AbstractThe degrees of conformational freedom of polyL–Dβ‐helical chain are analyzed consistent with the helical parameters of gramicidin A structure. From conformational energy calculations, “helical librations” that can be sustained by this structure are described and the energy of libration as a function of the cavity size is presented. Two different modes of conformational change are identified corresponding to librations of allL–D‐peptide units or allD–L‐peptide units while retaining the helical parameters. Such helical librations are considered relative to conformational perturbations due to the presence of an io