STRUCTURAL AND SPECTROSCOPICAL STUDY OF GLUTAMIC-ACID IN THE NON-ZWITTERIONIC FORM

The molecular structure of glutamic acid in the non-zwitterionic form has been optimized by using the semiempirical MNDO and AM1 methods and an ab initio calculation at the 4-31G level. The results were compare d with previous reported data for other amino acids, The ab initio opt imized structure was used as the starting point for a further force he ld calculation, and vibrational frequencies and theoretical assignment s were thus obtained. In order to compare these results with experimen ts, the FT-IR spectrum of glutamic acid in an argon matrix was recorde d and the measured frequencies were successfully compared with theoret ical values, which were previously scaled by using a set of scaling fa ctors.