Kinetics of Protein Binding describes the interaction between a drug (D) and a protein (P) to form a drug-protein complex (DP).
This process follows a reversible equilibrium:
Rate of Drug-Protein Binding
The association and dissociation of drug-protein binding follow the rate equation:
where:
[D] = Free drug concentration
[P] = Free protein concentration
[DP] = Drug-protein complex concentration
[Kon] = Rate constant for drug-protein association
[Koff] = Rate constant for drug-protein dissociation
Equilibrium Dissociation Constant (K_D)
At equilibrium, the dissociation constant (Kd) is given by:
A lower Kd indicates stronger drug-protein binding.
A higher Kd suggests weaker binding.
Fraction of Bound and Unbound Drug (Kinetics of Protein Binding)
Bound Drug Fraction ()
The fraction of the drug that is bound to the protein is:
where:
(i.e., the total drug concentration is the sum of free and bound drug concentrations).
Unbound Drug Fraction ()
The fraction of the drug that remains unbound is:
Since the total drug must be either free or bound:
