Question

5. Define M, L, M·L for the following binding reaction: M + L ↔ M·L. What is the dissociation constant, K_d, for this reaction? What are the typical units of K_d? Which has higher affinity, an interaction with a K_d = 1 mM (10^-3 M) or an interaction with K_d = 1 nM (10^-9 M) How is K_d operationally defined?

Answer 1

5. Ans-

Given that,

M + L <====> ML,

For the above reactions,

M is free macromolecule, L is free ligand, and ML is macromolecule-ligand complex

The dissociation constant, Kd for this reaction is,

Kd= [M]_eq[L]_eq/[ML]_eq

The unit of Kd is molarity( M)

An interaction with a Kd= 1mM is less affinity than an interaction with Kd=1nM. Because the lower the value of Kd then the tighter the binding and the higher value of Kd means the looser the binding.

Dissociation constant, Kd is K d {\displaystyle K_{d}}an equilibrium constant for dissociation of the products to reactants