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.

Propionyl-CoA synthetase in mammary gland and liver of cows.

Propionyl-CoA synthetase of liver and mammary gland from calf and midlactation cow was investigated. No activity of this enzyme was detected in calf mammary gland, but it was detected in calf liver. Propionyl-CoA synthetase was found in both, liver and mammary gland of the cow, although mammary gland activity was about 25% of that found in liver. The effects of pH and temperature on enzyme activity and stability were also investigated in crude extracts of liver and mammary gland tissues. The results suggest a different behaviour of the enzyme from both origins. Kinetic studies of the enzyme were also carried out, showing differences, depending on the organ, in the apparent substrate KM values.

Comparative analysis of propionyl-CoA carboxylase from liver and mammary gland of mid-lactation cow.

1. Propionyl-CoA carboxylase from mid-lactation cow liver and mammary gland has been purified. 2. In both organs, the molecular mass was estimated to be approximately 450 kD, and two molecular subunits of 77 and 64 kD could be observed. 3. Physico-chemical and kinetical properties for the enzyme from both organs were similar, showing an allosteric behaviour in relation to ATP and Mg2+. 4. The presence of propionyl-CoA carboxylase in mid-lactation cow mammary gland with similar properties to the liver enzyme, could indicate the existence of a gluconeogenic metabolism in this organ exactly when a high demand of glucose for milk lactose is required.

[Partial purification and biological activity of liver metallothionein]. / Purificación parcial y actividad biológica de la metalotioneína hepática.

The hepatic metallothionein was isolated and partially purified from rats treated previously with stable Cl2Cd and Cl2Cd109. The livers were subjected to the extraction of proteins of low relative molecular weight by heat, ammonium sulphate, Sephadex G-25 and Sephadex G-75. The partially purified extracts were subjected to the pharmacological activity test on isolated mouse vas deferens. A specific effect on the norepinephrine synapsis was obtained through an increment of the answer to the electric stimulus. The mechanism of action could be explained by the increase of the calcium permeability through the membrane or by the increment of the norepinephrine presynaptic release.