Effect of the Environment on Vibrational Infrared and Circular Dichroism Spectra of (S)-Proline

The infrared and vibrational circular dichroism of proline in water solution are investigated ab initio employing density functional theory and the integral equation formalism (IEF) version of the polarizable continuum model (PCM). Three solvent models are exploited to evaluate solvent effects in the 1000–2000 cm1 frequency range: a pure implicit continuum approach, a pure explicit model (limited to three solvent molecules), and a combined specific/continuum approach. Effects on spectra arising from different protonation states (neutral, zwitterionic, cationic, and anionic) are analyzed