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271.
Mariano Licciardi 《European Polymer Journal》2006,42(4):823-834
The non-viral gene vector properties of a protein-like polymer, the α,β-poly(N-2-hydroxyethyl)-d,l-aspartamide (PHEA) were investigated after its derivatization with 3-(carboxypropyl)trimethyl-ammonium chloride (CPTA) as molecule bearing cationic groups, in order to obtain stable polycations able to condense DNA. PHEA was firstly functionalized with hydrazide pendant groups by reaction with hydrazine monohydrate (HYD), obtaining the polyhydrazide α,β-poly(N-2-hydroxyethyl/carbazate)-d,l-aspartamide (PHEA-HYD). In this paper we reported that polymer functionalization degree can be easily modulated by varying reaction conditions, so allowing us to produce two PHEA derivatives at different molar percentage of hydrazide groups. Subsequently, condensation reaction of PHEA-HYD copolymers with CPTA yielded α,β-poly(N-2-hydroxyethyl)-N-carbazate[N′-(3-trimethylammonium chloride)propylhydrazide]-d,l-aspartamide (PHEA-HYD-CPTA) polycation derivatives. In vitro studies were carried out to evaluate polycations ability to complex DNA and to protect it from nuclease degradation. Obtained results demonstrated the good efficiency of our new PHEA-polycations derivatives, PHEA-HYD-CPTA, to complex and condense genomic material even at very low polycation/DNA weight ratio. 相似文献
272.
露天转地下最佳开采模式 总被引:2,自引:0,他引:2
建立露天转地下开采模式综合评判模型,运用层次分析法和模糊数学的基本原理对多种开采模式进行评判优选.评判优选过程中,综合考虑影响露天转地下开采模式的动态、静态、定量、非定量指标,如技术、经济指标及边坡稳定程度等:将待选择方案指标转换成隶属度矩阵,通过层次分析法得到各因素权重向量;从而建立模糊综合评判模型,利用模糊数学原理计算出各方案基于影响因素的综合优越度.以石人沟铁矿为例,4种开采模式的优越度分别为45.82%,84.32%,89.88%,80.75%,从而确定第3种方案最优. 相似文献
273.
One-step in situ microwave-assisted headspace solid-phase microextraction (MA-HS-SPME) followed by gas chromatography–mass spectrometry (GC–MS) analysis is presented as a fast and solvent-free technique to determine synthetic polycyclic musks in sewage sludge and sediment samples. Six synthetic polycyclic musks (galaxolide (HHCB), tonalide (AHTN), celestolide (ADBI), traseolide (ATII), cashmeran (DPMI) and phantolide (AHMI)) were selected in the method development and validation. The effects of extraction parameters for the quantitative extraction of these analytes by one-step MA-HS-SPME were systematically investigated. The dewatered solid sample mixed with 20-mL deionized water (containing 3 g of NaCl in a 40-mL sample-vial) was efficiently extracted by a polydimethylsiloxane-divinylbenzene (PDMS-DVB) fiber placed in the headspace when the extraction slurry was microwave irradiated at 80 W for 5 min. The limits of detection (LODs) ranged from 0.04 to 0.1 ng/g, and the limits of quantification (LOQs) ranged from 0.1 to 0.3 ng/g (fresh weight). A preliminary analysis of sludge and sediment samples revealed that HHCB and AHTN were the two most commonly detected synthetic polycyclic musks; using a standard addition method, their total concentrations were determined to range from 0.3 to 10.9 ng/g (fresh weight) with relative standard deviation (RSD) ranging from 4% to 10%. 相似文献
274.
