稳定同位素表征有机物甲烷化代谢动力学

有机物甲烷化可通过乙酸发酵型、氢营养型和甲基营养型3种途径进行,确定各个途径对甲烷生成的贡献率是其动力学研究的基本问题,稳定同位素示踪技术是研究生态体系甲烷主导生成途径的创新方法.本文综述了稳定同位素技术表征甲烷生成途径的方法进展及影响测试解析结果的因素.产甲烷过程中的稳定同位素分馏效应是影响测试结果解析的关键,甲烷菌类型、生长阶段、底物丰度、温度等是其主要影响因素;对典型产甲烷生态体系进行控制实验,积累分馏效应数据及联合应用微生态分子生物学表征方法,是提高稳定同位素技术对甲烷生成途径区分水平的可行方法.联合应用稳定同位素表征技术和微生态原位表征方法,对高浓度有机酸胁迫条件下的生物质类有机物厌氧发酵甲烷化途径的研究结果表明,面临高浓度有机酸迅速累积的环境,中温发酵条件下,优势菌种为甲烷八叠球菌,依时间次序,通过乙酸发酵和氢营养型途径利用累积的有机酸产生甲烷;而在高温条件下,有机酸则通过乙酸氧化和氢营养型甲烷化途径的串联反应被降解.运用稳定同位素表征技术揭示甲烷生成途径可为针对性的微生态调控提供依据.     

DNA combining and photocleaving properties of photosensitizer-encapsulated silica nanoparticles

Abstract  

Based on theoretical predictions, water-soluble silica nanoparticle encapsulated hypocrellin A (HA) was prepared, and its photosensitization activity was evaluated. The encapsulated HA showed not only very good water solubility, but also much stronger singlet oxygen generation ability than free HA. Investigations on binding interactions with DNA showed promising results as well. These findings suggest that HA carrier can exert photodynamic action via photosensitization.     

Sarcoglycosides A – C,New O‐Glycosylglycerol Derivatives from the South China Sea Soft Coral Sarcophyton infundibuliforme

Chemical examination of the soft coral Sarcophyton infundibuliforme collected from the South China Sea resulted in the isolation of the three new O‐glycosylglycerol derivatives sarcoglycosides A–C ( 1 – 3 ), together with two known compounds, chimyl alcohol ( 4 ) and hexadecanol ( 5 ). Their structures were elucidated by combined spectral and chemical methods. All the compounds showed moderate toxicity to brine shrimps Artemia salina.     

Determination of 76 pharmaceutical drugs by liquid chromatography–tandem mass spectrometry in slaughterhouse wastewater

A multi-residue method for the analysis of 76 pharmaceutical agents of nine classes of drugs (tetracyclines, macrolides, fluoroquinolones, β-agonists, β-blockers, diuretics, sedatives, sulfonamides and chloramphenicol) in slaughterhouse wastewater and a receiving river is presented. After simultaneous extraction with an Oasis HLB solid-phase extraction (SPE) cartridge and further purification using an amino SPE cartridge, analytes were detected by liquid chromatography–electrospray ionization-tandem mass spectrometry in positive or negative ion mode. Standard addition was used for quantification to overcome unavoidable matrix effects during ESI-MS analysis. Recoveries for most analytes based on matrix-matched calibration in different test matrices were >60%. The method quantification limits of 76 pharmaceuticals were in the range 0.2–30 ng/L. Nineteen compounds of 76 drugs were found in raw and treated slaughterhouse wastewater from four main slaughterhouses in Beijing. Sulfanamides (sulfanilamide, sulfameter), fluoroquenones (ofloxacin, pefloxacin, norfloxacin, ciprofloxacin, enrofloxacin), tetracyclines (tetracycline, oxytetracycline) and macrolides (kitasamycin, tylosin, erythromycin) were most frequently detected, with the highest levels up to ∼3 μg/L in slaughterhouse wastewater and ∼1 μg/L in treated wastewater. Illicit drugs for animal feeding such as clenbuterol and diazepam were commonly detected in slaughterhouse wastewater. These analytes were also observed in a river receiving slaughterhouse wastewater, with a highest level of up to 0.2 μg/L.     

Modeling of radionickel sorption on MX-80 bentonite as a function of pH and ionic strength

MX-80 bentonite was detected using acid-based titration, XRD and FTIR in detail. The sorption behavior of 63Ni(Ⅱ) from aqueous solution to MX-80 bentonite was investigated as a function of solid content, ionic strength and pH by using batch technique. The experimental data of 63Ni(Ⅱ) sorption on MX-80 bentonite was obtained using the diffuse layer model (DLM) with the aid of FITEQL 3.1 program. The results indicated that the sorption of 63Ni(Ⅱ) on MX-80 bentonite was mainly dominated by surface complexation...     

