FLUORESCENCE 2D AND 3D SPECTRA ANALYSIS OF TRYPTOPHAN, TYROSINE AND PHENYLALANINE

The analysis of fluorescence 2D and 3D spectra of tryptophan (Trp), tyrosine (Tyr) and phenylalanine (Phe) measured in physiological solution at 293 K are presented. The spectral characteristics of 2D fluorescence spectra of amino acids (AAc) are recorded in the following conditions: for Trp λex/λem=280/357, for Tyr 275/303 and for Phe 257/283 nm, and the 3D spectra of AAc recorded in λex=200–450 and λem=200–500 nm ranges are given. It has been revealed that 3D spectra of AAc are characterized by two strong excitation/emission peaks located at λex/λem=230/350 and 280/350 nm. The high energy emission (absorption) at 230 nm is due to n→π* or π→π* transitions of the carboxylic or amide group and low energy emission (absorption) at 280 nm is due to π→π* transition in the indole ring. In 3D spectra Rayleigh scattering peak and second-order scattering peak are identified as well.