ABSTRACT
All living systems are based on interactions between molecules, and the recognition that takes place in these interactions. The formation of complex structures, such as membranes, DNAduplexes, and whole cells, is essentially a consequence of a multitude of such binding processes. In contrast to the strong (covalent) forces keeping single molecules together in de¢ned species, these complexes are normally maintained by weaker binding forces, leading to dynamics in their formation and breakdown. This dynamic property is a prerequisite for the functioning of many biological processes, and the possibility of rapid organization betweendi¡erent units is the foundation of such diverse reactions as DNA replication, enzymatic catalysis, and protein biosynthesis. Molecular interactions are furthermore a basis for chemical and biological information. All processes comprising molecular interactions, such as hormone responses and cell adhesions, are a consequence of ‘‘weak’’ communications between molecules or groups of molecules. In addition, the identi-¢cation of self-and non-self in immune systems is based on themolecular recognition of identity markers. This molecular interplay is thus responsible for the expression of life per se.
