Synthesis and in vitro antibacterial activities of 7-(4-alkoxyimino-3-hydroxypiperidin- l-yl)quinolone derivatives

A series of novel 7-(4-alkoxyimino-3-hydroxypiperidin-l-yl)quinolone derivatives were designed, synthesized and evaluated for in vitro antibacterial activities. Compounds 8f, 8g, 8i and 8j with the potencies similar to or better than those of levofloxacin and IMB against Staphylococcus aureus and Staphylococcus epidermidis, worth further investigation.     

短链氯化石蜡分析方法

短链氯化石蜡作为一类新型持久性有机污染物已经引起全球的关注,我国是氯化石蜡第一大生产国,但对其研究还处于起步阶段。氯化石蜡组成特别复杂,其定量分析面临巨大的挑战,已成为对氯化石蜡环境存在现状、降解途径以及毒性等进一步研究的瓶颈问题。本文从环境样品的制备、净化、仪器分析以及质量保证4个方面对国际上短链氯化石蜡分析方法的研究进行了评述,针对短链氯化石蜡的分析方法同样适用于中链氯化石蜡。     

Towards the development of a portable sensor based on a molecularly imprinted membrane for the rapid determination of salbutamol in pig urine

A new type of conductometric probe based on a molecularly imprinted membrane (MIM) for the detection of salbutamol has been designed and fabricated. The probe consists of two parallel screen-printed electrodes (SPE). One of the SPEs was coated with a molecularly imprinted membrane using salbutamol as the template, and the other was modified with a non-molecularly imprinted membrane (N-MIM). Measurements of salbutamol were conducted after the conductometric probe had been connected to a commercial portable conductometer. Multi-sample or successive detections could be easily accomplished by replacing the one-off SPE coated with the salbutamol molecularly imprinted membrane with a new one. The conductometric response of the sensor to the concentration of salbutamol displayed a linear correlation over a range from 50 to 280 nM, with a detection limit of 13.5 nM. The recoveries reached 92.1-98.3% based on pig urine samples. In addition, the sensor based on this new type of probe demonstrated high sensitivity and selectivity for salbutamol.     

Nonlinear optical properties of carbon nitride nanotubes

The second order polarizabilities (β) of the C(3)N(4) NT systems were investigated in this study. The β values of end groups substituted C(3)N(4) NTs were calculated to find their most favorable paradigm for nonlinear optical design. It was found that their electric dipole transitions are only allowed along the tube axis direction and the position of terminal groups has a great effect on NLO properties of substituted C(3)N(4) NTs. The obtained results provide us details to understand the relation between the structure and nonlinear optical properties. The results indicate that the second-order polarizabilities originate from charge transfer from a donor (-NH(2)) to an acceptor (-O(2)N) and the electron density redistribution in heptazine units. We employ a one-dimensional two-state model to analyze the nature of the second-order polarizabilities of studied materials. The frequency-dependent second-order polarizabilities were also calculated. The second-order polarizability of the O(2)N-C(3)N(4)-NH(2) NT is 2.51 × 10(-27) esu when the input photon energy is 2.232 eV, which is much larger (about two orders of magnitude) than static second-order polarizability (2.54 × 10(-29)).     

Synthesis of a 3-deoxy-D-manno-octulosonic acid (KDO) building block from D-glucose via fermentation

Herein we report the first synthesis of a 3-deoxy-D-manno-octulosonic acid (KDO) building block starting from glucose through pathway engineering of Escherichia coli and subsequent chemical modifications to provide an alternative method to produce KDO, found in plant and bacterial oligosaccharides.     

Preparation of a MWCNTs/ZnIn2S4 composite and its enhanced photocatalytic hydrogen production under visible-light irradiation

Multiwalled carbon nanotubes (MWCNTs) and ZnIn(2)S(4) composites were prepared by a facile hydrothermal method, which was used for hydrogen production under visible-light (λ≥ 420 nm) irradiation. The obtained MWCNTs/ZnIn(2)S(4) composites were characterized by X-ray diffraction (XRD), thermogravimetric and differential scanning calorimetry analyses (TG-DSC), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance absorption spectra (DRS), Fourier transform IR spectroscopy (FTIR) and Photoluminescence spectra (PL). It was found that the MWCNTs were embedded into the interior of floriated ZnIn(2)S(4) microspheres. The effects of the composite ratio in the MWCNTs/ZnIn(2)S(4) on the photocatalytic activity for hydrogen production were investigated. The results show that the 3 wt% MWCNTs/ZnIn(2)S(4) composite reaches its maximum photocatalytic hydrogen production efficiency with an apparent quantum efficiency as high as 23.3% under 420 nm light irradiation. The significantly enhanced photoactivity for the present composite originates from the synergetic effect of its component intrinsic properties. A possible mechanism of the MWCNTs/ZnIn(2)S(4) composite as a photocatalyst for H(2) evolution was proposed.     

