色谱法在三氯半乳蔗糖合成中的应用

采用薄层色谱和柱色谱法,选择优化展开体系,有效地分析了三氯半乳蔗糖中间体2,3,6,3′,4′-五氧乙酰蔗糖混合物,并证实该混合物中杂质为三苯甲醇,为三氯半乳蔗糖的合成研究取得了重要发现。     

龙门山地区水系沉积物中铀含量分布特征

铀元素是具有毒性和放射性的锕系元素之一,对区域环境和人体健康具有极大的危害,开展铀元素污染评价具有重要的现实意义。以龙门山地区主要水系为主要研究对象,采集了大量的水系沉积物样品,对该地区的铀元素分布特征进行了研究。研究表明,大渡河水系沉积物中铀平均质量分数为5.50 mg/kg,绵远河水系沉积物中的铀平均质量分数为3.07 mg/kg,其余河流水系沉积物中铀含量均较低。通过龙门山地区水系沉积物中铀元素分布特征与龙门山地区矿产分布对比发现,煤矿、磷矿开发区是水系主要铀元素来源。     

高效液相色谱串联质谱法测定含藻水氯化消毒后7种亚硝胺物质

采用液相色谱串联质谱法(LC/MS/MS)测定含藻水氯消毒产生7种亚硝胺类(NAms)消毒副产物(NDMA,NMEA,NDEA,NDPA,NDBA,NPyr,NPip).方法检出限分别为5.0,14,8.6,3.6,2.9,6.3和4.9 ng/L,相关系数r＞0.999.除NDBA回收率(60％)较低外,其余6种亚硝胺回收率均在80％～120％之间,相对标准偏差为1.4％～12.6％.分别以藻原液和消毒后藻液配制基质标准曲线,采用其与纯水标准曲线斜率之比评估基质效应.藻原液的基质效应为0.79 ～0.94,藻液消毒后NDMA基质效应为0.36,其他亚硝胺为0.63～0.96.应用此方法检测了自来水、富营养江河水、景观水及藻类悬浮液氯消毒后的亚硝胺含量.     

Langmuir-Blodgett film of p-tert-butylthiacalix[4]arene modified glassy carbon electrode as voltammetric sensor for the determination of Hg(II)

The π-A isotherms and UV-vis spectra of the transferred films suggested that the monolayer of p-tert-butylthiacalix[4]arene can coordinate with Hg²⁺ at the air-water surface. From these observations, a glassy carbon electrode coated with Langmuir-Blodgett film of p-tert-butylthiacalix[4] arene as a new voltammetric sensor is designed for the determination of trace amounts of Hg²⁺. Compared with bare glassy carbon electrode and modified glassy carbon electrode using direct coating method, the Langmuir-Blodgett film-modified electrode can greatly improve the measuring sensitivity of Hg²⁺. Under the selected conditions, the Langmuir-Blodgett film-modified electrode in 0.1 mol L⁻¹ H₂SO₄ + 0.01 mol L⁻¹ KCl solution shows a linear voltammetric response for Hg²⁺ in the range of 5.0 × 10⁻¹⁰ to 1.5 × 10⁻⁷ mol L⁻¹, with a detection limit of 2.0 × 10⁻¹⁰ mol L⁻¹. The proposed method was also applied to determine Hg²⁺ in water samples (tap, lake and river water). In addition, the fabricated electrode exhibited a distinct advantage of simple preparation, non-toxicity, good reproducibility and good stability.     

DNA binding and photocleavage properties of two mixed-ligand oxovanadium complexes

An oxovanadium complex [VO(satsc)(bipy)] (1) (satsc = salicylaldehyde thiosemicarbazone, bipy = 2,2′-bipyridine) and its dibromo derivative [VO(3,5-dibrsatsc)(bipy)] (2) (3,5-dibrsatsc = 3,5-dibromosalicylaldehyde thiosemicarbazone) have been synthesized and characterized by elemental analysis, IR, ES-MS and ¹H NMR. The interaction of these two complexes with calf-thymus DNA (CT-DNA) was studied using UV/Vis, fluorescence spectroscopic titration, viscosity measurements and thermal denaturation. The results suggest that complexes 1 and 2 interact with CT-DNA by intercalative modes. The DNA-binding affinity of complex 1 is larger than that of complex 2. In addition, their photocleavage reactions with pBR322 supercoiled plasmid DNA were investigated by gel electrophoresis experiments. Both complexes exhibit significant DNA cleavage activity, and complex 1 showed greater cleaving efficiency than complex 2.     

Electrodeposition of PtCo alloy nanoparticles on inclusion complex film of functionalized cyclodextrin–ionic liquid and their application in glucose sensing

Platinum–cobalt (PtCo) alloy nanoparticles (NPs) are successfully fabricated by ultrasonic-electrodeposition method, using an inclusion complex (IC) film of functionalized cyclodextrin (CD)–ionic liquid (IL) as support. The morphology and composition of the PtCo alloy NPs are characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction, respectively. It is found that they are well-dispersed on the CD–IL surface and exhibit many unique features. The resulting modified glassy carbon electrode shows excellent catalytic activity for glucose oxidation. Under the physiological condition, the oxidation current of glucose is linear to its concentration up to 20 mM with sensitivity of 13.7 μA mM^?1 cm^?2. In addition, the interference from the oxidation of ascorbic acid and uric acid could be effectively avoided. Therefore, it is promising as a nonenzymatic glucose sensor.     

