Changes in the Short Wavelength Absorption Spectrum of Tyrosine as a Result of its Participation in Peptide, or Similar Bonds

1 The perturbation of the spectrum of free tyrosine that occurs when this amino acid is combined to other amino acids or in the form of acetyl derivative, acetyl derivative amide or acetyl derivative ethyl ester was studied. 2 The difference spectrum of each compound was obtained by measuring the absorbance of its solution against that of a mixture of its component free amino acids. 3 A red-shift of the 2,400 A absorption band, in 0.1 M NaOH, or 2,230 A, at pH 7, was clearly detected. 4 Maximum perturbation is produced when tyrosine has both its amino and carboxyl groups involved in peptide bonds.