Oscore: a combined score to reduce false negative rates for peptide identification in tandem mass spectrometry analysis

Tandem mass spectrometry (MS/MS) has been widely used in proteomics studies. Multiple algorithms have been developed for assessing matches between MS/MS spectra and peptide sequences in databases. However, it is still a challenge to reduce false negative rates without compromising the high confidence of peptide identification. In this study, we developed the score, Oscore, by logistic regression using SEQUEST and AMASS variables to identify fully tryptic peptides. Since these variables showed complicated association with each other, combining them together rather than applying them to a threshold model improved the classification of correct and incorrect peptide identifications. Oscore achieved both a lower false negative rate and a lower false positive rate than PeptideProphet on datasets from 18 known protein mixtures and several proteome-scale samples of different complexity, database size and separation methods. By a three-way comparison among Oscore, PeptideProphet and another logistic regression model which made use of PeptideProphet's variables, the main contributor for the improvement made by Oscore is discussed.     

Tunability of anion binding strength based on acyl-thiourea receptors containing isatin group

Some acyl-thiourea derivatives containing isatin group were synthesized and their interactions with anions were investigated using UV–vis spectroscopy and ¹H NMR titrations in DMSO and DMSO-d₆, respectively. These compounds have a same molecular framework, functionalising with different groups lead to different anion binding strength of these receptors. Receptor 1 showed a higher binding affinity for AcO⁻ than for F⁻, due to the cooperative multiple hydrogen bond interactions of AcO⁻ with the acyl-thiourea group and N–H group in the indole unit of receptor 1. Displacing the N–H proton in the indole unit with –CH₃ group, receptor 2 showed no obviously discriminative responses for F⁻, AcO⁻ and H₂PO₄⁻ due to lack of such additional binding. In the case of receptor 3, which was functionalised with strong electron-withdrawing group, it showed selectively chromogenic response for F⁻ based on double deprotonation of the receptor in DMSO, whereas AcO⁻ and H₂PO₄⁻ induced single deprotonation only.     

Methane-fueled SOFC with traditional nickel-based anode by applying Ni/Al2O3 as a dual-functional layer

Novel γ-Al₂O₃ supported nickel (Ni/Al₂O₃) catalyst was developed as a functional layer for Ni–ScSZ cermet anode operating on methane fuel. Catalytic tests demonstrated Ni/Al₂O₃ had high and comparable activity to Ru–CeO₂ and much higher activity than the Ni–ScSZ cermet anode for partial oxidation, steam and CO₂ reforming of methane to syngas between 750 and 850 °C. By adopting Ni/Al₂O₃ as a catalyst layer, the fuel cell demonstrated a peak power density of 382 mW cm^?2 at 850 °C, more than two times that without the catalyst layer. The Ni/Al₂O₃ also functioned as a diffusion barrier layer to reduce the methane concentration within the anode; consequently, the operation stability was also greatly improved without coke deposition.     

A potential energy surface survey of OB6: global minima and isomerization stability

In light of the very recent significant discrepancies on the global isomer of the sept-atomic molecule OB₆, we performed a detailed potential energy surface survey of OB₆ covering various isomeric forms. We showed that at the CCSD(T)/6-311+G(2df)//B3LYP/6-311+G(d) level, the planar knife-like isomer 01 with a –BO moiety has the lowest energy, followed by the planar belt-like isomer 02 at 22.6 kcal/mol. Another isomer 05 at 33.1 kcal/mol can be viewed as the direct O-adduct of the pentagonal pyramid B₆. Kinetically, the three isomers 01, 02 and 05 all have considerable barriers (19–29 kcal/mol) (obtained at B3LYP/6-311+G(d) level) against isomerization. However, other isomers either have much higher energy or possess much smaller conversion barriers and are thus of little likeliness for isolation. Moreover, though being isoelectronic to the well-known CB ₆ ^2? molecule, OB₆ does not have any kinetically stabilized wheel-like isomers with O or B centers. The three OB₆ isomers 01, 02 and 05 await future laboratory studies. The detailed results reported in this paper are expected to provide useful information for understanding the growing process of boron oxides, O-doping and oxidation mechanism of boron clusters.     

The Antimony‐Based Type I Clathrate Compounds Cs8Cd18Sb28 and Cs8Zn18Sb28

In phase : The title compounds lie in a new region of phase space for such a structure, and have stoichiometries in accord with a classical Zintl phase formulation. The small semiconductor gaps indicated by DFT calculations are also supported by their diamagnetic susceptibilities.