mass photometry

Mass photometry (MP) is a fast, label-free way to check protein oligomerization, heterogeneity, and complex formation using only ~10 µL of sample at 10–50 nM. It detects single molecules as they land on a glass coverslip, converts scattering contrast to molecular mass using standards (e.g., BSA), and outputs a histogram where peaks reveal monomers, dimers, higher oligomers, and aggregates with their relative abundance. MP supports quick go/no-go decisions and sample quality control before cryo-EM, crystallography, or binding studies. Good prep (clean coverslips, calibration, filtering/spinning, and ≥90–95% purity) keeps peaks sharp and interpretable. Know the limits: <30 kDa proteins and complexes may be missed.