Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5375692 | Chemical Physics | 2008 | 13 Pages |
Abstract
The absorption and fluorescence behaviour of the circadian blue-light photoreceptor cryptochrome from Drosophila melanogaster (dCry) in a pH 8 aqueous buffer solution is studied. The flavin adenine dinucleotide (FAD) cofactor of dCry is identified to be present in its oxidized form (FADox), and the 5,10-methenyltetrahydrofolate (MTHF) cofactor is found to be hydrolyzed and oxidized to 10-formyldihydrofolate (10-FDHF). The absorption and the fluorescence behaviour of dCry is investigated in the dark-adapted (receptor) state, the light-adapted (signalling) state, and under long-time violet light exposure. Photo-excitation of FADox in dCry causes a reductive electron transfer to the formation of anionic FAD semiquinone (FADâ), and photo-excitation of the generated FADâ causes an oxidative electron transfer to the back formation of FADox. In light adapted dCry a photo-induced equilibrium between FADox and FADâ exists. The photo-cycle dynamics of signalling state formation and recovery is discussed. Quantum yields of photo-induced signalling state formation of about 0.2 and of photo-induced back-conversion of about 0.2 are determined. A recovery of FADâ to FADox in the dark with a time constant of 1.6Â min at room temperature is found.
Keywords
Related Topics
Physical Sciences and Engineering
Chemistry
Physical and Theoretical Chemistry
Authors
J. Shirdel, P. Zirak, A. Penzkofer, H. Breitkreuz, E. Wolf,