EFFECT OF NUCLEOTIDE SEQUENCE ON THE BINDING OF (–)–ANTI–DIBENZO– [a,l]PYRENE–11,12–DIOL 13,14–EPOXIDE TO SHORT OLIGODEOXYRIBONUCLEOTIDES

Abstract

Seven selfcomplementary decamer oligodeoxyribonucleotides were reacted with (–)–anti–(11R,12S)–dihydrodiol (13S,14R)–epoxide of dibenzo[a,l]pyrene (DB[a,l]PDE). The oligodeoxyribonucleotides were postlabeled with ³³P–ATP, digested to mononucleotides and the amount of adducts formed was determined by HPLC. We found that the nucleotide sequence affects the binding of DB[a,l]PDE to DNA. DB[a,l]PDE binds better to GC rich oligodeoxyribonucleotides than to AT rich oligodeoxyribonucleotides. The CGC sequence binds more DB[a,l]PDE than GGC, TGC, GAT or AGC sequences. The reactions were carried out on ice or at 37°C. There was no evidence of temperature effects on the amount of DB[a,l]PDE binding.     

H2AX,MDM2 AND P53 PHOSPHORYLATION ARE DIFFERENTLY AFFECTED BY BAY- AND FJORD-REGION DIOL EPOXIDES DERIVED FROM CARCINOGENIC POLYCYCLIC AROMATIC HYDROCARBONS

The human lung cancer cell line A549 was exposed to diol epoxides (DEs) and the effect on DNA damage signaling proteins was studied. The DEs used were derived from the bay-region PAHs chrysene; CDE and dibenz[a,h]anthracene; DBADE, or the fjord-region PAHs benzo[c]chrysene; B[c]CDE, benzo[g]chrysene; B[g]CDE and benzo[c]phenanthrene; B[c]PhDE. All DEs induced a rapid response on Mdm2, p53 and histone H2AX phosphorylation, where Mdm2 was the most sensitive marker of DNA damage. Fjord-region DEs induced a stronger and more persistent effect on the proteins studied than the bay-region DEs. This variance is likely to reflect differences in adduct recognition and handling by nucleotide excision repair. The stimulating effect of DEs on histone H2AX phosphorylation demonstrated that, in addition to DNA strand breaks and UV-induced photoproducts, stable and bulky DNA-adducts also possess this capacity.     

A Male-Predominant Cuticular Hydrocarbon, 7-Methyltricosane, is used as a Contact Pheromone in the Western Flower Thrips Frankliniella occidentalis

In a laboratory bioassay, adult female Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) spent more time near filter paper disks that had been exposed to adult males than near unexposed disks; this effect was not observed on disks exposed to adult females. The response could only partly be explained by the known male-produced aggregation pheromone, neryl (S)-2-methylbutanoate, suggesting the presence of an unknown male-produced compound. In gas chromatography/mass spectrometry analyses, 7-methyltricosane was detected on disks exposed to males, but not on disks exposed to females. Extracts of cuticular lipids also showed relatively large amounts of 7-methyltricosane on males, whereas only trace amounts were found on females and none on larvae. Bioassays of synthetic 7-methyltricosane showed that adults responded only after contact. The response to this compound was clearly different from that to n-tricosane or hexane-only controls. Females that contacted 7-methyltricosane on glass beads stayed in the vicinity and frequently raised the abdomen, a behavior that rejects mating attempts by males. Males stayed in the vicinity and wagged the abdomen sideways, a behavior used in fighting between males. This is the first identification of a contact pheromone in the order Thysanoptera.     

Inactivation of Carcinogenic Diol Epoxides of Dibenzo[ a,l ]pyrene (Dibenzo[ def,p ]chrysene) by Human Alpha Class Glutathione Transferases

Human Alpha class glutathione transferases (hGSTs) have been incubated with the ultimate carcinogenic ( m )- anti - and (+)- syn -diol epoxides (DE) of the nonplanar dibenzo[ a,l ]pyrene (DBP). hGSTA1-1, A2-2, and A3-3 demonstrate activity with both diol epoxides ( R -absolute configuration at the benzylic oxirane carbon) whereas hGSTA4-4 virtually was inactive. (+)- syn -DBPDE was superior as substrate compared to the ( m )- anti enantiomer with hGSTA1-1 as the most efficient enzyme (k cat /K M = 464 mM m 1 s m 1 ) followed by A3-3 and A2-2 (k cat /K M = 190 mM m 1 s m 1 and 30.4 mM m 1 s m 1 , respectively). With ( m )- anti -DBPDE, the k cat /K M values were in general about 10-fold lower. Replacing ( m )- anti -DBPDE with the less complex ( m )- anti -BCDE or the less structurally distorted (+)- anti -BPDE, revealed that GSTA1-1 was 19- and 25-fold less active, respectively. hGSTA1-1 is present in human lung, a primary target tissue for PAH-induced tumors. Considering the great efficiency of this isoform relative to both Pi and Mu-class GSTs toward DBPDE, its presence and extent of expression may play a significant role in protection against this type of highly carcinogenic compounds.     

