Application of chromium catalysis technology to compound-specific hydrogen isotope analysis of natural gas samples.

An easy-to-use and efficient approach for the catalytic pyrolysis of hydrocarbon gas here is proposed and tested, which allowed the precise measurement of δ2H. This method requires the reaction tube filled with twisted chromium wire, establishing a gas chromatography-Chromium wire/high temperature conversion-isotope ratio mass spectrometer (GC‒Cr/HTC‒IRMS) system. The approach described here has many remarkable advantages over other techniques. In comparison to traditional carbon-coating pyrolysis technique, this proposed method greatly reduces the pyrolysis temperature of the hydrocarbon gas, especially methane, with temperatures reduced from 1450 to 1250 °C, while still ensuring excellent analytical precision. Therefore, hydrogen isotope analysis of natural gas can be carried out at a lower cracking temperature for a longer time, with the advantage of increasing the service life of the HTC furnace. Meanwhile, no pretreatment or activation is required while putting the Cr/HTC system to use. Further, the accuracy of δ2H values obtained using this new method is better than using the traditional method. Our experiments demonstrate that the test errors of this novel method and the conventional method are within ±5.5‰ and ±6.5‰, respectively.

An ultra-sensitive selective fluorescent sensor based on a 3D zinc-tetracarboxylic framework for the detection and enrichment of trace Cu2+ in aqueous media.

Herein, a novel and fluorescent zinc-organic framework sensor [Zn3(µ3-Hbptc)2(µ2-4,4'-bpy)2(H2O)4]n·2nH2O (1) (H4bptc = 2,3,3',4'-biphenyl tetracarboxylic acid, 4,4'-bpy = 4,4'-bipyridine) is synthesized and characterized, demonstrating its excellent fluorescence performance for Cu2+ detection and the enrichment of Cu2+ in aqueous media. The fluorescence intensity of 1 can be selectively quenched by Cu2+ in a linear range of Cu2+ concentrations of 0-0.7 µM. The limit of detection (LOD) value is as low as 32.4 nM, which is superior to those of most of the fluorescent sensors based on metal-organic frameworks (MOFs). It is also far below the maximum allowable concentration of Cu2+ in drinking water as defined by the U.S. Environmental Protection Agency (EPA) and the World Health Organization (WHO), so it is employed for the detection of Cu2+ in actual water samples. More importantly, the nature of the interaction between the active coordination site (COO-) of 1 and Cu2+ determines the quenching mechanism, that is Cu2+ in the analyte is captured by MOF 1, which has been investigated by ICP, luminescence, UV-vis, XPS, and lifetime studies. Besides, the chemosensor shows regeneration performance without the loss of performance in five consecutive cycles. So MOF 1 is a simple and convenient probe used not only for the rapid detection but also for the enrichment of trace amounts of Cu2+ in aqueous media, and the application can be further extended to a variety of environmental and biological analysis processes.

[Molecular and Carbon Isotopic Compositions of n-Alkanoic Acids in Smoke from Maize Straw Combustion].

Four cultivars of maize straw were burned under flaming and smoldering conditions. Smoke samples were colleted and analyzed by GC/MS and GC/C/IRMS to determine molecular and stable carbon isotopic compositions of n-alkanoic acids in them. The results showed that n-alkanoic acids in flaming smoke were composed of C7 to C34, with a mean total content of 13895.0 mg·kg-1. The average ratio values of the content for homologues with lower carbon number (≤C16) to that for ones with higher carbon number (>C16) (L/H), C18/C16, C24/C16, C24/C18, and C24/(C22+C26) (CAR) were 1.1, 0.33, 0.17, 0.50, and 1.2, respectively. Moreover, the acids exhibited a bimodal profile with peaks at C16 and C24, respectively. They had evident even to odd carbon number predominance (mean CPI: 4.5). In smoldering smoke the acids were consisted of C6 to C34, with an average total content of 50183.7 mg·kg-1. The mean ratios of L/H, C18/C16, C24/C16, C24/C18, and CAR were 1.3, 0.33, 0.20, 0.60, and 1.6, respectively. In addition, the homologues had the same distribution pattern as in flaming smoke and even to odd carbon number predominance (mean CPI=6.1). The mean carbon isotopic ratio (δ13 C) values for individual n-alkanoic acids (C14 to C26) in flaming smoke ranged from -21.0‰ to -24.8‰, the overall average of which was -23.5‰. The difference between mean δ13 C values of n-fatty acids in flaming smoke and the straw (Δ13 C) was -0.7‰. In smoldering smoke, the mean δ13 C values for the compounds varied from -21.8‰ to -25.4‰, with an overall average of -23.3‰. The Δ13 C value was up to -0.5‰. The molecular and carbon isotopic compositions of n-alkanoic acids in smoke were significantly different from those in straw matter. L/H, C24/C16, C24/C18, CAR, and δ13 C might be useful proxies to discriminate the organic pollutants in atmospheric aerosols derived from maize straw combustion.

