Dissociation constant

Dissociation Constant is a specific type of equilibrium constant that measures the propensity of a larger object to separate (dissociate) reversibly into smaller components, as when a complex falls apart into its component molecules, or when a salt splits up into its component ions.

Overview

The dissociation constant is usually denoted by Kd and is used to describe the interaction between two molecules such as a protein and a ligand. The lower the dissociation constant, the more tightly bound the ligand is, or the higher the affinity between ligand and protein.

Calculation

The dissociation constant is the inverse of the association constant (Ka) and can be calculated using the equation:

Kd = [A][B]/[AB]

where [A] and [B] are the molar concentrations of the dissociated components and [AB] is the molar concentration of the complex.

Applications

Dissociation constants are used in many areas of chemistry and biochemistry, including in the design of drugs and in the study of proteins and other macromolecules.

See also

• Chemical equilibrium
• Equilibrium constant
• Acid dissociation constant
• Base dissociation constant
• Protein-ligand binding