Comparison of Raman and FTIR spectra of amino-acids

In this project, we have been measuring and generating large sets of Raman and FTIR spectra (and other optical-based techniques) of powdered and aqueous samples of a series of amino- acids and proteins at different concentrations. Here we present spectra of Bovine Serum Albumin (BSA) protein solution and selected amino-acids (l-alanine, l-arginine, l-leucine, l-phenylalanine, l-proline, l-serine). The measured spectra show a series of peaks over 500-3500 cm-1 range, including those of water (~1640 cm-1 HOH bend; ~3200 cm-1 OH stretching band). More significantly, we identified four distinct spectral peaks (~1000 cm-1, ~1467 cm-1, ~2900 cm-1, and ~2950 cm-1) to be associated with the vibrational modes of amino acids and BSA proteins. The intensities of these peaks tend to increase with the biomolecular concentration while those of the water tend to decrease, indicating a systematic reduction of water content. We applied Principal Component Analysis and Intensity Correlation Analysis methods to analyze possible changes of the profiles of the observed peaks with changes of the biomolecular concentration.