Spectroscopic Determination of Tryptophan and Tyrosine in Proteins

Abstract

A rapid method for the determination of tryptophan in proteins is presented. It is based on absorbance measurements at 288 and 280 mμ of the protein dissolved in 6 m guanidine hydrochloride. Blocked tryptophanyl (Nacetylltryptophanamide) and tyrosyl (glycylltyrosylglycine) compounds were selected as model substances to represent the absorbance of the two chromophores in proteins. Tyrosine is measured simultaneously with tryptophan but with much less precision in proteins where most of the absorption is due to tryptophan. An independent procedure of tyrosine analysis is presented also which is based on its ionization in alkali. © 1967, American Chemical Society. All rights reserved.