Premium
PHOTOKINETIC AND PHOTOPHYSICAL MEASUREMENTS OF THE SENSITIZED PHOTOOXIDATION OF THE TRYPTOPHYL RESIDUE IN N‐ACETYL TRYPTOPHANAMIDE AND IN HUMAN SERUM ALBUMIN
Author(s) -
Reddi E.,
Lambert C. R.,
Jori G.,
Rodgers M. A. J.
Publication year - 1987
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1987.tb05385.x
Subject(s) - rose bengal , chemistry , human serum albumin , residue (chemistry) , photochemistry , quantum yield , covalent bond , fluorescence , indole test , tryptophan , aqueous solution , quenching (fluorescence) , methylene blue , stoichiometry , hematoporphyrin , stereochemistry , organic chemistry , chromatography , biochemistry , amino acid , catalysis , photocatalysis , quantum mechanics , photodynamic therapy , physics
— The photosensitized oxidation of 10–100 μ M N ‐acetyl‐L‐tryptophanamide (NATA) in neutral aqueous solution and in the presence of various dyes proceeds by a pure O 2 ( 1 Δ g )‐involving mechanism. Incorporation of the tryptophyl (Trp) residue into the polypeptide chain of human serum albumin (HSA) has no influence on the mechanism and efficiency of Trp photooxidation when sensitized either by methylene blue, a non‐binding dye, or by rose bengal, a dye that gives non‐covalent 1: 1 complexes with HSA. This is due to the location of the Trp residue in close proximity of the protein surface and, in the case of rose bengal, to the coincidence of the photophysical properties (including the quantum yield of O 2 ( 1 Δ g ) generation) for the free and HSA‐bound dye. Hematoporphyrin also binds to HSA with 1: 1 stoichiometry, although at a different site from rose bengal. Bound Hp again displays photophysical properties very similar with those of free Hp; however, the efficiency of Trp photo‐oxidation in HSA is about 5‐fold higher than in NATA owing to a limited rearrangement of the protein structure, induced by Hp binding, which enhances the probability of chemical quenching of O 2 ( 1 Δ g ) by the indole ring.