FORCE-FIELD AND NORMAL-COORDINATE CALCULATIONS FOR GLUTAMIC-ACID

The MNDO-scaled harmonic force field of glutamic acid is obtained in t he space of a set of non-redundant local-symmetrized internal coordina tes. A set of scaling factors is transferred from aspartic acid. The t heoretical vibrational frequencies for the fundamentals are successful ly compared with the observed values, and the frequencies of the N-15 and d-4 isotopic derivatives are also calculated and compared with the experiments. These results and the description of the normal modes fo llowed by mean of the potential energy distribution, agree with the pr evious assignments proposed for most of the observed bands, showing an extensive coupling among the bending and skeletal stretching coordina tes.