Recognition forces in ligand-protein complexes: blending information from different sources

A variety of ligands interact with proteins in many biological processes; shape complementarity, electrostatic forces and hydrophobicity are the main factors governing these interactions. Although this is accepted by the scientific community, confusion about the significance of certain terms (e.g. hydrophobicity, salt bridge) and the difficulty of discussing the balance of acting forces rather than their single contributions, are two of the main problems encountered by researchers working in the field. These difficulties are sometimes enhanced by the unskilled use of informatics tools, which give great help in understanding the topic (especially from the visual standpoint), but only if used critically. After explaining some general chemical concepts, the commentary discusses the main forces governing ligand-protein interactions, focusing on those generating confusion among scientists with different backgrounds. Three examples of ligand-protein interactions are then discussed to illustrate the advantages and drawbacks of some in silico tools, highlighting the main interactions responsible for complex formation. The same examples are used to point out the limits in separating forces that are mandatory for occurrence of a given interaction and additional forces.