Conformation and Biological Activity of Cyclic Peptides

Abstract Cyclic peptides containing biologically active hormone sequences are suitable models for studying conformation‐activity relationships. In such models the usual flexibility of peptide chains is reduced by their cyclic arrangement. However, conformational analysis of such systems by experimental means is possible only if a single conformer predominates at equilibrium, and criteria for this are put forward. NMR spectroscopic methods, including many recent advances, are discussed in relation to their ability to contribute to peptide conformational analysis.