| Abstract
| - The natural optical activity of two chiral amino acids, alanine and proline, has been calculated using Hartree−Fock and density-functional theory with the Becke three-parameter Lee−Yang−Parr (B3LYP) functionalemploying analytical response theory. The dependence of the optical activity on the molecular conformationin the gas phase was investigated. In the case of proline, calculations were also carried out for the protonatedand deprotonated molecules. The increase of the optical rotation of proline with increasing pH, foundexperimentally, is reproduced by our calculations. The optical rotation of both amino acids is found to bevery sensitive to the molecular geometry, to the extent that it changes sign for the different conformers. Foralanine, the sign of the optical rotation varies with the rotation of the amino or carbonyl groups.
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