FTIR gas-phase kinetic study on the reactions of some acrylate esters with OH radicals and Cl atoms.

Acrylate esters are α,ß-unsaturated esters that contain vinyl groups directly attached to the carbonyl carbon. These compounds are widely used in the production of plastics and resins. Atmospheric degradation processes of these compounds are currently not well understood. The kinetics of the gas phase reactions of OH radicals with methyl 3-methylacrylate and methyl 3,3-dimethylacrylate were determined using the relative rate technique in a 50 L Pyrex photoreactor using in situ FTIR spectroscopy at room temperature (298 ± 2 K) and atmospheric pressure (708 ± 8 Torr) with air as the bath gas. Rate coefficients obtained were (in units cm(3) molecule(-1) s(-1)): (3.27 ± 0.33) × 10(-11) and (4.43 ± 0.42) × 10(-11), for CH3CH═CHC(O)OCH3 and (CH3)2CH═CHC(O)OCH3, respectively. The same technique was used to study the gas phase reactions of hexyl acrylate and ethyl hexyl acrylate with OH radicals and Cl atoms. In the experiments with Cl, N2 and air were used as the bath gases. The following rate coefficients were obtained (in cm(3) molecule(-1) s(-1)): k3 (CH2═CHC(O)O(CH2)5CH3 + Cl) = (3.31 ± 0.31) × 10(-10), k4(CH2═CHC(O)OCH2CH(CH2CH3)(CH2)3CH3 + Cl) = (3.46 ± 0.31) × 10(-10), k5(CH2═CHC(O)O(CH2)5CH3 + OH) = (2.28 ± 0.23) × 10(-11), and k6(CH2═CHC(O)OCH2CH(CH2CH3)(CH2)3CH3 + OH) = (2.74 ± 0.26) × 10(-11). The reactivity increased with the number of methyl substituents on the double bond and with the chain length of the alkyl group in -C(O)OR. Estimations of the atmospheric lifetimes clearly indicate that the dominant atmospheric loss process for these compounds is their daytime reaction with the hydroxyl radical. In coastal areas and in some polluted environments, Cl atom-initiated degradation of these compounds can be significant, if not dominant. Maximum Incremental Reactivity (MIR) index and global warming potential (GWP) were also calculated, and it was concluded that these compounds have significant MIR values, but they do not influence global warming.

Night-time atmospheric chemistry of methacrylates.

BACKGROUND, AIM, AND SCOPE: Methacrylates are α, ß-unsaturated esters that are widely used in the polymer plastics and resins production. Kinetic information of NO(3) radical reactions is especially scarce and a good understanding of all the atmospheric oxidation processes of these compounds is necessary in order to determine lifetimes in the atmosphere and to evaluate the impact of these reactions on the formation of ozone and other photooxidants. MATERIALS AND METHODS: The experiments have been carried out using the relative technique in a static Teflon reactor at room temperature and atmospheric pressure (N(2) as bath gas) using gas chromatography (GC)-flame ionization detection (FID) as detection system. Products were analyzed using solid phase microextraction (SPME)-GC-mass spectrometry (MS) technique and Fourier transform infrared spectroscopy (FTIR) using air as bath gas. RESULTS: The following rate coefficients were obtained (in cm(3) molecule(-1) s(-1)): methyl methacrylate + NO(3) = (3.55 ± 0.62) × 10(-15), ethyl methacrylate + NO(3) = (5.42 ± 1.90) × 10(-15), butyl methacrylate + NO(3) = (7.87 ± 3.86) × 10(-15). Methylpyruvate, ethylpyruvate, and butylpyruvate/butanol were identified as main degradation products respectively in the GC-MS analysis. Nitrates compounds were also identified in the FTIR study. DISCUSSION: The reactivity increases with the substitution and with the chain of the alkyl group in -C(O)OR. An electrophilic addition mechanism is proposed as dominant degradation process. Estimations of the atmospheric lifetimes clearly indicate that the dominant atmospheric loss process for methacrylate esters is their daytime reaction with the hydroxyl radical. NO(3) and ozone are the main oxidants at night time. RECOMMENDATIONS AND PERSPECTIVES: A detailed products analysis including quantification could elucidate the mechanism for butanol generation for butyl methacrylate reaction.

