Cα Proton Research Articles

Nmr analyses of conformations of linear peptides in solution

AbstractImportant aspects in detailed nmr analyses of the conformations of linear peptides are discussed using enkephalin and the α‐mating factor of Saccharomyces cerevisiae as examples. The cationic, dipolar, and anionic forms in dimethyl sulfoxide solution may be identified by ir analyses. Because of the electrostatic interaction between the N‐ and C‐terminal groups, the dipolar form of enkephalin takes the folded conformation, as well as extended conformation(s), in dimethyl sulfoxide solution. Such conformational equilibrium is responsible for anomalous temperature dependences and solvent‐composition dependences of the amide and Cα proton chemical shifts. Active analogs, enkephalinamide and enkephalinol, take extended conformation(s) in solution. These opioid peptides probably take a specific active conformation upon binding with a receptor. For the α‐mating factor and active peptide analogs in aqueous solution, a folded conformation with two βturn structures is responsible for the biological activity.