 Solution

The main particles are approximately 120 kDa in both conditions. With 30 kDa per protein subunit, this supports a tetramer:The small peptide contribution is not clearly resolved as a separate mass increase at this scale. Together with the microscopy, the results support a conformational change of an existing tetramer, rather than a large change in oligomer number. Mass photometry reports the scattering-derived mass distribution of detected particles; it does not by itself identify which conformation a particle adopts or count small bound ligands precisely.