Refinement of the Molecular Structure of Actinomycin D by Energy Minimization

The atomic coordinates of actinomycin D obtained by x‐ray analysis by Sobell et al. have been refined to fit a set of standard bond lengths and bond angles using a least squares procedure and a conformational energy minimization technique. The computationally refined structure shows greater similarity between the conformations of the two pentapeptide rings and an improved dyad symmetry, compared to the x‐ray structure. The refined structure is compared with NMR data and with the structure proposed by De Santis et al. The energy calculations also provide information about the conformational features of cis proline residues in polypeptide chains.