Trimethylamine N-oxide (TMAO), as a gut-derived metabolite, has been found to be associated with enhanced risk for atherosclerosis and cardiovascular disease. We presented a method for targeted profiling of TMAO and betaine in serum and food samples based on a combination of one-step sample pretreatment and proton nuclear magnetic resonance spectroscopy. The key step included a processing of sample preparation using a selective solid-phase extraction column for retention of basic metabolites. Proton signals at δ 3.29 and δ 3.28 were employed to quantify TMAO and betaine, respectively. The developed method was examined with acceptable linear relationship, precision, stability, repeatability, and accuracy. It was successfully applied to detect serum levels of TMAO and betaine in TMAO-fed mice and high-fructose-fed rats and also used to determine the contents of TMAO and betaine in several kinds of food, such as fish, pork, milk, and egg yolk. 相似文献
Catalysis Surveys from Asia - Benzene methylation over zeolite offers an alternative route to produce high-value toluene or para-xylene directly from benzene and C1 chemical sources, especially for... 相似文献
In this paper, chitooligosaccharides in different salt forms, such as chitooligosaccharide lactate, citrate, adipate, etc., were prepared by the microwave method. They were characterized by SEM, FTIR, NMR, etc., and the nitric oxide (NO) expression was determined in RAW 264.7 cells. The results showed that pure chitooligosaccharide was an irregular spherical shape with rough surface, and its different salt type products are amorphous solid with different honeycomb sizes. In addition to the characteristic absorption peaks of chitooligosaccharides, in FTIR, the characteristic absorption of carboxyl group, methylene group, and aromatic group in corresponding acid appeared. The characteristic absorption peaks of carbon in carboxyl group, hydrogen and carbon in methyl, methylene group, and aromatic group in corresponding acid also appeared in NMR. Therefore, the sugar ring structure and linking mode of chitooligosaccharides did not change after salt formation of chitooligosaccharides. Different salt chitooligosaccharides are completely different in promoting NO secretion by macrophages, and pure chitooligosaccharides are the best. 相似文献
Diisopropyl ether (DIPE) is considered as a promising gasoline additive due to the favorable blending Reid vapor pressure and the low water solubility. To get a good understanding of the DIPE oxidation chemistry, oxidation experiments of a stoichiometric mixture of DIPE/O2/Ar/Kr were performed in a jet-stirred reactor (JSR) at atmospheric pressure over the temperature range of 525–900 K in this work. About 30 intermediates and products were identified and quantified using a photoionization molecular-beam mass spectrometer (PI-MBMS). Furthermore, a detailed kinetic model was proposed for DIPE oxidation, which showed satisfactory performances in predicting the species concentration profiles in this work as well as those in literature. For DIPE oxidation, the fuel consumption was observed only above 750 K, even though DIPE has two tertiary hydrogen atoms that are easy to be abstracted so that low-temperature oxidation reactivity is expected. The low oxidation reactivity at low temperature is because the formed OOQOOH radical mostly dissociates back to QOOH+O2, instead of undergoing intramolecular isomerization which leads to the low-temperature chain-branching. At higher temperature, DIPE is mainly consumed by hydrogen abstraction reactions from the carbon atoms adjacent to the oxygen atom, producing dominantly the IC3H7OC(CH3)2 fuel radical, which then decomposes rapidly via CO bond β-scission instead of combining with O2. In contrast, the minor fuel radical IC3H7OCH(CH3)CH2 tends to go through the O2 addition reaction and the subsequent chain branching reactions, as confirmed by the detection of cyclic ether intermediates. Propylene and acetone are the most abundant intermediates in DIPE oxidation, both of which predominantly come from the initial fuel decomposition steps. Other intermediates are mainly formed via the consumption of these two species. 相似文献
In this paper, a single reaction-diffusion population model with memory effect and the heterogeneity of the environment, equipped with the Neumann boundary, is considered. The global existence of a spatial nonhomogeneous steady state is proved by the method of super and subsolutions, which is linearly stable for relatively small memory-induced diffusion. However, after the memory-induced diffusion rate exceeding a critical value, spatial inhomogeneous periodic solution can be generated through Hopf bifurcation, if the integral of intrinsic growth rate over the domain is negative. Such phenomenon will never happen, if only memory-induced diffusion or spatially heterogeneity is presented, and therefore must be induced by their joint effects. This indicates that the memory-induced diffusion will bring about spatial-temporal patterns in the overall hostile environment. When the integral of intrinsic growth rate over the domain is positive, it turns out that the steady state is still linearly stable. Finally, the possible dynamics of the model is also discussed, if the boundary condition is replaced by Dirichlet condition.
The synthesis of hyper-branched ethene oligomers through catalytic insertion reactions with late transition metal catalysts is unique in its synthetic and practical scope. In this study, a series of iminopyridyl Ni(II) and Pd(II) complexes with electron-rich distal aryl motifs were synthesized and characterized. These complexes were very efficient in ethene oligomerization and co-oligomerization with methyl acrylate (MA). Hyperbranched ethene oligomers with different microstructures were generated using different metal species in ethene oligomerization. More importantly, hyperbranched ethene-MA co-oligomers with varying incorporation ratios were generated via ethene and MA co-oligomerization using the Pd(II) complexes. Most notably, weak neighboring group interactions of distal aryl motifs in the nickel system are more effective in influencing the microstructure of ethene oligomers than the corresponding palladium system. 相似文献