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Bioremediation of Cr(VI)-Contaminated Soil using Bacteria
Published in Maulin P. Shah, Removal of Refractory Pollutants from Wastewater Treatment Plants, 2021
Flavin mononucleotide (FMN) is a strong, often covalently bound, and is a part of flavoproteins. The oxidized flavin nucleotide [FMN(Ox.)] accepts one semiquinone-producing electron (a stable free radical) to form FMNH(Sq.).
Reaction Kinetics in Food Systems
Published in Dennis R. Heldman, Daryl B. Lund, Cristina M. Sabliov, Handbook of Food Engineering, 2018
Ricardo Villota, James G. Hawkes
Riboflavin, or vitamin B2 (also referred to as vitamin G, lactoflavine, and chemically as 7,8-dimethyl-10-(1′-ribityl) isoalloxazine), is a precursor of the flavin cofactors, FAD (flavin adenine dinucleotide [riboflavin-5′-trihydr ogen-diphosphate]) and FMN (flavin-mononucleotide [riboflavin-5′-monophosphate]), which function in many important enzymatic redox reactions in intermediary metabolism (Figure 3.12). Riboflavin exists in dietary sources predominantly in the form of its coenzyme derivatives, FAD and FMN, which in turn can carry out one- and two-electron transfer reactions involved in diverse biochemical catalytic reactions. Henriques et al. (2010) have presented an overview of many of the updated riboflavin biochemical mechanisms, with particular emphasis on deficiencies of the vitamer and their implications on fatty acid metabolism. The actual free form of riboflavin is more frequently found in commercial multivitamin applications. Common biological sources of B2 are similar to most of the other B-vitamins, including eggs, milk, cheese, meats (liver and kidneys), yeast, and leafy green vegetables. From a nutritional perspective, it should be pointed out that, although green plants can synthesize their own free riboflavin and mammals cannot, the relative amounts found in meat sources (as NAD and FMN) are significantly higher than totals found in most plants. In that FAD and FMN occur chiefly in non-covalently-bound forms to enzymes, while covalently-bound flavins are less available for absorption, are all factors to consider when carrying out vitamer analyses. More detailed reviews of the biochemical function of the flavins have been published (Powers, 2003; Henriques et al.; 2010; Pinto and Rivlin, 2014). Riboflavin is relatively stable in foods under ordinary conditions, as long as it is not exposed to light. It has relatively low water solubility (0.067–0.333 mg/ml) and exhibits a fluorescent yellow-green color (Merck, 2002), which can limit its ability for fortification from a visual perspective, although it may be used as a food colorant with potential health benefits (Table 3.4). FMN has slightly higher solubility and may be a better choice for liquid applications; however, color may still be an issue, as this is also used as a colorant in Europe (E101a). Stability of riboflavin is pH dependent, being more stable under acidic conditions, with maximum stability to heat being between pH 2.0 and 5.0 and destruction of the isoalloxazine ring at pH > 7.0 (Ball et al., 1994). With regard to FAD and FMN, they are both readily converted to riboflavin at pH < 5.0 (Russell and Vanderslice, 1990). This factor is actually used as a prestep when analyzing for total riboflavin; however, it should be avoided if analyzing for each of the three vitamers individually.
On the influence of dimerisation of lumiflavin in aqueous solution on its optical spectra – a quantum chemical study
Published in Molecular Physics, 2019
Daria Brisker-Klaiman, Andreas Dreuw
Flavins serve as co-factors in a variety of proteins and mediate diverse biological functions. They are redox-active, and were, for example, shown to catalyse redox reactions in respiratory enzymes [1]. Flavins are also photo-reactive and flavin-containing proteins act as blue light receptors such as phototropins, cryptochromes and photolyases [2,3]. The importance of flavins in enzymatic function has triggered much attention and their photochemical and photophysical features were therefore extensively studied [1–19].