Regulation of the pentose phosphate cycle in bass (Dicentrarchus labrax L.) liver.

The influence in the activities of the glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase produced by the ratio changes NADPH/NADP is studied. The intracellular ratios of 20 and 10 are enough to achieve total inhibition of these two enzymes, respectively. Measurements of a number of metabolic intermediates show that the concentrations of Krebs cycle compounds are higher than those of glycolytic pathway metabolites. From a consideration of these values, the regulation of the pentose phosphate cycle mainly by the intracellular NADPH/NADP ratio, is discussed.

Purification of 6-phosphogluconolactonase from bass (Dicentrarchus labrax L.)liver.

The enzyme 6-phosphogluconolactonase (EC 3.1.1.31) is present at high levels in bass liver. The enzyme has been purified 1253-fold with an overall yield of 78% in a procedure involving dye-ligand and gel filtration chromatographies. The purified enzyme which is homogenous by all the usual criteria has a molecular weight of about 30,000. It exhibits a considerably high catalytic efficiency with Kcat/Km of 8.5 x 10(7) M-1.s-1 at 22 degrees C. Its activity illustrates the importance of glucose oxidation via the pentose phosphate pathway relative to glycolysis in this organism.

Bass liver 6-phosphogluconate dehydrogenase: inhibition by nucleoside phosphates and by fructose 1,6 bisphosphate.

Nucleoside 5'-triphosphates, 5'-diphosphates and 5'-monophosphates are inhibitors of the 6-phosphogluconate dehydrogenase enzyme from bass liver. The 2'- and 3'-monophosphates of adenosine and guanosine are also inhibitory, the 2'-isomers being especially potent inhibitors. The catalytic activity of 6-phosphogluconate dehydrogenase has been found to be markedly inhibited by fructose 1, 6 bisphosphate. As the Km for 6-phosphogluconate, the Ki for fructose 1,6 bisphosphate and the concentration of both compounds in bass liver are all comparable, it appears that the inhibition of 6-phosphogluconate dehydrogenase by fructose 1,6 bisphosphate may be of significance in the regulation of carbohydrate metabolism in bass liver.

NADP-dependent isocitrate dehydrogenase from bass (Dicentrarchus labrax L.) liver.

The isocitrate dehydrogenase from bass liver was purified to homogeneity by gel filtration, affinity and ion exchange chromatographies. The molecular weight was estimated by gel filtration chromatography to about 120,000. Analysis of the enzyme on sodium dodecyl sulphate polyacrylamide gel electrophoresis showed it to be a dimeric protein. The enzyme showed maximum activity in the pH range between 7.0 and 8.0 while its maximum activity was at pH 7.5. DL-Isocitrate and Mn2+ stabilized the enzyme, while NADP had the opposite effect. The Km for isocitrate was 0.31 mM and the Km for NADP was 36 microM.

Kinetic analysis of 6-phosphogluconate dehydrogenase from bass liver: effects of temperature and pH on its catalytic function.

Kinetic studies of the reaction between 6-phosphogluconate and NADP catalyzed by purified 6-phosphogluconate dehydrogenase from bass liver were made at pH 7.5 in Tris-HCl buffer. Relationships among the initial rate coefficients for 6-phosphogluconate, NADP, and Mg2+ suggest that the addition of Mg2+ and NADP to 6-phosphogluconate dehydrogenase does not follow an obligatory order, probably being random, in which 6-phosphogluconate combines second with the enzyme. The Michaelis constants for NADP, 6-phosphogluconate, and Mg2+ are 0.88 microM, 26.66 microM, and 3.33 mM, respectively. pK values for the enzyme-6-phosphogluconate and enzyme-NADP complexes have been obtained. The variations in the true Km values for NADP with pH are only threefold at most, and seem to be not especially significant. A plausible explanation for the physiological significance of the influence of temperature on the Km values is given. Kinetic studies show that phosphoenolpyruvate is a noncompetitive inhibitor of the enzyme with respect to 6-phosphogluconate and a competitive inhibitor with respect to NADP with Ki values of 0.54 mM against 6-phosphogluconate and 0.15 mM against NADP.

