
Binding constant
Encyclopedia
The binding constant is a special case of the equilibrium constant
. It is associated with the binding and unbinding reaction of receptor (R) and ligand (L) molecules, which is formalized as:
.
The reaction is characterized by the on-rate constant
and the off-rate constant
, which have units of 1/(concentration time) and 1/time, respectively. In equilibrium, the forward binding transition
should be balanced by the backward unbinding transition
. That is,
,
where
,
and
represent the concentration of unbound free receptors, the concentration of unbound free ligand and the concentration of receptor-ligand complexes. The binding constant, or the association constant
is defined by
.
An often considered quantity is the dissociation constant
, which has the unit of concentration. For the binding of receptor and ligand molecules in solution, the molar Gibbs free energy
, or the binding affinity is related to the dissociation constant
via
,
in which
is the ideal gas constant,
temperature and the standard reference concentration
= 1 mol / L.


The reaction is characterized by the on-rate constant





where





An often considered quantity is the dissociation constant

Gibbs free energy
In thermodynamics, the Gibbs free energy is a thermodynamic potential that measures the "useful" or process-initiating work obtainable from a thermodynamic system at a constant temperature and pressure...



in which


