Many "new generation" peptidomimetics are designed to present amino acid side chains only; they do not have structural features that resemble peptide main chains. These types of molecules have frequently been presented in the literature as mimics of specific secondary structures. However, many "side-chain only" peptidomimetics do not rest in single conformational states, but exist in a limited number of freely interconverting forms. These different conformations may resemble different secondary structures, so referring to them as, for instance, turn- or helical-mimics understates the ways they could adapt to various binding situations. Sets of scaffolds that can be used to mimic aspects of nearly every secondary structure, i.e. universal peptidomimetics, can be constructed. These may assume a privileged place in library design, particularly in high throughput screening for pharmacological probes for which binding conformations, or even the target itself, is unknown at the time the library is designed (critical review, 101 references).