Kinetic properties from bass liver 6-phosphogluconolactonase.

By specific enzymic synthesis of the substrate 6-phosphogluconolactone "in situ", the Km for bass liver 6-phosphogluconolactonase was found to be 90 microM. This value is compatible with the kinetic parameters of both glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase from bass liver, and hence with the flux through the oxidative phase of the pentose phosphate pathway.

Dieldrin transformation to photodieldrin in liver and kidney of broiler.

Dieldrin, a potent residual insecticide and common contaminant of the environment, is metabolized in liver and kidney of broiler to photodieldrin, a photoisomer of dieldrin. This metabolite has by gas-liquid chromatography (g.l.c.) analysis a retention time different to the aldrin. The analysis by thin-layer chromatography (t.l.c.) of metabolite shows an Rf of 0.37. The i.r. (infra-red) spectrum shows the band corresponding to the epoxide ring (800-1300 cm-1) and does not show the characteristics bands of C = O (1800 cm-1) and ClC = CCl (1600 cm-1).

Factors in the accumulation of dieldrin in broiler organs: doses administered with feed; dose-organ-dieldrin accumulated relationship; toxicological consequences.

The quantity of dieldrin accumulated in liver, kidney, heart, gizzard, lung, muscle, and intestine with contents, of broiler chickens fed with feed contaminated by this insecticide, was determined by gas chromatography analysis. The doses used were 60, 90, 120, 200 and 240 ppm. The influence of the doses used in the quantity of dieldrin accumulated in the different organs, the relationship between the doses administered, organs and quantity accumulated, and the toxicological consequences of the contamination were studied. The results show that the doses used did not significantly affect the quantity of dieldrin accumulated by the different organs. The relationship doses-organ-quantity accumulated shows that the muscle accumulates equal dieldrin at all the doses used. The differences in the dieldrin accumulated at different doses increases with the metabolic function of the organs. The principal symptoms of intoxication were anorexia, convulsions and tremors, which indicated that the nervous system is a major site of activity.

Properties and function of mitochondrial malate enzyme from bass liver.

Malate enzyme (L-malate: NADP+ oxidoreductase oxaloacetate decarboxylating, EC 1.1.1.40) from bass liver mitochondria was purified to over 90% of homogeneity by gel filtration, affinity and ion exchange chromatographies. The apparent molecular weight estimated by gel filtration was 316,000. Analysis of the enzyme on sodium dodecylsulphate-polyacrylamide disc gel electrophoresis was shown to be a tetramere protein. The enzyme required bivalent cations for catalysis, (Mn2+ or Mg2+) and displayed a narrow pH optimum (8.4-8.6 for Tris-HCl buffer) and was inactivated by p-chloromercuribenzoate. The double reciprocal initial velocity plots of both of the substrates, NADP and malate, were linear and intercepting at a point that suggests a sequential mechanism. Product inhibition studies with NADP and malate as variable substrate are consistent with an ordered Bi-Ter mechanism.

Factors in the accumulation of dieldrin in broiler organs: quantity ingested, sex and weight of animal.

The effect of several factors in relation to the quantities of dieldrin accumulated in different organs of broilers was studied. Feedstuff was contaminated at doses of 60, 90, 120, 200 and 240 ppm. With the doses used, the results show an accumulation summit over which the amounts accumulated are not affected by greater quantities of dieldrin ingested. The accumulation of dieldrin in the female is greater than in the male and the weight of the animal does not significantly affect the response.