Conformational Analysis of Phenylalanine and its Cobalt(III) Complex Using Quantum Mechanical Calculation

Abstract

Some conformational isomers of amino acids like phenylalanine and aspartic acid play a significant role in the reaction and the function of the amino acid in the biological system. The population of the conformational isomers has been so far determined by a use of infrared spectroscopy and proton magnetic resonance. However, recently, computer chemistry is making great advances according to the progress of personal computers (e.g. windows machine) and the appearance of high performance software comercially available. Now we can use these computers and software for our research. In this work, we optimized structures of a neutral molecule, an anion, a cation and a cobalt(III) complex of phenylalanine using ab-initio calculation and also DFT calculation. Stability and population of each conformational isomer were discussed by estimating the energy value of the optimized structure. The population of the conformational isomers was consistent with that obtained by the experimental method (NMR). Both methods indicated that the isomer having a benzyl group trans to a carboxyl group is the most stable.