Mechanism of fluorescence quenching of tyrosine derivatives by amide group

The difference between fluorescence lifetimes of the following amino acids: phenylalanine (Phe), tyrosine (Tyr), (O-methyl)tyrosine (Tyr(Me)), (3-hydr oxy)tyrosine (Dopa), (3,4-dimethoxy)phenylalanine (Dopa(Me)(2)) and their a mides was used to testify the mechanism of fluorescence quenching of aromat ic amino acids by the amide group. On the basis of the Marcus theory of pho toinduced electron transfer parabolic relationships between In k(ET) and io nization potentials reduced by energy of excitation (IP - E-0.0*) for the a bove-mentioned amino acids were obtained. This finding indicates the occurr ence of photoinduced electron transfer from the excited chromophore group t o the amide group. (C) 2001 Elsevier Science B.V, All rights reserved.