Temperature-responsive amperometric H<Subscript>2</Subscript>O<Subscript>2</Subscript> biosensor using a composite film consisting of poly(N-isopropylacrylamide)-b-poly (2-acrylamidoethyl benzoate), graphene oxide and hemoglobin

A temperature-responsive biosensing film consisting of the temperature-responsive block co-polymer poly (N-isopropylacrylamide)-b-poly(2-acrylamidoethyl benzoate) (referred to as PNIPAM-b-PAAE), graphene oxide (GO), and hemoglobin (Hb) was fabricated and used to modify a glassy carbon electrode (GCE). The film provides a favorable micro-environment for Hb to facilitate the electron transfer to the GCE. Hb at PNIPAM-b-PAAE/GO/Hb (PGH) film exhibits a couple of well-defined redox peaks with a formal potential of ?0.371 V (vs. SCE) and displays intrinsic electro-catalytic activity toward H₂O₂. The sensing film also shows temperature-tunable catalytic activity toward H₂O₂ that can be stimulated by temperature. Large peak currents can be seen in amperometry at 0.4 V (vs. SCE) in pH 7.0 phosphate buffer only if the temperature is above the lower critical solution temperature (LCST) of 32 °C. The response of the modified GCE is linear in the 0.1 to 3.7 μmol L^?1 concentration range if operated at above 32 °C, but in the 0.2 to 3.7 μmol L^?1 concentration range at below 30 °C. This behavior is attributed to the temperature-dependent phase transition of PNIPAM-b-PAAE and cooperative effect of GO. The strategy presented here in our perception meets the requirements of switchable sensors for use in bioscience and biotechnology.

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Graphical abstract A temperature-responsive biosensing film consisting of temperature-responsive polymer, graphene oxide and hemoglobin has been fabricated. This film displays favorable electrochemical property and good electro-catalytic activity toward H₂O₂. It also exhibits catalytic activity change upon temperature stimuli.

     

Extensional rheology of cellulose/NaOH/urea/H<Subscript>2</Subscript>O solutions

The extensional flow behaviors of cellulose/NaOH/urea/H₂O solution were investigated by using capillary breakup extensional rheometry (CaBER). The effects of temperature, storage time and cellulose concentrations on both the storage modulus G′ and the loss modulus G″ were also analyzed. For 2 wt% cellulose solution, the G′, G″ and filament lifetime remained unchanged after long storage time. While, for 4 wt% cellulose solution, physical gels could form at either higher temperature or for longer storage time, and the filament lifetime, the relaxation time (λ _e ) and the initial extensional viscosity (η _e0) first increased and then decreased with increase of the storage time. The transition points of the filament lifetime shifted to lower storage time with the increase of the temperature. The η _e0 is proportional to λ _e . The results presented suggest that the extensional properties of the cellulose/NaOH/urea/H₂O solution first increase and then decrease during the gelation process, and the spinning time, which decreases linearly with the increase in the storage temperature, must be controlled below the time that η _e0 starts to decrease.     

Graphene quantum dots with Zn2+ and Ni2+ conjugates can cleave supercoiled DNA

Graphene quantum dots (GQDs), inheriting the superb property of graphene oxide, possess smaller lateral size and high biocompatibility, thus having potential in biomedical applications. We previously discovered that GQDs, combining with Cu²⁺ ions, could cleave DNA primarily through an oxidative pathway; yet, oxidative DNA cleavage is not practically preferred in biology. In this work, we explore the DNA cleavage ability of GQDs with Zn²⁺ and Ni²⁺. Zn²⁺ and Ni²⁺ alone are incapable of cleaving supercoiled DNA, but when combining with the GQDs, Zn²⁺ and Ni²⁺ exhibit DNA cleavage activity. However, the activity of these two systems is much lower than that of GQDs/Cu²⁺, and GQDs/Ni²⁺ is less active than GQDs/Zn²⁺. The functional mechanism of GQDs/Ni²⁺ and GQDs/Zn²⁺ is different from that of GQDs/Cu²⁺. The GQDs play a key role in the two systems; the redox inactive Zn²⁺ and Ni²⁺ ions assist to generate the oxidative species that eventually lead to the DNA cleavage. The current results together with our previous result indicate that GQDs together with metal ions can cleave supercoiled DNA, and their cleavage activities depend on the properties of metal ions: for redox active metal ions, metal ions play key roles, for redox inactive metal ions, GQDs are dominant.     

Alcohol‐Induced C−N Bond Cleavage of Cyclometalated N‐Heterocyclic Carbene Ligands with a Methylene‐Linked Pendant Imidazolium Ring

Reaction of the pentamethylcyclopentadienyl rhodium iodide dimer [Cp*RhI₂]₂ with 1,1′‐diphenyl‐3,3′‐methylenediimidazolium diiodide in non‐alcohol solvents, in the presence of base, led to the formation of bis‐carbene complex [Cp*Rh(bis‐NHC)I]I (bis‐NHC=1,1′‐diphenyl‐4,4′‐methylenediimidazoline‐5,5′‐diylidene). In contrast, when employing alcohols as the solvent in the same reaction, cleavage of a methylene C?N bond is observed, affording ether‐functionalized (cyclometalated) carbene ligands coordinated to the metal center and the concomitant formation of complexes with a coordinated imidazole ligand. Studies employing other 1,1′‐diimidazolium salts indicate that the cyclometalation step is a prerequisite for the activation/scission of the C?N bond and, based on additional experimental data, a S_N2 mechanism for the reaction is tentatively proposed.