1088-56-8Relevant articles and documents
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Karrer,Schoepp
, p. 1557 (1934)
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Smith,Metzler
, p. 3285 (1963)
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15N solid-state NMR provides a sensitive probe of oxidized flavin reactive sites
Koder Jr., Ronald L.,Walsh, Joseph D.,Pometun, Maxim S.,Dutton, P. Leslie,Wittebort, Richard J.,Miller, Anne-Frances
, p. 15200 - 15208 (2006)
Flavins are central to the reactivity of a wide variety of enzymes and electron transport proteins. There is great interest in understanding the basis for the different reactivities displayed by flavins in different protein contexts. We propose solid-state nuclear magnetic resonance (SS-NMR) as a tool for directly observing reactive positions of the flavin ring and thereby obtaining information on their frontier orbitals. We now report the SS-NMR signals of the redox-active nitrogens N1 and N5, as well as that of N3. The chemical shift tensor of N5 is over 720 ppm wide, in accordance with the predictions of theory and our calculations. The signal of N3 can be distinguished on the basis of coupling to 1H absent for N1 and N5, as well as the shift tensor span of only 170 ppm, consistent with N3's lower aromaticity and lack of a nonbonding lone pair. The isotropic shifts and spans of N5 and N1 reflect two opposite extremes of the chemical shift range for "pyridine-type" N's, consistent with their electrophilic and nucleophilic chemical reactivities, respectively. Upon flavin reduction, N5's chemical shift tensor contracts dramatically to a span of less than 110 ppm, and the isotropic chemical shift changes by approximately 300 ppm. Both are consistent with loss of N5's nonbonding lone pair and decreased aromaticity, and illustrate the responsiveness of the 15N chemical shift principal values to electronic structure. Thus. 15N chemical shift principal values promise to be valuable tools for understanding electronic differences that underlie variations in flavin reactivity, as well as the reactivities of other heterocyclic cofactors.
A Remarkable Oxidative Cascade That Replaces the Riboflavin C8 Methyl with an Amino Group during Roseoflavin Biosynthesis
Jhulki, Isita,Chanani, Prem K.,Abdelwahed, Sameh H.,Begley, Tadhg P.
, p. 8324 - 8327 (2016/07/26)
Roseoflavin is a naturally occurring riboflavin analogue with antibiotic properties. It is biosynthesized from riboflavin in a reaction involving replacement of the C8 methyl with a dimethylamino group. Herein we report the identification of a flavin-dependent enzyme that converts flavin mononucleotide (FMN) and glutamate to 8-amino-FMN via the intermediacy of 8-formyl-FMN. A mechanistic proposal for this remarkable transformation is proposed.
Riboflavin degradation in the presence of quercetin in methanol under continuous UV-B irradiation: The ESI-MS-UHPLC analysis
Stanojevi?, Jelena S.,Zvezdanovi?, Jelena B.,Markovi?, Dejan Z.
, p. 1787 - 1794 (2015/10/29)
The presented work deals with continuous UV-B irradiation of riboflavin in MeOH solution, leading to its degradation under anaerobic as well as aerobic conditions (faster in the former case), which is related to riboflavin photosensitizing properties (type I photosensitizer in the first case, and type II in the other one). Addition of quercetin, a well-known antioxidant in the system causes a decrease of the (riboflavin) degradation in both cases. In anaerobic conditions it might be a consequence of quercetin antioxidant scavenging activity, while under aerobic conditions it could be related to singlet oxygen formation. The degradation dynamics - in both systems, in the presence and in the absence of quercetin - is well synchronized with dynamics formation of the two major products, lumiflavin and lumichrome