Elucidation of steroid glycosides in Anemarrhena asphodeloides extract by means of comprehensive two-dimensional reversed-phase/polyamine chromatography with mass spectrometric detection

In the work presented here, a novel approach to comprehensive two-dimensional liquid chromatography is evaluated. Reversed-phase liquid chromatography was employed for the first-dimension separation and polyamine chromatography was chosen for the second-dimension separation mode. The two dimensions are highly orthogonal and the separation efficacy of the developed octadecylsilica × polyamine was tested by separating an extract from Anemarrhena asphodeloides. The steroid glycosides identified by comprehensive two-dimensional liquid chromatography in this experiment were compared to those obtained for monodimensional liquid chromatography. The comprehensive two-dimensional liquid chromatography system, thanks to the complementary separation selectivity and enhanced peak capacity provided by the two columns, allowed to distribute five compounds of low amounts otherwise unachievable by monodimensional liquid chromatography. In addition, four steroid isomers with similar fragmentation characteristics in MS/MS spectra, were newly separated based on their different chemical structures.     

Determination of hyperoside and isoquercitrin in rat plasma by membrane-protected micro-solid-phase extraction with high-performance liquid chromatography

A novel method, micro‐solid‐phase extraction based on membrane‐protected molecularly imprinted polymer, was developed to extract hyperoside and isoquercitrin in rat plasma. Synthesized hyperoside MIPs were packed in a porous polyether sulfone membrane envelope to perform extraction. The parameters sorbent materials, membrane types, extraction time and desorption conditions were optimized for micro‐solid‐phase extraction. Under the optimal conditions, correlation coefficients, 0.998 and 0.999, were obtained for hyperoside and isoquercitrin, respectively, with the linear range between 1 and 120 μg/mL. The absolute extraction recoveries from 84.5 to 89.3% were found. The method detection limits of hyperoside and isoquercitrin were 0.24 and 0.22 μg/mL, respectively. Compared with traditional methods, solid‐phase extraction, liquid–liquid extraction and protein precipitation, the developed method was simple, highly efficient for extraction, environmentally friendly, and particularly suitable for complex biological samples.     

Mesoporous silica SBA-15 functionalized with phosphonate and amino groups for uranium uptake

Mesoporous silicas have a very attractive ability of sorption and enrichment of metal ions due to their huge surface area and facile functionalization by organic ligands.In this work,phosphonate-amino bifunctionalized mesoporous silica SBA-15(PA-SBA-15) as U(VI) sorbent was fabricated through post-grafting method.The obtained mesoporous silica was characterized by SEM,XRD,NMR and nitrogen sorption/desorption experiments,which revealed the existence of ordered mesoporous structure with uniform pore diameter and large surface area.The adsorptivity of PA-SBA-15 for U(VI) from aqueous solution was investigated using batch sorption technique under different experimental conditions.The preliminary results show that the U(VI) sorption by PA-SBA-15 is very quick with equilibrium time of less than 1 h,and the U(VI) uptake is as large as 373 mg/g at pH 5.5 under 95 ℃.The sorption isotherm has been successfully modeled by the Langmuir isotherm,suggesting a monolayer homogeneous sorption of U(VI) in PA-SBA-15.The sorption is pH-dependent due to the pH-dependent charge of sorbent in the aqueous solution.The thermodynamics research shows that the sorption is a feasible and endothermic process.Based on these results,PA-SBA-15 could be a promising solid phase sorbent for highly-efficient removal of U(VI) ions from waste water and enrichment of U(VI) from a solution at a very low level.     

Genome-scale DNA methylation pattern profiling of human bone marrow mesenchymal stem cells in long-term culture

Human bone marrow mesenchymal stem cells (MSCs) expanded in vitro exhibit not only a tendency to lose their proliferative potential, homing ability and telomere length but also genetic or epigenetic modifications, resulting in senescence. We compared differential methylation patterns of genes and miRNAs between early-passage [passage 5 (P5)] and late-passage (P15) cells and estimated the relationship between senescence and DNA methylation patterns. When we examined hypermethylated genes (methylation peak ≥ 2) at P5 or P15, 2,739 genes, including those related to fructose and mannose metabolism and calcium signaling pathways, and 2,587 genes, including those related to DNA replication, cell cycle and the PPAR signaling pathway, were hypermethylated at P5 and P15, respectively. There was common hypermethylation of 1,205 genes at both P5 and P15. In addition, genes that were hypermethylated at P5 (CPEB1, GMPPA, CDKN1A, TBX2, SMAD9 and MCM2) showed lower mRNA expression than did those hypermethylated at P15, whereas genes that were hypermethylated at P15 (MAML2, FEN1 and CDK4) showed lower mRNA expression than did those that were hypermethylated at P5, demonstrating that hypermethylation at DNA promoter regions inhibited gene expression and that hypomethylation increased gene expression. In the case of hypermethylation on miRNA, 27 miRNAs were hypermethylated at P5, whereas 44 miRNAs were hypermethylated at P15. These results show that hypermethylation increases at genes related to DNA replication, cell cycle and adipogenic differentiation due to long-term culture, which may in part affect MSC senescence.