Natural Products on Nonalcoholic Fatty Liver Disease.

Non-alcoholic fatty liver disease (NAFLD) is a chronic disorder of lipid and carbohydrate metabolism and is often associated with endoplasmic reticulum stress, energy homeostasis dysregulation, and inflammation at cellular and molecular levels. Use of currently available anti-hyperlipidemia, hypoglycemia, or anti-inflammation drugs to treat NAFLD has not achieved desirable outcomes. A growing attention thus has been paid towards natural products as an alternative means in treating NALFD. Some of the natural products apparently possess the properties of ameliorating symptoms of NAFLD through restoration of lipid and carbohydrate metabolism and energy homeostasis. Data from recent animal and human studies concerning the use of natural products in the treatment of NAFLD are analyzed, and the potential underlying mechanisms are discussed.

Recent insights into farnesoid X receptor in non-alcoholic fatty liver disease.

Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome and is one of the most prevalent liver disorders worldwide. NAFLD can gradually progress to liver inflammation, fibrosis, cirrhosis and even hepatocellular carcinoma. However, the pathogenesis of NAFLD is complex, and no efficient pharmaceutic treatments have yet been established for NAFLD. Accumulating data have shown that the farnesoid X receptor (FXR) plays important roles not only in bile acid metabolism, but also in lipid and carbohydrate homeostasis, inflammatory responses, among others. In this review, we aim to highlight the role of FXR in the pathogenesis and treatment of NAFLD.

[An analysis of subhealth status based on partial least squares].

OBJECTIVE: To explore the discrimination model of subhealth with statistical method of partial least squares (PLS). METHODS: This study was based on the Subhealth State Rating Scale (SHSRS). A total of 88 subhealth subjects (scoring less than 85 in SHSRS) and 64 healthy people (scoring over 85 in SHSRS) were enrolled randomly. Information regarding the clinical symptoms was screened by stepwise regression as independent variables. Mathematical models were established by leave-one-out in PLS program for subhealth recognition before and after stepwise regression respectively. Accuracy rates were observed and compared by using the Visual Basic 6.0. RESULTS: The practical accuracy rate of PLS models in subhealth recognition was 89.47%, and increased to 92.10% after stepwise regression for variables. CONCLUSION: PLS has certain reference value in establishing subhealth discrimination models. It can also play an important part in item selection of the scale.

Fluorescence study on the interaction of human serum albumin with bromsulphalein.

The binding of bromsulphalein (BSP) with human serum albumin was investigated at different temperatures, 298 and 308 K, by the fluorescence spectroscopy at pH 7.24. The binding constant was determined by Stern-Volmer equation based on the quenching of the fluorescence HSA in the presence of bromsulphalein. The effect of various metal ions on the binding constants of BSP with HSA was investigated. The thermodynamic parameters were calculated according to the dependence of enthalpy change on the temperature as follows: DeltaH and DeltaS possess small negative (9.3 kJ mol(-1)) and positive values (22.3 J K(-l)mol(-l)), respectively. The experimental results revealed that BSP has a strong ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. The binding constants between BSP to HSA were remarkable and independent on temperature. The binding constants between HSA and BSP decreased in the presence of various ions, commonly decreased by 30-55%. The hydrophobic force played a major role in the interaction of BSP with HSA. All these experimental results and theoretical data clarified that BSP could bind to HSA and be effectively transported and eliminated in body, which could be a useful guideline for further drug design.