Computational modeling of the optical rotation of amino acids: An 'in silico' experiment for physical chemistry

• Autores: Scott Simpson, Eva Zurek, Jochen Autschbach
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 90, Nº 5, 2013, págs. 656-660
• Idioma: inglés
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• Resumen

  • A computational experiment that investigates the optical activity of the amino acid valine has been developed for an upper-level undergraduate physical chemistry laboratory course. Hybrid density functional theory calculations were carried out for valine to confirm the rule that adding a strong acid to a solution of an amino acid in the l configuration renders the optical rotation more positive. Correspondingly, if the optical rotation becomes more negative, the amino acid is of the d configuration. The students employed the open-source molecular editor Avogadro to build the molecules, conduct conformer searches, and calculate the energies of the conformers with a molecular mechanics force field. Subsequent geometry optimizations and optical rotation calculations were performed with a quantum chemistry program, using the WebMO graphical interface. The role of the solvent in stabilizing the zwitterionic form of an amino acid was investigated.