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Vibrational Spectroscopic Study of L-Phenylalanine: Effect of pH

Volume 55, Number 7 (July 2001) Page 901-907

Olsztynska, S.; Komorowska, M.; Vrielynck, L.; Dupuy, N.

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 pKa 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.