Detecting exposure-dependent changes of liver detoxification capacity of children in a formerly high-loaded industrial area with a 15N-labelled diagnostic tool

The effect of remediation activities in formerly high-loaded industrial areas is measured conventionally in terms of decreased toxic loads. It is more difficult to investigate the effect on physiological parameters of the people living there. A non-invasive 15N-based organ function test, the [15N]methacetin urine test, was adapted to environmental-medical purposes for the detection of small deviations from the norm-range hepatic detoxification capacity. Parallel to the measurement of region-specific external exposure (especially by tri- and tetrachloro ethylene) and of the corresponding internal load (urinary trichloro acetic acid), the hepatic mono oxygenation capacity was determined. The study cohort consisted of 35 kindergarten children who were 3.3+/-0.5 years old at the beginning of the study. They lived in a high-polluted industrial village (n = 23) and in a non-polluted control village close by (n = 12), respectively. Children living in the polluted area were exposed a 2.3 times higher load and showed detoxification capacities 6% lower than the children in the control area. Improvement of the environmental situation led to exposure data decreasing by 70%, which is also reflected in smaller internal load and improved liver detoxification of the children in the polluted area. Then, between loaded and control area the mean hepatic detoxification was no longer significantly different (0.6%). The study shows that chronic low-dose exposure can disturb a hepatic function and that thereafter the capacity is recovered quickly in children. The stable isotope-based test is suited to characterize a health effect of multicomponent exposure by bioeffect monitoring within the framework of screening and testing the remediation efficiency.     

Effects of gemini surfactants on egg phosphatidylcholine bilayers in the fluid lamellar phase

The influence of 1,4-butanediamonium-N,N'-dialkyl-N,N,N',N'-tetramethyl dibromides (CmA, m = 7-16 is the number of alkyl carbons) on the egg yolk phosphatidylcholine (EYPC) bilayer thickness and lipid surface area at the bilayer-aqueous phase interface is studied using X-ray diffraction on fluid lamellar CmA + EYPC + H2O phases as a function of CmA:EYPC and H2O:EYPC molar ratios and the alkyl chain length m. At the constant CmA:EYPC = 0.4 and H2O:EYPC = 18 molar ratios, the CmA induced bilayer thickness decrease shows a minimum and the lipid surface area increase a maximum at the alkyl chain length m = 9. The obtained results are discussed in the context of a structural perturbation model of the cut-off effect in biological potencies of surfactants which occurs when increasing the alkyl substituent chain length above the critical value.     

Reexamination of CeCl3 and InCl3 as activators in the diastereoselective Mukaiyama aldol reaction in aqueous media

A search for suitable reaction conditions in Mukaiyama-type aldol condensations activated by CeCl(3) and InCl(3) revealed that the reaction proceeds best in i-PrOH/H(2)O (95:5). Contrary to literature precedent, no reaction was observed in pure water, and the encountered destruction of the starting silyl enol ether can be ascribed to initial hydrolysis of the Lewis acid. As anticipated from the dual parameter (pK(h), WERC value) characteristics of CeCl(3) and InCl(3), the former proved more efficient as Lewis acid-promoter, in terms of reaction speed and yield. Nevertheless, InCl(3) was a superior catalyst during evaluation of the diastereoselectivity of the process. In this regard, determination of diastereoselectivity as a function of time showed that the InCl(3)-catalyzed reaction is irreversible, whereas the CeCl(3)-catalyzed reaction is a reversible process. In both cases, formation of the syn product is kinetically preferred, although DeltaDeltaG(++)273K(InCl(3)) = 1.50 kcal/mol versus DeltaDeltaG(++)273K (CeCl(3)) = 0.38 kcal/mol. Molecular modeling (semiempirical PM3, ab initio HF/3-21G*, hybrid B3LYP/3-21G*, and B3LYP/LANL2DZ) of the diastereoselective aldol reaction promoted by InCl(3) supports a "closed", Zimmermann-Traxler transition state.     

Dioxygenase-catalysed oxidation of monosubstituted thiophenes: sulfoxidation versus dihydrodiol formation

Toluene dioxygenase (TDO)-catalysed sulfoxidation, using Pseudomonas putida UV4, was observed for the thiophene substrates 1A-1N. The unstable thiophene oxide metabolites, 6A-6G, 6K-6N, spontaneously dimerised yielding the corresponding racemic disulfoxide cycloadducts 7A-7G, 7K-7N. Dimeric or crossed [4 + 2] cycloaddition products, derived from the thiophene oxide intermediates 6A and 6D or 6B and 6D, were found when mixtures of thiophene substrates 1A and 1D or 1B and 1D were biotransformed. The thiophene sulfoxide metabolite 6B was also trapped as cycloadducts 17 or 18 using stable dienophiles. Preferential dioxygenase-catalysed oxidation of the substituent on the thiophene ring, including exocyclic sulfoxidation (1H-1J) and cis-dihydroxylation of a phenyl substituent (1G and 1N), was also observed. An enzyme-catalysed deoxygenation of a sulfoxide in P. putida UV4 was noticed when racemic disulfoxide cyclo-adducts 7A, 7B and 7K were converted to the corresponding enantioenriched monosulfoxides 8A, 8B and 8K via a kinetic resolution process. The parent thiophene 1A and the 3-substituted thiophenes 1K-1N were also found to undergo ring dihydroxylation yielding the cis/trans-dihydrodiol metabolites 9A and 9K-9N. Evidence is provided for a dehydrogenase-catalysed desaturation of a heterocyclic dihydrodiol (9Kcis/9Ktrans) to yield the corresponding 2,3-dihydroxythiophene (24) as its preferred thiolactone tautomer (23). A simple model to allow prediction of the structure of metabolites, formed from TDO-catalysed bacterial oxidation of thiophene substrates 1, is presented.     

Simultaneous reversible addition fragmentation chain transfer and ring‐opening polymerization

The simultaneous ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL) and 2‐hydroxyethyl methacrylate (HEMA) polymerization via reversible addition fragmentation chain transfer (RAFT) chemistry and the possible access to graft copolymers with degradable and nondegradable segments is investigated. HEMA and ε‐CL are reacted in the presence of cyanoisopropyl dithiobenzoate (CPDB) and tin(II) 2‐ethylhexanoate (Sn(Oct)₂) under typical ROP conditions (T > 100 °C) using toluene as the solvent in order to lead to the graft copolymer PHEMA‐g‐PCL. Graft copolymer formation is evidenced by a combination of size‐exclusion chromatography (SEC) and NMR analyses as well as confirmed by the hydrolysis of the PCL segments of the copolymer. With targeted copolymers containing at least 10% weight of PHEMA and relatively small PHEMA backbones (ca. 5,000–10,000 g mol^?1) the copolymer grafting density is higher than 90%. The ratio of free HEMA‐PCL homopolymer produced during the “one‐step” process was found to depend on the HEMA concentration, as well as the half‐life time of the radical initiator used. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3058–3067, 2008