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Hydrogen Atoms Are Produced When Tryptophan within a Protein Is Irradiated with Ultraviolet Light
Author(s) -
Angiolillo Paul J.,
Vanderkooi Jane M.
Publication year - 1996
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.1751-1097.1996.tb03095.x
Subject(s) - electron paramagnetic resonance , chemistry , hyperfine structure , photodissociation , tryptophan , photochemistry , spectroscopy , solvent , spectral line , ultraviolet , crystallography , amino acid , nuclear magnetic resonance , organic chemistry , materials science , atomic physics , biochemistry , physics , optoelectronics , quantum mechanics , astronomy
— The UV photolysis of the aromatic amino acid, tryptophan (Trp), in the Ca 2+ ‐binding protein, cod paralbumin, type III, was studied using electron paramagnetic resonance (EPR) spectroscopy in the temperature range 4–80 K. For the Ca 2+ ‐bound protein, irradiation with UV light (250–400 nm) resulted in the generation of atomic hydrogen with a hyperfine splitting of 50.9 mT, whereas in the Ca 2+ ‐free form, where the Trp is exposed to solvent, the trapped atomic hydrogen was not in evidence. In the same spectra, the radical signal in the g = 2.00 region could be detected. The line shape of the Ca 2+ ‐bound form is similar to the EPR line shape obtained for Trp in micellar systems. In contrast, the EPR line shape for the Ca 2+ ‐free form is essentially featureless up to 80 K. The EPR spectra of the photoproducts of Trp and the nature of the photoreactions are therefore sensitive to the environment of Trp within the protein.