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At least 19 recordsLinked to original sources
PubMed1977

Control of extraction of deoxyribonucleic acid and apurinic acid by polyethylene glycol in Feulgen hydrolysis.

The polymer polyethylene glycol combined with hydrochloric acid was used during the hydrolysis stage of the Feulgen method in order to limit the movement of the soluble molecular fragments developed through hydrolytic breakdown of the deoxyribonucleic acid. The diffusion of the purines was not influenced by the addition of concentration of the polymer up to 30%. On the other hand, a substantial retardation of the extraction of deoxyribonucleic acid and apurinic acid was noted. This indicates that deoxyribonucleic acid and apurinic acid are extracted in chains of considerable length. The decrease in diffusion rate was greater at 1 M HCl than at 0.3 and 6 M HCl, which indicates that the deoxyribonucleic acid-apurinic acid fragments are larger at the medium concentration of acid than at the low and high concentrations. The results thus strengthen the view that deoxyribonucleic acid and apurinic acid are extracted in chains during hydrolysis, and that the critical length at which the chains becomes diffusible is one of the main factors determining the form of the Feulgen hydrolysis curve. The use of polyethylene glycol to extend the maximum of the hydrolysis curve, and thus to make the temperature and time of hydrolysis less critical, is recommended.

Apurinic Acid↗
PubMed1974

Proton magnetic resonance studies of ultraviolet-irradiated apurinic acid.

In apurinic acid, a single-stranded polydeoxyribonucleotide easily obtained upon depurination of DNA, the proton resonances arising from thymine and cytosine are readily observable in aqueous solution of 25 degrees C. Two methyl thymine resonances, centered at 1.88 ppm and separated by 0.045 ppm, are observed. We attribute the downfield methyl resonance to thymines with no pyrimidine nearest neighbors and the upfield methyl resonance to thymines having pyrimidine neighbors in the 3' and/or 5' positions. Upon ultraviolet irradiation, the upfield methyl and thymine H-6 resonances decrease in amplitude and two methyl resoances appear at 1.63 and 1.52 ppm, corresponding, respectively, to cytosine-thymine and thymine-thymine cyclobutane dimers. Photoreversal eliminates these two minor methyl resonances from the pmr spectrum. We conclude that apurinic acid provides a suitable model system for pmr studies of chemically modified pyrimidine bases in DNA.

Apurinic Acid↗
PubMed1979

Anisotropic staining of apurinic acid with toluidine blue.

Using normal rat liver imprints, studies were carried out on the effects of histone extraction and the formation of aldehyde groups from deoxyribose on anisotropic toluidine blue staining of depurinized DNA after sodium bisulfite treatment. The anisotropic effect of bisulfite was found to be determined by binding of bisulfite ions to the aldehyde groups of apurinic acid which, together with free phosphate groups of DNA ensure coparallel attachment of the dye molecules. It was also shown that at pH 5.0 toluidine blue binds with both the phosphate and aldehyde groups of apurinic acid, to give anisotropic staining.

Animals↗
PubMed1976

Endonuclease II, apurinic acid endonuclease, and exonuclease III.

An endonuclease of Escherichia coli active on a DNA treated with methylmethane sulfonate has been separated from an endonuclease active on depurinated sites. The former enzyme is disignated here as endonuclease II, while the latter enzyme is designated as apurinic acid endonuclease. Endonuclease II is also active on DNA treated with methylnitrosourea, 7-bromomethyl-12-methylbenz[a]anthracene, and gamma-irradiation. A third fraction which contains activities for both depurinated and alkylated sites needs further study. Endonuclease II, molecular weight 33,000, has been purified 12,500-fold and does not have exonuclease III activity. Apurinic acid endonuclease, molecular weight 31,500, has been purified 11,000-fold and does not have exonuclease III activity. Exonuclease III, molecular weight 26,000, has been purified 2300-fold and does not have endonucleolytic activity at depurinated reduced sites or at alkylated sites in DNA. Therefore, these are three separate proteins. Exonuclease III can produce, presumably by its exonucleolytic activity, double-strand breaks in heavily alkylated DNA under conditions where it does not make single-strand endonucleolytic breaks at either depurinated-reduced or alkylated sites.

Alkylation↗
PubMed1988

Dual biological activity of apurinic acid on human lymphocytes: induction of interferon-gamma and protection from human immunodeficiency virus infection in vitro.

The chemically modified DNA, apurinic acid (APA), is cytotoxic for human lymphocytes at concentrations above 100 micrograms/ml. At low concentrations (0.05-1 micrograms/ml) APA acts as an inducer interferon gamma (IFN-gamma) in lymphocytes in vitro; the maximum interferon titer of 50 units/ml was reached at 0.4 micrograms/ml. When added to the cells in combination with phytohemagglutinin A (PHA), APA displays a significant synergistic interferon-inducing ability; the maximum titer of 940 units/ml was obtained with 10 micrograms/ml of APA and 6.25 micrograms/ml of PHA. APA also proved to be an effective inhibitor of human immunodeficiency virus (HIV-1) replication in H9 cells. At a concentration of 10 micrograms/ml, APA causes a 49% inhibition of virus growth, while 20 micrograms/ml of APA are required to inhibit expression of HIV-1 p17 and p24 gag proteins by 60%. The mechanism of anti HIV-1 activity of APA likely occurs at the level of viral reverse transcriptase. This enzyme is inhibited by APA in a noncompetitive way with a Ki of 0.39 microM, while the cellular DNA polymerases alpha, beta and gamma are 140- to 300-fold less sensitive to APA.

Apurinic Acid↗
PubMed1975

The interaction of apurinic acid aldehyde groups with pararosaniline in the Feulgen-Schiff and related staining procedures.

The equilibrium reactions involved in the formation of the apurinic acid (APA)-Schiff chromophores in the staining phase of the Feulgen-Schiff reaction do not allow a quantitative conversion of APA to these chromophores. By modification of the sulfite and dye concentrations and the pH of the staining reagents, or by using better solvents for pararosaniline like acetic acid or dimethylsulfoxide (DMSO) a shift of these equilibria was attempted in order to obtain a higher amount of APA-bound dye. A 40% higher absorbance, when compared with the normal Schiff-staining, was obtained in model films by staining with a saturated solution of pararosaniline in a 1:1 v/v mixture of DMSO and SO2-water, followed by rinsing in SO2-water. A doubling of the absorbance resulted in the same objects when a saturated solution of pararosaniline in a 2 M acetic acid/acetate buffer of pH 4.45 was used for staining, followed by a short rinse in SO2-water. Amino groups (as found in histones) are shown to compete with the amino groups of pararosaniline for the APA aldehydes. This effect, although causing lower staining intensities, is shown not to be the explanation for the differences in stain content found between more and less compact forms of chromatin. Depending on the pH, and dye and sulfite concentrations of the staining reagents, the following components are considered as possible contributors to the mixture of chromophores (Duijndam et al., 1973 b) formed between APA and Schiff's reagent or its modifications: 1. An acid labile component with a wavelength of maximal absorbance (lambda max) near 510 nm; its structure is probably the azomethine--CH=N--; 2. A relatively acid stable component with a high value of molecular absorbance (epsilon), an lambda max near 570 nm and possibly having an enamine structure--CH=CH--NH--; 3. A component with intermediate acid stability, low epsilon, and lambda max near 540 nm, and which is probably an alkylsulfonic acid --CH(SO3H)--NH--compound. Small differences in the staining conditions in the histochemical application of the Feulgen-Schiff reaction may cause a shift in the ratio between especially components 2 and 3, resulting in variations in stain content and in lambda max.

Acetates↗