Design of bioactive and structurally well-defined peptides from conformationally restricted libraries

Libraries of peptides and proteins can be categorized according to the function of their origin in gene- and syntheticbased libraries. Both kinds of libraries have the potential to generate the same grade of molecular diversity, although the limits imposed by the synthetic methods have been lately a matter of discussion. However, the use of synthetic strategies allows incorporation of non-natural amino acids. The development of conformationally restricted synthetic peptide libraries can be considered as a point of convergence of the two methodologies. In these libraries the diversity is grafted into scaffolds that are defined by stable secondary structural motifs, and the deconvolution protocols can be directed towards the identification of biologically active molecules and the analysis of determinants of folding of protein domains.