecule–protein interactions and conformational changes in membrane protein systems.