Polyaromatic Moieties Research Articles

Incorporation of 3-Aminobenzanthrone into 2′-Deoxyoligonucleotides and Its Impact on Duplex Stability

3-Nitrobenzanthrone (3NBA), an environmental pollutant and potent mutagen, causes DNA damage via the reaction of its metabolically activated form with the exocyclic amino groups of purines and the C-8 position of guanine. The present work describes a synthetic approach to the preparation of oligomeric 2′-deoxyribonucleotides containing a 2-(2′-deoxyguanosin-N2-yl)-3-aminobenzanthrone moiety, one of the major DNA adducts found in tissues of living organisms exposed to 3NBA. The NMR spectra indicate that the damaged oligodeoxyribonucleotide is capable of forming a regular double helical structure with the polyaromatic moiety assuming a single conformation at room temperature; the spectra suggest that the 3ABA moiety resides in the duplex minor groove pointing toward the 5′-end of the modified strand. Thermodynamic studies show that the dG(N2)-3ABA lesion has a stabilizing effect on the damaged duplex, a fact that correlates well with the long persistence of this damage in living organisms.

KO2 chemical transformation/mass spectrometry detection of covalent damage to the DNA of cultured human lymphocytes exposed to benzo[a]pyrene.

Cultured human lymphocytes were exposed to benzo[a]pyrene (B[a]P), and diol epoxide-type DNA adducts arising from this chemical were detected by a method consisting of the following sequence of steps: (1) isolate the DNA; (2) subject the DNA to mild acid hydrolysis to release the polyaromatic moiety as a tetrahydrotetrol; (3) add an internal standard; (4) oxidize the tetrahydrotetrol with potassium superoxide to pyrene-2,3-dicarboxylic acid; (5) derivatize the latter with pentafluorobenzyl bromide; (6) purify the diester product on a silica cartridge; and (7) detect this product by gas chromatography electron capture negative ion mass spectrometry. From the dose (1 microgram/mL) of B[a]P applied, five adducts in 10(7) normal nucleotides were found. Largely because steps 2-5 of the method take place sequentially in a single vial, the procedure is convenient and affords precise results. To demonstrate the potential of the method to detect KO2-susceptible polyaromatic hydrocarbon DNA adducts in general, including unknowns, it was also applied to picomole and femtomole amounts of a standard of chrysene-1,4-quinone using scanning and selected ion monitoring conditions, respectively, in the MS. Since standard products can be detected with selected ion monitoring at levels 10(4) below those encountered here (prior work), it should be possible in the future to extend the method to samples containing smaller amounts of such adducts.

Liquefaction behaviour of coals: a study by field ionization mass spectrometry and pattern recognition

Twenty Polish coals (72–88 wt% C, daf) were reacted with tetralin at 400 °C and the conversions were determined. Field ionization (f.i.) mass spectra in the m z range 100–700 were obtained by in-source volatilization from 50 to 500 °C. Pattern recognition was applied to five replicates of the integrated, normalized f.i. mass spectra, conversion data, and proximate and ultimate analyses of the coals. A number of selected f.i. mass signals and conventional parameters showed high discriminatory power and hence can be used for classification of coals and prediction of conversion. In particular, the intensities of 45 f.i. mass signals were found to be significantly correlated with conversion for the coals investigated. The specific features of soft ionization mass spectrometry mean that almost exclusively molecular ions of low-temperature thermal degradation products are generated. It is therefore concluded that the correlated mass signals contain relevant information about reactive sites of the coal organic matter that are involved in liquefaction. The preliminary results indicate that some CO and CC bonds as well as polyaromatic moieties are the primary targets in the process of hydrogen transfer.