Версия от 05:55, 8 марта 2024; EducationBot(обсуждение | вклад)(Новая страница: «{{Английская Википедия/Панель перехода}} {{Short description|Group of chemical compounds}} {{Lead rewrite|date=September 2022|reason=Per MOS:INTRO, "avoid difficult-to-understand terminology" in the lead.}}alt=|thumb|There are 18 key atoms in [[isoalloxazine that make up its characteristic three-ring structure. The R-group varies and differentiates various flavins.]] Image:Riboflavin.svg|thumb|...»)
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In aqueous solution, flavins are yellow-coloured when oxidized, taking a red colour in the semi-reduced anionic state or blue in the neutral (semiquinone) state, and colourless when totally reduced.[1] The oxidized and reduced forms are in fast equilibrium with the semiquinone (radical) form, shifted against the formation of the radical:[2]
Flox + FlredH2 ⇌ FlH•
where Flox is the oxidized flavin, FlredH2 the reduced flavin (upon addition of two hydrogen atoms) and FlH• the semiquinone form (addition of one hydrogen atom).
In the form of FADH2, it is one of the cofactors that can transfer electrons to the electron transfer chain.
Both free and protein-bound flavins are photoreducible, that is, able to be reduced by light, in a mechanism mediated by several organic compounds, such as some amino acids, carboxylic acids and amines.[2] This property of flavins is exploited by various light-sensitive proteins. For example, the LOV domain, found in many species of plant, fungi and bacteria, undergoes a reversible, light-dependent structural change which involves the formation of a bond between a cysteine residue in its peptide sequence and a bound FMN.[3]
