Pseudo-dissociation rates were obtained by injecting a pre-mixed 1:1 solution of QD-DiMan and labeled lectins into a binding buffer containing excess of free D-mannose. A 10 6 QD molar equivalent of D-mannose was found to effectively compete with lectin-QD-DiMan binding (SI, Fig. ), thus this ratio was used in all dissociation experiments. The presence of free mannose greatly reduces the amount of lectins bound to the QD, leading to a decrease of dye FRET signal together with the simultaneous recovery of the QD fluorescence, and hence a decrease of FRET ratio (Fig. ). Notably, a rapid decay in FRET ratio is observed by all proteins, demonstrating that QD-DiMan must be specifically binding at the glycan binding sites in all three lectins, and not due to non-specific interactions (Fig. ). These FRET decay curves were fitted by a pseudo-first order rate equation, Eq. 4, (see SI, section 6.3 for derivation) as the change in mannose concentration is negligible. Here, 𝑘 𝑜𝑓𝑓 ′ is the apparent pseudo-first order dissociation rate coefficient.