# Relation between binding free energy and solubility

1. Jan 16, 2012

### Chirag740

Suppose we have a ligand binding to a receptor in solvent medium. I am interested to know whether there is any relation between "Binding free energy" and "Solubility".

Extemely sorry if I posted my question in the wrong section. I'd be glad if anyone could help me out with this.

Regards,
Chirag V. Vora
Department of Pharmacoinformatics,
Block - A, Bioinformatics Infrastructure Facility,
National Institute of Pharmaceutical Education and Research (NIPER)
Sector 67, S.A.S. Nagar,
Punjab (INDIA) - 160 062

2. Jan 16, 2012

### DrDu

That's not only a question of energetics but even more of entropy.
The equilibrium constant for dissociation can be calculated from
$\Delta G=\Delta H -T \Delta S \approx \Delta U -T \Delta S$
where $\Delta U$ is the dissociation energy per mole and in solution is practically equal to the enthalpy change,
and $\Delta S$ the entropic change due to dissociation.
The equilibrium constant K is
$K=\exp(\Delta G/RT)$

$\Delta G$ is the free energy of binding, so the relation is quite direct.