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Guanine adduct

There is strong evidence that DNA adduction by these bulky reactive metabolites of PAHs is far from random, and that there are certain hot spots that are preferentially attacked. Differential steric hindrance and the differential operation of DNA repair mechanisms ensure that particular sites on DNA are subject to stable adduct formation (Purchase 1994). DNA repair mechanisms clearly remove many PAH/ guanine adducts very quickly, but studies with P postlabeling have shown that certain adducts can be very persistent—certainly over many weeks. Evidence for this has been produced in studies on fish and Xenopus (an amphibian Reichert et al. 1991 Waters et al. 1994). [Pg.188]

Ford and Thompson used semiempirical methods to evaluate the relative stabilities of various nitrenium ion guanine adducts where the exocyclic 2-amino group of guanine is coupled to nitrogen and various ring positions of phenyl or... [Pg.609]

The diol-epoxide contains a reactive carbon center, namely the C-10 position, which can open to form a carbonium ion that is susceptible to nucleophilic attack (Scheme 3.4). The predominant nucleophile among DNA bases is guanine, which preferentially interacts with the carbonium ion at the N2-amine position of guanine to form the BaP-N 2-guanine adduct. The epoxide bond of the diol-epoxide metabolite is particularly resistant to hydrolysis because it is located in the Bay region of the BaP molecule, where steric hindrance prevents the attack of hydrolytic enzymes, such as epoxide hydrolase. [Pg.61]

The genetic consequence of BaP-N2-guanine adduct formation can be associated with errors in base pairing during DNA replication, for example, base substitutions. [Pg.61]

Tretyakova, N.Y, Sangaiah, R., Yen, T.Y. Swenberg, J.A. (1997c) Synthesis, characterization, and in vitro quantitation of N7-guanine adducts of diepoxy butane. Chem. Res. Toxicol., 10,779-785... [Pg.222]

Figure 8.3 Formation of the bulky guanine adduct of (+)-benzo(a)pyrene-7,8-diol-9,10-epoxide-2. Figure 8.3 Formation of the bulky guanine adduct of (+)-benzo(a)pyrene-7,8-diol-9,10-epoxide-2.
The N7-guanine adduct (22) is a urinary excretion product derived from the reaction of sulfur mustard with DNA. It can be isolated from urine by SPE on C18. GC/MS analysis of the derivatized adduct was problematic. A sensitive method was developed for the underivatized compound using LC/ESI/MS/MS, monitoring the fragmentation MH+, m/z 256 —> [CH2CH2SCH2CH2OH]+, m/z 105 on a triple-sector quadrupole instrument (60). LC separation was on a C18 column eluted with water-acetonitrile-formic acid. The detection limit was 8pg injected (S/N 5 1), 0.2 ng/ml in urine. Rao et al. (61) also reported characterization by LC/ESI/MS but using 25 mM NH4HC03 in 20 % MeOH as eluent. [Pg.308]

Analytical methods have been reported for unchanged agent and six of the urinary excretion products described above. These are TDG, TDGO, the bis A-acetylcysteine conjugate (1), two 3-lyase metabolites (2) and (3), and the guanine adduct (6). These methods have been applied to animal and/or human exposures to sulfur mustard. [Pg.409]

The guanine adduct (6) can be isolated from urine by SPE on C18. GC/MS analysis of the adduct was problematic. Derivatization with heptafluorobu-tyric anhydride and pentafluorobenzoyl bromide were unsuccessful and the TBDMS derivative... [Pg.412]

Figure 24.12. Examples of DNA adducts and oxidized guanine nucleotide. (A) Benzo[a]pyrene-7,8-diol-9,10-epoxide-M-2 guanine adduct. (B) Aflatoxin epoxide N7 guanine adduct. (C) 8-Oxoguanine is commonly produced by reactive oxygen species, dR = deoxyribose. Figure 24.12. Examples of DNA adducts and oxidized guanine nucleotide. (A) Benzo[a]pyrene-7,8-diol-9,10-epoxide-M-2 guanine adduct. (B) Aflatoxin epoxide N7 guanine adduct. (C) 8-Oxoguanine is commonly produced by reactive oxygen species, dR = deoxyribose.
Figure 5 Two types of mutations (G->T transversion and C—s-T transition) resulting from the AFBl-N7-guanine adduct [8,9-dihydro-8-(N7 guanyl)-9-hydroxyaflatoxin] Bl. Newly synthesized DNA strand dashed boxes. Figure 5 Two types of mutations (G->T transversion and C—s-T transition) resulting from the AFBl-N7-guanine adduct [8,9-dihydro-8-(N7 guanyl)-9-hydroxyaflatoxin] Bl. Newly synthesized DNA strand dashed boxes.

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See also in sourсe #XX -- [ Pg.307 ]




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