Selection of antibodies based on antibody kinetic binding properties.

Molecular evolution approaches to developing molecules with characteristics particularly suited for specific applications have become important tools in biomedicine and biotechnology. Not only is it possible to identify molecules with specificities that cannot easily be obtained by other means, but it is also possible to fine-tune in an efficient manner the properties for, in principle, any specified application. Attention has particularly been put into identifying molecules with specific reaction-rate and affinity properties. Depending on the intended application, the binding of a molecule to its target is desired to be long-lived or short-lived. In biosensors, it will generally be appropriate for the association between the ligand and its receptor to be rapid. However, the dissociation of the complex should also be fast to ensure a rapid response of the sensor to a changing environment, particularly in on-line systems. In contrast, stable, nondissociating interactions are favored when, for example, an antibody (Ab) is used for tumor imaging or tumor therapy. In conventional immunoassays, high affinity (and specificity) is often sought to ensure a high sensitivity of the assay. However, under conditions in which a high throughput rather than a highly sensitive format is necessary, it may be more important to have a rapid association rate and a rapid establishment of equilibrium of the assay system than simply to have an assay based on high affinity alone.