Physiological, pathophysiological and artificial ligands such as antibody fragments, protein domains, and peptides can be isolated from combinatorial libraries. The basis thereof is comprised by the generation and selection of particular libraries. Exemplary, recombinant immune repertoire libraries are generated from suitable donor-derived immune cells and thus reflect the natural repertoire of these donors. This allows for molecular analyses of individual immune responses. Alternatively, synthetic libraries build independently of individual donors enable a de novo isolation of ligands against all kinds of target structures.

One of the fundamental technologies for selection of such protein or peptide libraries relies on the presentation on the surface of phages, the so called Phage Display, and iterative enrichment of binders via interaction with the target structures of interest.

Obtained molecules provide unique information about the molecular nature and specificity of the interaction.