Adenine, oxidation

Rhaese H -J (1968) Chemical analysis of DNA alterations III. Isolation and characterization of adenine oxidation products obtained from oligo- and monodeoxyadenylic acids treated with hydroxyl... 

However, if a potential of —0.60 V was applied to the DNA biosensor during 120 s, big changes occurred inside the DNA layer (Fig. 20.6). Two new oxidation peaks appeared, which can be identified [2] the first at +0.80 V, as guanine oxidation, and the second at +1.05V, as adenine oxidation. Nevertheless, the oxidation peak potentials for guanosine and adenine are very close, making their identification difficult. 

The discussion in Section 18.5 on simulations of the EPR spectra of DNA mentioned room for improvements. It would be very interesting to add new structures discussed herein to the simulations. New simulations should include sugar radicals, accurate hyperfine couplings from the EPR/ENDOR studies, perhaps an adenine oxidation product, and the oxidation product in 5-MeCytosine. Some of the DNA simulations Huttermann and co-workers performed included the thymine allyl radical [23], This assignment seemed improbable at the time since oxidation of thymine is not expected in DNA. It would be interesting to know if this allyl component used in the simulations might actually be from an oxidized 5-MeCytosine. 

Nicotinic, acid Nicotinarnide adenine Oxidation-reduction Pellagra (dermatitis. 

Adenine oxidation peak can also be observed and detected, but it has been chosen to use guanine peak only because it gave more reproducible signals. 

Table IX Hyperfine Coupling Parameters for Adenine Oxidation Products ...

A-tetrad 188 absorption 62 AcesII program 142 acid-base pairs 152 adenine 162, 186 adenine oxidation products 235 adenine reduction products 233 alanine 24... 

Figure 13.4. Label-free voltammetric hybridization detection based on guanine adenine oxidation.

FIGURE 15 5 Structure of NAD the oxidized form of the coenzyme nicotinamide adenine dinucleotide The functional part of the coen zyme is framed in red... 

Section 15 11 Oxidation of alcohols to aldehydes and ketones is a common biological reaction Most require a coenzyme such as the oxidized form of nicotin amide adenine dmucleotide (NAD" )... 

Figure 11.39 summarizes the reactions taking place in this amperometric sensor. FAD is the oxidized form of flavin adenine nucleotide (the active site of the enzyme glucose oxidase), and FAD1T2 is the active site s reduced form. Note that O2 serves as a mediator, carrying electrons to the electrode. Other mediators, such as Fe(CN)6 , can be used in place of O2. 

Insects poisoned with rotenone exhibit a steady decline ia oxygen consumption and the iasecticide has been shown to have a specific action ia interfering with the electron transport iavolved ia the oxidation of reduced nicotinamide adenine dinucleotide (NADH) to nicotinamide adenine dinucleotide (NAD) by cytochrome b. Poisoning, therefore, inhibits the mitochondrial oxidation of Krebs-cycle iatermediates which is catalysed by NAD. 

Glucose [50-99-7] urea [57-13-6] (qv), and cholesterol [57-88-5] (see Steroids) are the substrates most frequentiy measured, although there are many more substrates or metaboUtes that are determined in clinical laboratories using enzymes. Co-enzymes such as adenosine triphosphate [56-65-5] (ATP) and nicotinamide adenine dinucleotide [53-84-9] in its oxidized (NAD" ) or reduced (NADH) [58-68-4] form can be considered substrates. Enzymatic analysis is covered in detail elsewhere (9). 

Indicators There are certain compounds that are suitable as indicators for sensitive and specific clinical analysis. Nicotinamide adenine dinucleotide (NAD) occurs in oxidized (NAD" ) and reduced (NADH) forms. Nicotinamide adenine dinucleotide phosphate (NADP) also has two states, NADP" and NADPH. NADH has a very high uv—vis absorption at 339 nm, extinction coefficient = 6300 (M cm) , but NAD" does not. Similarly, NADPH absorbs light very strongly whereas NADP" does not. 

Adenine, 3-methyl-9- -D-ribofuranosyl-synthesis, 5, 586 Adenine, 2-methylthio-oxidation, 5, 561 Adenine, 2-phenyl-synthesis, 5, 569 Adenine, 2- -pyridyl-synthesis, 5, 569 Adenine, 8-ribofuranosyl-synthesis, 5, 585 Adenine, 3- -D-ribofuranosyl-synthesis, 5, 595... 

Adenine, 9- -D-ribofuranosyl-, 5, 536 Adenine, 8-ribosyl-synthesis, 5, 585 Adenine, 2-thio-dethiation, 5, 558 1-oxide... 

In oiological systems, the most frequent mechanism of oxidation is the remov of hydrogen, and conversely, the addition of hydrogen is the common method of reduc tion. Nicotinamide-adenine dinucleotide (NAD) and nicotinamide-adenine dinucleotide phosphate (NADP) are two coenzymes that assist in oxidation and reduction. These cofactors can shuttle between biochemical reac tions so that one drives another, or their oxidation can be coupled to the formation of ATP. However, stepwise release or consumption of energy requires driving forces and losses at each step such that overall efficiency suffers. 

Oxidation of P-nicotinamide adenine dinucleotide (NADH) to NAD+ has attracted much interest from the viewpoint of its role in biosensors reactions. It has been reported that several quinone derivatives and polymerized redox dyes, such as phenoxazine and phenothiazine derivatives, possess catalytic activities for the oxidation of NADH and have been used for dehydrogenase biosensors development [1, 2]. Flavins (contain in chemical structure isoalloxazine ring) are the prosthetic groups responsible for NAD+/NADH conversion in the active sites of some dehydrogenase enzymes. Upon the electropolymerization of flavin derivatives, the effective catalysts of NAD+/NADH regeneration, which mimic the NADH-dehydrogenase activity, would be synthesized [3]. 

Adenine (6-amino purine) and guanine (2-amino-6-oxy purine), the two common purines, are found in both DNA and RNA (Figure 11.4). Other naturally occurring purine derivatives include hypoxanthlne, xanthine, and uric acid (Figure 11.5). Flypoxanthine and xanthine are found only rarely as constituents of nucleic acids. Uric acid, the most oxidized state for a purine derivative, is never found in nucleic acids. 

Nicotinamide is an essential part of two important coenzymes nicotinamide adenine dinucleotide (NAD ) and nicotinamide adenine dinucleotide phosphate (NADP ) (Figure 18.19). The reduced forms of these coenzymes are NADH and NADPH. The nieotinamide eoenzymes (also known as pyridine nucleotides) are electron carriers. They play vital roles in a variety of enzyme-catalyzed oxidation-reduction reactions. (NAD is an electron acceptor in oxidative (catabolic) pathways and NADPH is an electron donor in reductive (biosynthetic) pathways.) These reactions involve direct transfer of hydride anion either to NAD(P) or from NAD(P)H. The enzymes that facilitate such... 

A-Chlorosuccinimide 1 N NaOH." With this method, the sulfide is oxidized completely to the sulfone, which is cleaved with hydroxide more readily than the sulfoxide formed by periodate oxidation. It has been reported that oxidation of the sulfide leads to oxidation of adenine and gua-nine." However, see the discussion of the TPTE group below. 

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