European Journal of Biomedical and Pharmaceutical Sciences

COMPARATIVE STRUCTURAL AND VIBRATIONAL STUDY ON THE MOLECULAR STRUCTURE OF THREONINE AND TYROSINE BY AB INITO AND DENSITY FUNCTIONAL THEORY

Santosh Kumar Srivastava* and Vipin B. Singh

ABSTRACT

A brief structural and vibrational study has been performed on the molecular structure of two well known amino acids threonine and tyrosine. The equilibrium geometry, harmonic vibrational frequencies, and infrared intensities were calculated by the ab initio HF and density functional B3LYP method employing 6-311++G(d,p) and Aug-cc-pVDZ as the basis sets. A detailed interpretation of the infrared spectra of threonine and tyrosine is reported in the present work. The similarities and differences between the vibrational spectra of the two molecules studied have been highlighted. The calculations are in agreement with experiment. The theromodynamic calculations related to the title compounds were also performed at HF and B3LYP levels of theory employing 6-311++G(d,p) and Aug-cc-pVDZ basis sets respectively. The FTIR spectra of tyrosine were recorded in solid and liquid phases respectively.

Keywords: FT-IR spectra, Ab initio and DFT calculations, Threonine and Tyrosine, Vibrational study.