Ligand Binding to Macromolecules
Another aspect of the notion of chemical equilibrium is that concerning the binding of chemical species called ligands on macromolecules, especially on proteins. Such processes are the rule rather than the exception in biological systems. Thus, for example, ligands bind to a variety of receptors such as enzymes, antibodies, DNA and membrane-bound proteins. Protein binding also plays an important role in pharmacology. For a long-time, the interactions have been envisioned as being the result of the fact that the protein was topologically complementary to the stereochemistry of the substrate. Over the years, the origin of the interactions has evolved. Now, one knows that beyond the stereochemical aspect, the formation of hydrogen bonds, interactions dipole-dipole, and the formation of salts between the ligand and the interacting groups of the binding site also intervene.