Theoretical Comparative Study of the Structure, Dynamics and Electronic Properties of Two Allyl Molecules: S-allyl cysteine (SAC) and S-allyl mercaptocysteine (SAMC)

Emine Deniz Calisir¹, Sakir Erkoc^{1 (*),} Handan Yildirim², Abdelkader Kara², Talat S. Rahman², Mahmut Selvi³, Figen Erkoc³

¹Department of Physics, Middle East Technical University, 06531 Ankara, Turkey, ; e-mail: erkoc@erkoc.physics.metu.edu.tr ; Tlf.: +90 312 210 3285; Fax: +90 312 210 1281

²Department of Physics, Kansas State University, Manhattan, KS 66506, USA

³Department of Biology Education, Gazi University, 06500 Ankara, Turkey

 Abstract: The structural, dynamic and electronic properties of two allyl molecules (S-allyl cysteine and S-allyl mercaptocysteine) have been investigated theoretically by performing semi-empirical molecular orbital (AM1 and PM3), ab initio (RHF) and density functional theory calculations. The geometry of the molecules have been optimized, the vibrational spectra and the electronic properties of the molecules have been calculated in their ground states in gas phase. For each of the two molecules, we found that the optimized geometries resulting from calculations based on the three levels of accuracy, to be very similar. However, we found that an accurate description of the vibrational properties of these molecules necessitates calculations at the ab initio level. We also found electronic structures of the molecules to be satisfactory when performed at the DFT level.

 Keywords: S-allyl cysteine, S-allyl mercaptocysteine, antioxidant, garlic, semi-empirical method, ab initio calculation, density functional method

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