- Stereoselective optical sensing of dicarboxylate anions by an induced- fit type Ru(II) receptor
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An induced-fit type Ru(II) receptor 1 has been synthesized in which, upon approach of dicarboxylates, a highly flexible tetraamide binding site is organized to complement their chemical structures. Stereoselective optical sensing has been demonstrated by virtue of the luminescence response of 1 to the binding of cis/ trans-1,4-cyclohexanedicarboxylates. (C) 2000 Elsevier Science Ltd.
- Watanabe, Shigeru,Higashi, Natsuka,Kobayashi, Michiko,Hamanaka, Kaori,Takata, Yoshiyuki,Yoshida, Katsuhira
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- Synthetic approaches to obtain amino acid adducts of 4,4′- methylenediphenyl diisocyanate
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4,4′-Methylenediphenyl diisocyanate (MDI) is the most important isocyanate used in the chemical industry. Lung sensitization and asthma are the main types of damage after exposure to MDI. Albumin adducts of MDI might be involved in the etiology of sensitization reactions. It is therefore necessary to have sensitive and specific biomarkers such as blood protein adducts to monitor people exposed to isocyanates. For the discovery of new isocyanate adducts with blood proteins present in vivo, new synthetic standards are needed. To achieve this, we developed five methods to obtain amino acid adducts of MDI. We synthesized and isolated MDI adducts of aspartic acid, glutamic acid, cysteine, and valine. The new adducts were characterized by LC-MS/MS and NMR. We synthesized the corresponding isotope-labeled MDI adducts to develop analytical methods using LC-MS/MS. Glutathione adducts of isocyanates are an important way of transportation of the reactive isocyanates to distant sites from the original site of exposure. Therefore, we used N-acetyl-cysteine adducts of MDI as reactants: N-acetyl-S-[[4-(4-aminobenzyl)phenyl]carbamoyl]-cysteine (MDI-AcCys) and N-acetyl-S-[[4-(4-acetylaminobenzyl)phenyl]carbamoyl]-cysteine (AcMDI-AcCys). MDI-AcCys or AcMDI-AcCys formed adducts with albumin, N α-acetyl lysine, and valine. Isotope-labeled albumin adducts (= d4-MDI-albumin) were synthesized from d4-MDI-AcCys and albumin. d4-MDI-albumin can be used as an internal standard to analyze biological samples. Such an internal standard will not correct only for the extraction recovery of the adducts but also for the potential variation of the enzymatic digestions used in the procedure to analyze albumin adducts of MDI. The synthetic procedures described in this manuscript will be applicable to the synthesis of amino acid adducts from other isocyanates.
- Sabbioni, Gabriele,Dongari, Nagaraju,Schneider, Siegfried,Kumar, Anoop
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p. 2704 - 2714
(2013/02/23)
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- Synthesis and quantification of DNA adducts of 4,4'-methylenedianiline
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4,4'-Methylenedianiline (MDA) is used as a hardener in the manufacture of plastics and polyurethanes. MDA has been classified as a carcinogen in animals and is a suspected human carcinogen. Assuming that MDA would yield similar DNA adducts to other arylamines, we synthesized the following C-8 guanine adducts: N'-acetyl-N-(deoxyguanosin-8-yl)-MDA, N-(deoxyguanosin-8- yl)-MDA, N-(deoxyguanosin-8-yl)-4MA, and their corresponding 3'-monophosphate derivatives. We developed methods to identify these adducts of MDA in liver DNA using 32P-postlabeling, HPLC, and GC-MS techniques. Liver DNA was obtained from rats treated with radiolabeled MDA (1.11 and 116.5 μmol/kg body weight). The total radioactivity bound to the DNA corresponded to 0.06 and 2.7 adducts per 107 nucleotides [covalent binding index (CBI = (μmol of adduct per mol of nucleotide)/(mmol of compound per kg body weight)) of 1.05 and 2.3]. This DNA-binding potency is in the range of weakly genotoxic compounds. The liver DNA was analyzed for the presence of the synthesized adducts by the following methods: (I) HPLC analysis of nucleotides and purines after enzymatic and acid hydrolysis, and (II) 32P-postlabeling after enzymatic hydrolysis. The major adducts found in vivo did not correspond to the synthesized standards. Further work was carried out to determine the structure of the unidentified adducts. It was possible to release MDA and MDA-d4 from DNA of rats dosed with MDA and/or MDA-d4 and from the synthesized adducts using strong base hydrolysis. Liver of two female Wistar rats given 500 μmol/kg MDA · 2HCl was hydrolyzed in 0.1 M NaOH overnight at 110 °C. GC-MS analysis of the heptafluorobutyric anhydride derivatized dichloromethane extracts detected 428 ± 40 fmol of MDA/mg of DNA. In the control animals no MDA was found. The experiment was repeated with livers from animals dosed 500 μmol/kg MDA-d4 · 2DCl. In these rats 488 ± 19 final MDA-d4 was found to be bound at liver DNA. Taking into account a 68% yield of the method, the CBI found in these cases was 0.82 and 1.0, respectively.
- Schuetze, Dietrich,Sagelsdorff, Peter,Sepai, Ovnair,Sabbioni, Gabriele
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p. 1103 - 1112
(2007/10/03)
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