Table 2.

Affinity constants for binding of HD exon 1 to MW1 Fab

Protein	Affinity constant,* μM
	KD1	KD2	KD3
HD-16Q	25.3	73.9	Not applicable
HD-25Q	14.0	78.7	≈29†
HD-39Q	2.2	65.2	≈7†
HD-46Q	1.5	37.5	≈5†

^*K_Ds determined from global fits of equilibrium-based biosensor data (at low, medium, and high ligand coupling density) to the best-fit bivalent or trivalent binding models (Fig. 3 c–f). 

^† K_D3 values are not well determined because they are sensitive to possible tetravalent (or higher valency) interactions that are not accounted for in our binding models, which lead to artefactually low values for K_D3. Lower values of K_D3 relative to K_D2 are not predicted by the linear lattice model unless there is positive cooperativity.