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21.
Anibal Mario Nervi Raul Omar Peluffo Rodolfo R. Brenner Alicia Isabel Leikin 《Lipids》1980,15(4):263-268
The effect of ethanol on the fatty acid desaturation by rat liver has been studied using liquid diets of different composition.
Acute ethanol administration increased triacylglycerols of total liver lipids, but did not modify significantly the lipidic
composition of microsomes. The Δ6 and Δ5 desaturases were inhibited by ethanol whereas the Δ9 desaturase and fatty acid synthetase
were apparently modified only by diet composition. NADH-cytochrome (cyt.) c reductase was partially inhibited, whereas NADH-cyt.
b5 reductase remained practically unaltered and NADPH-cyt. c reductase activity was enhanced. Decreased electrons supplied by
the microsomal cyt. b5 electron transport chain would not be the reason for the inhibition of Δ6 and Δ5 desaturases by ethanol. 相似文献
22.
Varying concentrations of free docosa-4,7,10,13,16-pentaenoic acid or its CoA ester were incubated with a given variable concentration
of 1-14C-linoleate or 1-14C-α-linolenate as either the free fatty acid or the CoA ester, microsomal enzymes, and the appropriate cofactors for fatty
acid desaturation. The results obtained were compared to the effects of docosa-4,7,10,13,16,19-hexaenoyl CoA when incubated
in a similar manner in the presence of the labeled substrates. Both feedback and crossed inhibition effects were observed;
these inhibition effects may play a role in the regulation of polyunsaturated fatty acid biosynthesis. 相似文献
23.
The reaction pathway of the ammoxidation of toluene on (VO)2P2O7 used as catalyst and the interaction of potential intermediates with the pyrophosphate were studied by spectroscopic techniques (FTIR, EPR), temperature-programmed chemisorptions/ reactions (TPD, TPRS) and transient studies such as the temporal analysis of products (TAP) technique. NH3 is chemisorbed on the catalyst surface, forming three different species, i.e., NH
4
+
ions located on BrØnsted sites, coordinatively bound NH3 on Lewis sites and NH
2
–
groups, presumably P-NH2. Toluene that is probably adsorbed on Lewis sites reacts in a first step to a benzyl radical. A subsequent partial oxidation by interaction of VIV=O groups generates a V...O=CH-C6H5 surface structure. This benzaldehyde-like surface species reacts with adsorbed NH3 according to a Langmuir-Hinshelwood mechanism. TAP experiments on ammonium-containing vanadium phosphates revealed that NH
4
+
ions could act as potential N-insertion species. No formation of benzylamine as well as the generation of V=NH surface groups as possible intermediates or N-insertion sites were observed. 相似文献
24.
Osvaldo Mercuri N. E. Carrazoni R. R. Brenner 《Journal of the American Oil Chemists' Society》1964,41(2):89-92
Methyl oct-cis-2-enoate was synthesized by selective hydrogenation of methyl oct-2-ynoate at atmospheric pressure with quinoline poisoned palladium as catalyst. The resulting product contained only 7% of thetrans form, as determined by GLC. The structure was confirmed by infrared spectra. Analysis of the infrared spectra is given. The cis andtrans forms of methyl oct-2-enoate were separable by GLC in polar or non-polar columns. GLC runs in polar and non-polar phases showed that the α position of the double bond of methyl oct-2-enoate so affects its properties, that practically no interaction was observed between the double bond and the polar phase. Consequently volatility was the main factor determining the retention times of cis andtrans methyl oct-2-enoate in the polar and non-polar phases studied. 相似文献
25.
Urethanes of cellobiose and cellulose-containing uretdione groups are synthesized by the reaction of aliphatic and aromatic diisocyanate uretdiones with the saccharides. The syntheses are performed as a heterogeneous reaction in dimethyl acetamide using dibutyl tin dilaurate as a catalyst, as well as a homogeneous reaction in dimethyl acetamide-lithium chloride. Thus, Semisynthetic prepolymers are formed that offer the reactivity of (blocked) isocyanate groups. To demonstrate their reactivity, ring opening of the uretdiones is performed by the addition of a secondary amine to yield the corresponding ureas. 相似文献
26.
F. Y. Yan K. A. Gross G. P. Simon C. C. Berndt 《Polymer Engineering and Science》2004,44(8):1448-1459
Polymer‐ceramic composite coatings manufactured from calcium carbonate and ethylene‐methacrylic acid copolymer (EMAA) were prepared via a thermal spray process employing different CaCO3 filler sizes (average size of 2.8, 9 or 36 μm) and loading levels from about 2.5 to 7 wt%. The optimum filler feeding characteristics, deposition efficiency and deposition rate were obtained with a 36 μm sized CaCO3. Tensile properties, peel strength, and the erosion resistance of a pure EMAA and CaCO3‐EMAA composite coatings were investigated. It was found that the tensile strain at fracture of the composite coating decreased with the addition of filler to a greater degree than that observed in compression‐molded polymer composites. This is attributed to an inhomogenous distribution of the filler, with more being concentrated at the boundaries of the deposited polymer particles, thereby establishing a rigid framework within the coating. Only a small filler content is necessary to establish large changes in the mechanical properties of the coating. The peel strength of a composite coating decreases with filler content, both on a mild steel substrate and a previously sprayed polymer coating. Bonding to the latter is significantly higher and offers a possibility as a bonding layer between substrates and composite coatings. The coefficient of friction is lowered with the addition of a filler. Erosion testing has shown that the erosion resistance of PF111 is little improved overall with filler addition, although some increase is found for filler contents less than 5 vol%. Polym. Eng. Sci. 44:1448–1459, 2004. © 2004 Society of Plastics Engineers. 相似文献
27.
