L-Valine and L-Proline - Solid-State IR-LD Spectroscopic Study

Spectral investigation including IR-characteristic bands assignment of the amino acids zwitterions L-Valine (LVal) and L-Proline (L-Pro) was carried out by linear-dichroic infrared (IR-LD) spectroscopy of oriented solid sample as a nematic liquid crystal suspension. The obtained experimental IR-LD results (transition moment directions) were compared with known crystal X-ray data for molecules orientation in the unit cells of the studied compounds, confirming the applicability of the used spectral method for structural determination. The influence of the protonation on the IR-spectroscopic patterns of the both amino acids is discussed.