Stepwise Two-Photon Excitation of 1,5-Dihydroflavin Mononucleotide: Study of Flavosemiquinone Properties

Autor:	Lars Lindqvist, Chaibia El Hanine-Lmoumene
Rok vydání:	1997
Předmět:	Absorbance Microsecond Chemistry Radical Yield (chemistry) Photodissociation General Medicine Flavin group Photoionization Physical and Theoretical Chemistry Photochemistry Biochemistry Excitation
Zdroj:	Photochemistry and Photobiology. 66:591-595
ISSN:	1751-1097 0031-8655
DOI:	10.1111/j.1751-1097.1997.tb03194.x
Popis:	— Photoionization of 1,5-dihydroflavin mononucleotide in aqueous solution, leading to formation of hydrated electrons and flavosemiquinone radicals, was studied by nanosecond laser photolysis (excitation at LD = 354.7 nm). Analysis of the laser fluence dependence of the photoionization yield indicates that the reaction is a stepwise two-photon reaction with the fluorescent state of the flavin as intermediate step. Extinction coefficients of the neutral and anionic flavosemiquinone were obtained from transient absorbance measurements at 310-660 nm. The pro-tolytic dissociation constant of the neutral radical was determined from a study at pH 7.3-10.3 of the spectral evolution in the submicrosecond time range due to de-protonation of this radical. The value pKa= 8.7 0.1 was obtained. The formation of tautomeric species of the neutral flavosemiquinone was suggested based on the existence of a spectral evolution of this species during the first microseconds after excitation.
Databáze:	OpenAIRE
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