The catalytic activity and selectivity of three PdO-MoO3/-Al2O3 catalysts containing about 2% Pd and 2% Mo were studied for the reduction of NO by h2 in the presence of varying amounts of oxygen at temperatures from 50 to 550 °C. The results are compared with those for PdO/-Al2O3, PdO-MoO3/-Al2O3 containing 2% Pd and 20% Mo, and a commercial Pt-Rh catalyst. In the absence of oxygen, the conversion of NO to N2 and N2O is higher on the three catalysts than it is on PdO/-Al2O3 at 500 and 550 °C. In the presence of oxygen, the yields of N2 and N2O are generally lower on two of the PdO-MoO3/-Al2O3 catalysts than on PdO/-Al2O3. 相似文献
28.
Ammonium phosphate slurries are produced from impure phosphoric acid that contains Fe(III), Al(III) and Mg(II) ions. The insolubility of these metal ions and the onset of solid formation determined as a function of pH or mole ratio (MR) of ammonia to phosphoric acid were consistent with the trend for the pH of formation of the first hydrolysis product that decreases in the following order: Fe(III)<Al(III)<Mg(II). The hydrolysis products of Fe(III) formed at pH>2.0 or MR>0.5 initiate ammonium phosphate crystallization, reduce the size of particles formed and generate attractive interparticle forces. Similarly, the Al(III) hydrolysis products formed later at pH>2.6 MR>0.7), will also initiate further crystallization, adsorb on particles and produce attractive forces. The attractive forces and the high number concentration of particle—particle interactions are responsible for the increased viscosity and non-Newtonian flow behavior displayed at increasing Fe(III) and Al(III) concentration. Mg(II) ions are not hydrolyzed at MR<1.0 so its effect on rheology is negligible and its effect at MR<1.0 is also small as its concentration is much smaller than that of Fe(III) and Al(III) ions. The change in slurry viscosity with the degree of neutralization is also explained in terms of particle size distribution, solubility and solids concentration variations. 相似文献
29.
The effect of oral administration, for 24 or 48 hr, of different octadeca fatty acids containing a 9,12-dienoic structure
on the fatty acid composition and Δ9 desaturation activity of liver microsomes of rat fed a fat-free diet was studied. The
ethyl esters of linoelaidic and γ-linolenic acids, the methyl ester of linoleic acid and free columbinic acid were administered
to rats maintained on a fat-free diet. The supplementation of the fat-free diet with linoelaidate produced no relevant changes
in the fatty acid composition pattern of liver microsomes and did not modify the percentage of conversion of palmitic to palmitoleic
acid. The addition of linoleate or γ-linolenate to the fat-free diet returned liver microsome Δ9 desaturation activity toward
the control and partially restored the liver microsome fatty acid spectrum found in the fat-free diet. Columbinic acid (5-trans-9-cis,12-cis-18∶3), which cannot be transformed into arachidonic acid, also decreased the Δ9 desaturation activity enhanced by the fat-free
diet and evoked changes in the microsomal fatty acid composition similar to those produced by the ω6 fatty acids. These results
suggest that the modulation of Δ9 desaturase activity evoked by dietary administration of unsaturated acids of ω6 series would
depend on thecis double bond configuration of these acids. 相似文献
30.
The incorporation of L-4,5-[3H]leucine into the ultracentrifugally separated apolipoproteins of very low, low, and high density lipoproteins (VLDL, LDL,
HDL) and into serum albumin was found three-to four-fold higher in nephrotic than in normal rats one hour after intravenous
injection. Incorporation of leucine into the circulating lipids was negligible. Increases of similar magnitude were obtained
in the incorporation of simultaneously injected 1,5[14C] citrate into the lipids of VLDL, LDL, and HDL of nephrotic rats. Of the citrate carbons incorporated into serum and liver
lipids, the proportion in cholesterol was higher in nephrotic rats when compared to normal rats. The incorporation of both
precursors into total proteins and lipids of the liver vs. the incorporation into the lipoproteins was relatively lower in
nephrotic than in control rats, indicating a preferential channeling into secretable products. The occurrence of enhanced
new lipid synthesis in nephrosis was corroborated by the finding of markedly enhanced synthesis of lipoprotein-borne fatty
acids and cholesterol from3H2O. These results point out that while leucine is not an efficient in vivo precursor of lipoprotein lipids in nephrosis, de
novo lipogenesis proceeds from other precursors. Similar trend of changes, though of smaller magnitude, was elicited in rats
after double plasmapheresis, 18 hr apart, when measured 3 hr after the second plasma withdrawal. This indicates that the loss
of circulating proteins either by direct removal or through kidney lesion stimulates the compensatory hepatic response involving
excessive lipoprotein synthesis. Time-course studies showed that peak incorporation of leucine and citrate into the protein
and lipid components of lipoproteins, respectively, as well as into serum albumin, occurred coincidentally 3 hr after the
second plasmapheresis, suggesting an interdependence of the enhanced protein and lipid synthesis. 相似文献