Ligands

A ligand is simply any molecule which interacts with any given molecule, often a protein molecule. This vast range of size and type of ligand makes it difficult to understand and draw conclusions about their behaviour and biophysical properties, including the nature of their interactions with proteins.

In the context of protein function, a ligand is simply a molecule that is capable of a (usually reversible) non-covalent interaction with the protein which modulates the protein’s biological role in some controllable manner. The non-covalent nature of these interactions means that they have some similarities with the interactions that hold hold together the secondary secondary structure of a protein, namely; hydrogen-bonding, van der Waals and charge interactions in particular are important for ligand binding, as is complementarity with the active or binding site. These interactions are what provides the specificity of a particular ligand for a given protein.