Molecular recognition and catalysis controls the life processes. Our research is focused on the design of molecules inspired by nature, especially new catalysts and molecules that interact with biomolecules specifically and with high affinity. While our research began with polypeptides and synthetic proteins based on the common amino acids, we have become more interested in polypeptides where the side chains have been modified by organic synthesis. Polypeptides carrying non-natural amino acids fold in novel ways, catalyze chemical reactions efficiently and bind proteins with high affinity and selectivity. They are of considerable interest for applications in drug development and diagnostics.