Dissociation constant (Kd)

Definition

The dissociation constant (Kd) is a measure of the affinity between a ligand and a receptor, representing the equilibrium concentration at which half of the receptor binding sites are occupied by the ligand. A lower Kd value indicates a higher affinity between the ligand and receptor.

5 Must Know Facts For Your Next Test

1. Kd is expressed in units of concentration, typically mol/L.
2. A low Kd value implies strong binding affinity, whereas a high Kd value implies weak binding affinity.
3. Kd is related to the equilibrium constant (Keq) for the binding reaction: $K_d = \frac{1}{K_{eq}}$.
4. In biochemical contexts, Kd is often used to describe interactions between enzymes and substrates, or antibodies and antigens.
5. Kd can be determined experimentally through techniques like surface plasmon resonance or isothermal titration calorimetry.

Review Questions

Related terms

Equilibrium Constant (Keq): A measure of the ratio of concentrations of products to reactants at equilibrium for a reversible reaction.

Ligand:

A molecule that binds specifically to another molecule, usually a larger one such as a protein.

Binding Affinity: The strength of the interaction between a ligand and its target molecule.