Basics of mass photometry 
Application Note

Mass Photometry (MP) is a label-free single-molecule technique based on optical detection of the scattering signal generated by a single particle at a glass-water interface. Mass photometry data is simply a series of images (Fig. 1). The weak scattering signal, from e.g. a single protein, is quantified against the background of orders of magnitude higher reflection at the interface. Thus, an average of N frames is taken and divided by the average of the N+1 subsequent frames revealing the differential signal, i.e. how much the signal changed in the presence of the molecule. The signal generated by a single molecule scales linearly with the mass of the molecule. For calibration, standard samples with known molecular weight can be used to assign mass to contrast. Hence, mass photometry accurately provides mass information for unknown samples.