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Medium Design for Cell Culture Processing
Published in Wei-Shou Hu, Cell Culture Bioprocess Engineering, 2020
Niacin, or nicotinamide (vitamin B3), is a precursor of NAD and NADP. Riboflavin (vitamin B2) or flavin mononucleotide (FMN) and flavin adenosine dinucleotide (FAD) are important cofactors in many bio-chemical reactions.
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.
Polarised fluorescence in FAD excited at 355 and 450 nm in water–propylene glycol solutions
Published in Molecular Physics, 2022
D. M. Beltukova, M. K. Danilova, I. A. Gradusov, V. P. Belik, I. V. Semenova, O. S. Vasyutinskii
Optical properties of FAD have been the subject of intensive studies for decades. In his pioneering paper, more than 70 years ago Weber [7] observed the remarkably low fluorescence of FAD with respect to flavin mononucleotide (FMN) and riboflavin (RF) and associated this effect with the formation of a long-living non-fluorescing complex between the Iso and Ad moieties. Most of the authors concluded that FAD in aqueous solution can exist in two conformations: a ‘stack' conformation, where the Iso and Ad moieties are in close proximity with each other that provides electron transfer reactions resulting in fast (picosecond) radiationless deactivation of excited states, and an ‘open’ conformation, where the two moieties are separated from each other [8–11]. The stack conformation is stabilised by a interaction between the Iso and Ad aromatic rings. Only the unfolded conformation can fluoresce, while the stack conformation cannot. In aqueous solution, FAD is considered to predominantly exist in the stack conformation, while an addition of less polar solvents prevents the interaction and produces the open conformation resulting in the increase of the fluorescence quantum yield [11–15]. Molecular dynamic simulations performed for FAD in free and enzyme-bound states demonstrated that FAD may adopt intermediate conformations rather than just the ‘stack’ or ‘open’ ones [16]. The existence of intermediate partially ‘stack’ conformations of FAD was also revealed by Li et al. using aerolysin nanopores [17].
Functional sustainability of nutrient accumulation by periphytic biofilm under temperature fluctuations
Published in Environmental Technology, 2021
Rui Sun, Ying Xu, Yonghong Wu, Jun Tang, Sofia Esquivel-Elizondo, Philip G. Kerr, Philip L. Staddon, Junzhuo Liu
Dehydrogenase is a kind of oxidoreductases and it oxidizes a substrate by reducing an electron acceptor, usually nicotinamide adenine dinucleotide (NAD+)/ nicotinamide adenine dinucleotide phosphate (NADP+), flavin adenine dinucleotide (FAD) or flavin mononucleotide (FMN), and dehydrogenase activity directly correlates with the organic matter degradation capacity of the periphytic biofilm [34,35]. We determined the dehydrogenase activity of the periphytic biofilms in the different temperature phases with results revealing a similar pattern to the utilization of different substrates with temperature variation (Figure 1(d)). Although the temperature increase stimulated the periphytic biofilm carbon metabolic and dehydrogenase activities, the carbon metabolic activity and dehydrogenase activity of the periphytic biofilm reverted to the original level when the temperature fell back to the initial range (17°C).
Transgenic tobacco plants overexpressing a cold-adaptive nitroreductase gene exhibited enhanced 2,4-dinitrotoluene detoxification rate at low temperature
Published in International Journal of Phytoremediation, 2021
Doğa Selin Kayıhan, Ceyhun Kayıhan, Yelda Özden Çiftçi
A newly characterized nitroreductase gene (Ntr) from uropathogenic Staphylococcus saprophyticus showed its optimal activity at 20 °C and maintained its major activity between 3-40 °C (Çelik and Yetiş 2012). It is flavin mononucleotide containing flavoenzyme and uses reducing power of either nicotinamide adenine dinucleotide (NADH) or nicotinamide adenine dinucleotide phosphate (NADPH). Catalyzation of two electron reduction of a nitroaromatic antibiotic (nitrofurazone) and some cancer prodrugs (CB1954 and SN23862) by Ntr was exhibited (Çelik and Yetiş 2012). Importantly, the highest transformation capacity of Ntr was previously determined for 2,4-DNT from several nitrotoluens (data not shown). Hence, in this study, our aim was to obtain transgenic tobacco (Nicotiana tabacum) plants overexpressing Ntr which were able to detoxify 2,4-DNT especially at low temperature. After we had confirmed the existence of heterologous expression in transgenic plants, we investigated physiological and stress related parameters in plants exposed to 2,4-DNT toxicity under normal (22 °C), mild-low (15 °C) and low temperatures (4 °C). Moreover, we determined 2,4-DNT uptake level of the transgenic and wild-type (WT) plants under these conditions.