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ROOM‐TEMPERATURE PHOSPHORESCENCE FROM AZURIN DERIVATIVES. PHOSPHORESCENCE QUENCHING IN OXIDIZED NATIVE AZURIN
Author(s) -
Klemens Frank K.,
McMillin David R.
Publication year - 1992
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.1751-1097.1992.tb08509.x
Subject(s) - azurin , phosphorescence , quenching (fluorescence) , chemistry , photochemistry , electron transfer , tryptophan , fluorescence , biochemistry , physics , amino acid , quantum mechanics
— The tryptophan phosphorescence from a series of derivatives of Pseudomonas aeruginosa azurin has been monitored at 30°C in pH 8.5 buffer solution. The phosphorescence lifetimes fall in the range of 230–270 ms for deoxygenated solutions of derivatives containing Cd(II), Cu(I), Co(II), Ni(II), Hg(II) or apoazurin. A weak signal with a lifetime of ca 130 ms is observed from solutions of oxidized native azurin, but this component is ascribed to a modified form of azurin in solution, i.e. protein heterogeneity, on the basis of the unique sensitivity to quenching by dioxygen. Aside from this minor component, the tryptophan phosphorescence in the Cu(II) protein appears to be fully quenched. The quenching is assigned an electron‐transfer mechanism involving transient reduction of the metal center. The same mechanism is deemed to be responsible for fluorescence quenching in oxidized native azurin as well. These observations are of interest because aromatic groups like tryptophan may be conduits for physiological electron‐transfer processes involving the copper center.