Terahertz absorption measurements of amino acids and peptides

Abstract

Absorption cross section was obtained for amino acids Lalanine and glycine, and peptides di- L-alanine, di-glycine, tri- L-alanine, and tri-glycine using terahertz time domain spectroscopy (THz-TDS). Power law characteristics of reduced absorption cross section was observed for all of the biomolecules whose exponent is ~2 for amino acids then decreases its value as the peptide chain increases in length. This shows the harmonic behavior of the low frequency vibrations of amino acids as well as the extent of anharmonic coupling of vibrational modes when the peptide chain is increased.