Formaldehyde reaction with nucleic acids

Figure 3.1 Two essential steps of chemical reaction of formaldehyde (HCHO) with nucleic acid exemplified by adenine that are similar to formaldehyde-protein reactions, (a) Addition reaction as the first step, resulting in a methylol derivative, methylol adenylic acid (b) Second step is a condensation reaction, a stable product methylene-bis-adenylic acid is derived between the methylol derivative and another adenine. Reproduced with permission from Shi et al.,AIMM 2001 9 107-116. 

N-AryInitrones (XIII) formed by oxidation of N-hydroxy-N-methyl arylamines, show high reactivity toward carbon-carbon and carbon-nitrogen double bonds in non-aqueous media (21,203) (Figure 10). Under physiological conditions, however, it appears that N-arylnitrones exist as protonated salts that readily hydrolyze to formaldehyde and a primary N-hydroxy arylamine and efforts to detect N-arylnitrone addition products in cellular lipid, protein or nucleic acids have not been successful (204). Nitroxide radicals derived from N-hydroxy-MAB have also been suggested as reactive intermediates (150), but their direct covalent reaction with nucleic acids has been excluded (21). 

Casanova. M.. Bell. D.A. Heck, H. (1997) Dichloromethane metabolism to formaldehyde and reaction of formaldehyde with nucleic acids in hepatocytes of rodents and humans with and without glutathione S-transferase Tl wAMl genes. Fundam. appl. Toxicol, 31, 168— 180... 

Feldman MY. 1976. Reactions of nucleic acids and nucleoproteins with formaldehyde. Prog Nucleic Acid Res Mol Biol 13 1-49. 

In general, the mechanism of heat and alkaline solution for DNA extraction may be based upon a hypothesis, previously proposed for the AR technique.32 Strong alkaline solution may denature and hydrolyze proteins, resulting in breaking cell and nuclear membranes as well as disrupting cross-linkages due to formalin fixation. It is no surprise to observe the similarity between retrieval of nucleic acid and retrieval of protein (antigen) based on a similar chemical reaction of formaldehyde with these two kinds of macromolecules (Fig. 3.1).15"19... 

Metabolically, formaldehyde is rapidly oxidized to formic acid (see Section 14.7), which is responsible in large part for its toxicity. Formaldehyde reacts by addition and condensation reactions with a variety of biocompounds, including DNA and proteins, and in so doing forms adducts and DNA-protein cross-links.9 Formaldehyde is incorporated into proteins and nucleic acids as the -CH3 group. Reactive formaldehyde has a short systemic lifetime of only about 1 min its formic acid metabolic product has a longer metabolic lifetime. 

The activity of EtO, similar to many other disinfectants, preservative, and sterilizing agents, such as formaldehyde, beta-propiolactone, methylbromide, and ethylenimine, depends on an alkylation reaction. This reaction occurs with some groups within the complex enzymes, proteins, and nucleic acids in the bacterial cell. These compounds can then no longer be effective or necessary to the vital processes of the microorganism cell. Furthermore, one would expect these effects to vary according to the extensions of reactions static, mutagenic, or toxic. 

Nondiamine chemical reduction stains use silver nitrate to provide silver ions for reaction with protein and nucleic acid sites under acidic conditions (Merril, 1986, 1990). Image development is initiated by placing the gel in an alkaline solution, using sodium carbonate and/or hydroxide or other bases to maintain the alkaline pH, while the silver ions are selectively reduced to metallic silver with formaldehyde. The formic acid, produced by the oxidation of formaldehyde, is buffered by the sodium carbonate. This type of stain is relatively rapid and simple to perform. The nondiamine stains generally work best with gels 1 mm or less in thickness. 

FIGURE 1.8 Some chemical reactions of bases and nucleotides, (a) Hydrolysis of a dinucleotide by alkali. Bases are denoted by B1 and B2. R denotes ribose or deoxyribose. (b to k) Chemical reactions (b) bisulfite, (c) chloroacetaldehyde, (d) diethyl pyrocarbonate, (e) dimethyl sulfate, (f) formaldehyde, (g) glyoxal, (h) hydrazine, (i) nitric acid, (j) nitrous acid, and (k) osmium tetroxide. Partly from R. L. P. Adams, J. P. Knowler, and D. P. Leader (1986). In The Biochemistry of the Nucleic Acids, 10th ed., pp. 5—34. Chapman Hall, with permission. 

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