Blocking experiments, using molecules known to block the interaction, are also useful negative
controls. In contrast, if no binding is detected it becomes necessary to run positive controls to
whether this reflects the absence of an interaction, a very low affinity, or an artefact
resulting from defective ligand or analyte. The ligand is readily assessed by showing that it can bind
to one or more mAbs or additional analytes should they exist. The analyte can be tested by injecting
it over a surface with either a known interacting ligand or or mAb immobilised to the surface.
6.2. Qualitative comparisons using a multivalent analyte
The binding of a multivalent analyte can be heavily influenced by the level of immobilised ligand,
since the latter will influence the valency of binding. Thus when comparing the binding of a
multivalent analyte to different ligands it is important that these ligands are immobilised at
comparable surface densities.