Protein Ligand

In biochemistry, a protein ligand is an atom, a molecule or an ion which can bind to a specific site (the binding site) on a protein. Alternative names used to mean a protein ligand are affinity reagents or protein binders. To date, antibodies are the most widely used protein ligands in life-science investigations, however, other molecules such as protein scaffolds, nucleic acids, peptides are also being used.

In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from covalent to ionic. Furthermore, the metal-ligand bond order can range from one to three. Ligands are viewed as Lewis bases, although rare cases are known to involve Lewis acidic "ligand."