Multivalent and multispecific receptors were constructed using the C-terminal SH3 domain of the human adaptor protein Gads and the synthetic protein Prb, as described previously23 (link). Multivalent and multispecific ligands incorporated the SH3 binding peptide (SBP) from the Gads cognate ligand SLP-7648 (link), as well as the synthetic designed Prbbinding DARPin, Pdar49 (link). Association and dissociation kinetics between ligand and receptor constructs were quantified by surface plasmon resonance measurements on a Biacore S200 instrument.