Flavin-adenine dinucleotide formula

FIGURE 10.1 The structural formula of riboflavin and partial structures of riboflavin compounds. The latter show only those portions of the molecule that differ from riboflavin. 1 — Riboflavin (RF), 2 — flavin mononucleotide or 5 -riboflavin monophosphate (FMN or 5 -FMN), 3 — flavin adenine dinucleotide (FAD). 

Rgure 2 Structural formulae of two enzyme cofactors (A) nicotinamide adenine dinucleotide (NAD) and (B) flavin adenine dinucleotide (FAD) with the corresponding redox transformations in dehydrogenases and oxidases catalyzed reaction, respectively. NAD is a soluble cofactor and it has to be added to the reaction mixture. As shown in Figure 1, FAD is bound to the flavoprotein. 

Other popular sensitisers of singlet oxygen formation are acridin orange, methylene blue, and tolui-din blue (formula [79]) but many biological compounds are also effective in vitro, such as the water-soluble vitamin riboflavin and its derivatives flavin mononucleotide and flavin adenine dinucleotide. 

Figure 1 Structural formulae of riboflavin, FMN, and FAD (1) riboflavin in oxidized (FL j) or reduced form (FL, ) (2) FMN, flavin mononucleotide (3) FAD, flavin adenine dinucleotide. ...

Most flavoproteins, however, do not contain the mononucleotide, but rather flavin-adenine dinucleotide, abbreviated FAD. As in the pyridine nucleotides, adenosine monophosphate and riboflavin phosphate are joined by a pyrophosphate bond. The formula is shown below. 

An important aspect of enzymatic oxidation-reduction reactions involves the transfer of hydrogen atoms. This transfer is mediated by coenzymes (substances that act together with enzymes) nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). These two species pick up H atoms to produce NADH and NADPH, respectively, both of which can function as hydrogen atom donors. Another pair of species involved in oxidation-reduction processes by hydrogen atom transfer consists of flavin adenine triphosphate (FAD) and its hydrogenated form FADH2. The structural formulas of NAD and its cationic form, NAD+, are shown in Figure 4.7. 

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