FTIR and Raman Studies of Amino Acids and Proteins*

Fourier Transform Infrared (FTIR) and Raman spectra are powerful optical tools that can readily provide valuable insights into conformational and structural changes of complex molecules. As distinctive spectral fingerprints, we have been collecting and analyzing large sets of FTIR and Raman spectra of diverse biomolecules for designing and training multimodal, physics-based machine learning models for molecular identification, characterization, and classification.  In this study, we focus on amino acids, which are fundamental molecules for forming polypeptides and proteins relevant to diverse biological processes.  We present results of analysis of FTIR and Raman spectra of six amino-acids (Alanine, Arginine, Proline, Leucine, Serine, and Phenylalanine) solutions and solids as well as Bovine Serum Albumin (BSA) protein solution.  The spectra span the wavenumber range between 500-3500 cm^-1 from which we seek to determine relevant subsets that denote differences and similarities among the measured complex FTIR and Raman spectra, providing distinctive spectral features for each amino acid based on peaks/dips and peak/dip profiles. Further, we examine changes of the spectra with the increase of the concentration of amino-acids in water-based solutions, including “water-free” solid amino-acid powders.