Time dependent density functional theory modeling of specific rotation and optical rotatory dispersion of the aromatic amino acids in solution

Time Dependent Density Functional Theory (TDDFT) along with the COnductor-like Screening MOdel (COSMO) has been applied to model the specific rotation at 589.3 nm and the optical rotatory dispersion (ORD) of the aromatic amino acids phenylalanine, tyrosine, histidine, and tryptophan. Solution structures at low, neutral, and high pH were determined. Both the anomalous dispersion absorbing (resonance) region and the lower energy (transparent) region of the ORD of the compounds were modeled. Linear response calculation of the specific rotation and ORD as well as Kramers-Kronig transformations of calculated circular dichroism spectra to model resonant ORD were compared with experimental data from the literature.