Fluorescence Quantum Yields of Tryptophan and Tyrosine

Abstract

Abstract Fluorescence quantum yields (Q) for tyrosine, tryptophan, and phenylalanine in water at 23° determined by the comparative method using a quinine standard were found to be 0.14, 0.13, and 0.024, respectively. Similar values were obtained with phenol as the standard. The numbers are much lower than those literature values which have been widely used to calculate protein fluorescence quantum yields. Possible reasons for the discrepancies are discussed. The quantum yields of isomeric tyrosines and fluorophenylalanines are also reported.