Vibrational Spectroscopic Study of l-Phenylalanine: Effect of pH

Abstract

Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectra of l-phenylalanine in aqueous solution were recorded in the pH range 0–13. The vibrational molecular spectroscopic study of this amino-acid, a well-known component of human tissue, showed that l-phenylalanine undergoes structural changes under the influence of pH. Characteristic bands of each ionic species were highlighted and the p Ka values were determined from IR measurements by using an intensity ratio method. ATR-FTIR spectroscopy appears to be a powerful tool for obtaining valuable information on the building blocks of proteins and for measuring tissue damage in aqueous environments.