B-subunit pentamers are expected to interact simultaneously with more than one copy of their target glycan in the glycocalyx. To quantify the aggregate binding strength of such multivalent interactions, we performed protein titration experiments on model glycocalyces by SE. Figure provides representative data for the binding of STxB to a model glycocalyx made from (HA-g-Gb3)-B. It can be seen that binding reached equilibrium within a few minutes at all concentrations. The unusual transient maxima in binding at the two highest STxB concentrations (2 and 4 μM) are likely due to the scattering of the light while the protein mixture in the SE chamber was homogenizing. Most of the protein was rapidly released upon rinsing in plain working buffer, confirming the reversibility of binding already seen by QCM-D (Figure ).