Label-free tracking and mass measurement of single protein complexes on lipid bilayers

Biomolecular interactions in and on lipid bilayers are critical for a number of cellular processes, but are difficult to robustly and stoichiometrically quantify. Approaches to visualise and track single proteins on lipid bilayers mostly rely on fluorescent labelling, which has inherent limitations in observation times and the ability to resolve different species and oligomeric states, making the quantitative and stoichiometric characterisation of biomolecular interactions challenging. Here, we demonstrate dynamic mass photometry, a method for label-free imaging, tracking and mass measurement of individual membrane-associated proteins on supported lipid bilayers.