Cooperative binding

In biochemistry, a macromolecule has cooperative binding if when binding a ligand, the affinity of the ligand for the molecule changes depending on the amount of ligand already bound. A macromolecule is said to have positive cooperativity if the binding of ligand increases affinity for the ligand, and negative cooperativity if the affinity for the ligand decreases as more ligand is bound. A macromolecule is noncooperative if the amount of ligand bound does not affect the binding affinity at all. In this final case, the macromolecule is described as having hyperbolic binding behavior (because a plot of ligand bound as a function of ligand concentration traces a hyperbola).