CONFORMATIONAL BACKBONE DYNAMICS OF THE CYCLIC DECAPEPTIDE ANTAMANIDE- APPLICATION OF A NEW MULTICONFORMATIONAL SEARCH ALGORITHM-BASED ON NMR DATA

A general procedure for the analysis of biomolecular structures by NMR in the presence of rapid conformational dynamics has been applied to the study of the cyclic decapeptide antamanide. Two-dimensional experi ments, relaxation measurements in the rotating frame, and homo- and he teronuclear coupling constant determinations have been used to charact erize the dynamic properties of the molecule, in combination with a no vel search algorithm for investigating multiconformational equilibria. Direct evidence for the presence of a conformational exchange process with an activation energy of approximately 20 kJ mol-1 and an exchang e lifetime of approximately 25 mus at 320 K has been obtained from rot ating frame relaxation measurements. This evidence is combined with th e information derived from the multiconformational search algorithm ME DUSA to propose sets of structures that coexist in a dynamic exchange equilibrium.