Rebinding Leads to Decreased Off Rates

The display of a receptor or ligand at high density can result in its partner exhibiting increased functional affinity, even if multipoint binding does not occur. The increase in apparent affinity can be rationalized by modeling the binding event as a two-step process. In the first phase, receptor and ligand form a transitory encounter complex. The second stage involves the transitory species proceeding to generate a stable complex or dissociating as a result of nonproductive binding (Fig. 5B). In the case of a multivalent partner, the probability of rebinding increases and that of dissociation decreases. Because the off-rates are slower for such an interaction, the observed

A. The Chelate Effect tiil

C. Receptor Clustering

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E. Steric Interference mi

Figure 5 Modes of multivalent binding.

B. Statistical Effect

D. Subsite Binding tili

F. Polyelectrolyte Effect o ®o ©0

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