Benzylic Sulfuric Acid Esters React with Diverse Functional Groups and Often form Secondary Reactive Species

The mutagenicity of some benzylic sulfuric acid esters to Salmonella typhimurium is strongly influenced by monovalent anions and other medium components. The formation of highly mutagenic 1-chloromethylpyrene has been previously demonstrated. In the present study we found that the sulfuric acid esters of a primary benzylic alcohol, 1-sulfooxymethylpyrene, and a secondary benzylic alcohol, 4H-sulfooxycyclopenta[def]phenanthrene, exhibit reactivity towards many functional groups abundant in vivo. We identified various reaction products and determined their rates of formation. Many reaction products were still reactive. Their reactivity and selectivity towards nucleophiles varied over a wide range and was differentfrom those of the parent sulfuric acid esters. Thus the formation of these secondary reactive species may explain many of the observed influences of medium components on the mutagenicity of benzylic sulfuric acid esters in vitro and may also affect their effects in vivo.     

Specificity in Chemical Profiles of Workers,Brood and Mutualistic Fungi in <Emphasis Type="Italic">Atta</Emphasis>, <Emphasis Type="Italic">Acromyrmex,</Emphasis> and <Emphasis Type="Italic">Sericomyrmex</Emphasis> Fungus-growing Ants

Neotropical attine ants live in obligatory symbiosis with a fungus that they grow for food on a substrate of primarily plant material harvested by workers. Nestmate recognition is likely based on chemical cues as in most other social insects, but recent studies have indicated that both the ants and their mutualistic fungi may contribute to the recognition templates. To investigate the within-colony variation in chemical profiles, we extracted and identified compounds from the cuticle of workers, the postpharyngeal gland of workers, ant pupae and larvae, and the fungal symbiont of three species of higher attine ants: Atta colombica, Acromyrmex echinatior, and Sericomyrmex amabilis. The relative proportions of identified compounds were compared and represented 11 classes: n-alkanes, alkenes, branched methylalkanes, branched dimethylalkanes, trimethylalkanes, branched alkenes, aldehydes, alcohols, acetates, acids, and esters. The chemical profiles in all three species are likely to be sufficiently different to allow discrimination at the species and colony level and sufficiently similar within colonies to generate a relatively constant colony-specific chemical gestalt. The relative likelihood of individual compounds being derived from the ants, the ant brood, or the fungal symbiont are discussed. We hypothesize that hydrocarbons are particularly important as recognition cues because they appear to simultaneously allow the assessment of developmental stages and the identification of symbiont, colony, and species.     

Dark current measurements on a superconducting cavity using a cryogenic current comparator

This paper presents nondestructive dark current measurements of tera electron volt energy superconducting linear accelerator cavities. The measurements were carried out in an extremely noisy accelerator environment using a low temperature dc superconducting quantum interference device based cryogenic current comparator. The overall current sensitivity under these rough conditions was measured to be 0.2 nA/Hz(1/2), which enables the detection of dark currents of 5 nA.     

Influence of Soluble Polymer Residues in Crosslinked Carboxymethyl Starch on some Physical Properties of its Hydrogels

Crosslinked carboxymethyl starch (CMS) was synthesized from potato starch in a single‐step procedure with mono‐ (MCA) and dichloroacetic acid (DCA), using the well‐known Williamson reaction. The products varied in their degree of substitution DS (average number of carboxymethyl groups per monomer unit) and crosslinker ratio F_z (number of crosslinker molecules offered per monomer unit). After neutralizing and removal of the formed salt, one part of the synthesized CMS networks was pre‐swollen in water in an additional purification step in order to wash out unlinked, soluble polymer chains. The rest of the product remained unwashed. Different swelling experiments were performed with the two samples, before being dried and ground. Both, the Free Swelling Capacity (FSC) and the Absorption Capacity Under Mechanical Load (AUL) of the hydrogels were strongly influenced by chemically unlinked CMS chains that were only physically entangled in the network structure. These mobile polymer segments were responsible for a significant weight loss of the swollen, unwashed hydrogels over the course of time. Rheological oscillatory experiments showed that, in order to achieve comparable values for the storage and loss moduli (G′ and G′′), the polymer content of an unwashed hydrogel had to be more than twice as high as that of the corresponding purified product. By using a special rheological test procedure with a cyclic temperature program, the long‐term stability of CMS gels could be measured and verified.     

Synthese und mesomorphe Eigenschaften von 4-[trans-4-n- Alkylcyclohexanoyloxy]-benzoesäurephenyl- und 4-Benzoyloxybenzoesäure-cyclohexylestern

Synthesis and Mesomorphic Properties of Phenyl 4-[trans-4-n-alkyl-cyclohexanoyloxy]-benzoates and Cyclohexyl-4-benzoyloxybenzoates Synthesis and liquid-crystalline properties of terminal and lateral substituted phenyl 4-[trans-4-n-alkylcyclohexanoyl-oxy]-benzoates 1–13 , cyclohexyl 4-benzoyloxybenzoates 14–17 and phenyl 4-benzoyloxybenzoates 18–23 are described. The effects of alicyclic part and of lateral substituents are discussed.