Gestrinone is a synthetic steroid hormone with anti-estrogenic and anti-progesterone properties. It is used to treat endometriosis, shrink uterine fibroids and reduce menorrhagia; besides, it has been investigated for use as contraceptive. Also, due to its anabolic effects, it has been included in the banned list of performance enhanced drugs in sport. Polyclonal antibodies raised against bovine serum albumin coupled to gestrinone 3-carboxymethyloxime (3OCMO-G) were used to develop two highly sensitive and specific enzyme-linked immunosorbent assays for gestrinone. One of them, based on direct format, shows a detection limit (LD) of 0.09 ± 0.03 ng L−1. The second assay, hapten-protein coating format, can detect until (LD) 0.14 ± 0.05 ng L−1. Both immunoassays were also highly specific, showing negligible or no cross-reactivity to other anabolic steroids. The developed ELISAs detected lower amounts of gestrinone than those determined by the reference chromatographic HPLC/MS/MS methods. The direct format was applied to quantify this steroid in spiked human urine without sample pre-treatment, with recovery values between 76 and 122%. 相似文献
275.
Kentaro Yaji 《Tetrahedron letters》2010,51(41):5469-942
A synthetic study of the Stemona alkaloid stemonamide is described. The FeCl3-promoted fast Nazarov reaction of β-alkoxy divinyl ketones in the presence of t-BuOH afforded an α-methylene cyclopentenone, which was subsequently subjected to the Rh-catalyzed C-H amination to provide a fully appropriately substituted α-methylene cyclopentenone as the core skeleton of stemonamide. 相似文献
276.
Cristiana Boi Valentina Busini Matteo Salvalaglio Carlo Cavallotti Giulio C. Sarti 《Journal of chromatography. A》2009,1216(50):8687-8696
Affinity chromatography with Protein A beads has become the conventional unit operation for the primary capture of monoclonal antibodies. However, Protein A activated supports are expensive and ligand leakage is an issue to be considered. In addition, the limited production capabilities of the chromatographic process drive the research towards feasible alternatives. The use of synthetic ligands as Protein A substitutes has been considered in this work. Synthetic ligands, that mimic the interaction between Protein A and the constant fragment (Fc) of immunoglobulins, have been immobilized on cellulosic membrane supports. The resulting affinity membranes have been experimentally characterized with pure immunoglobulin G (IgG). The effects of the membrane support and of the spacer arm on the ligand–ligate interaction have been studied in detail. Experimental data have been compared with molecular dynamic simulations with the aim of better understanding the interaction mechanisms. Molecular dynamic simulations were performed in explicit water, modelling the membrane as a matrix of overlapped glucopyranose units. Electrostatic charges of the ligand and spacer were calculated through ab initio methods to complete the force field used to model the membrane. The simulations enabled to elucidate how the interactions of surface, spacer and ligand with IgG, contribute to the formation of the bond between protein and affinity membrane. 相似文献
277.
M. C. Bastos L. F. A. Proença M. M. M. Neto I. T. E. Fonseca 《Journal of Solid State Electrochemistry》2008,12(2):121-131
This paper reports an electrochemical study on the corrosion of brass in deoxygenated nonbuffered and buffered natural and
artificial seawater solutions under anaerobic conditions. Cyclic voltammograms of brass and copper in natural seawater (NSW)
and artificial seawater (ASW) were obtained in the passive and transpassive potential regions. The corrosion resistance of
brass in natural and artificial seawater was evaluated, and open-circuit potentials were recorded over exposure period of
1 week. Brass samples from 3-month exposures in deoxygenated nonbuffered ASW and NSW, under open-circuit potential, have been
imaged by scanning electron microscopy, and the elemental composition of the corrosion products was obtained by energy dispersive
spectrometry analysis. It has been concluded that, under anaerobic conditions, the aggressivity of NSW is higher, with brass
being less resistant to corrosion than copper, and that buffer contributes to reduce the aggressivity of both media. 相似文献
278.
279.
康德在《判断力批判》中把"审美无利害"作为审美最基本也是最重要的特点,从而把审美愉悦与其它两种--由感官引起的快适和对善的追求所引起的愉悦区别开来.但这种无目的的合目的性的审美最终还是借助于一个美的理想,而这一理想又在一定程度上借助了道德性. 相似文献
280.
针对复杂背景条件下声目标的自动识别问题,设计了一种基于模糊综合评判的声目标识别系统,该系统在对典型战场声目标特征进行充分提取与选择的基础上,建立反映目标类属特征的隶属函数库,采用先进的模糊综合评判技术实现对目标的可靠识别,对特征提取与选择、隶属函数确定、模糊评判、原理样机实现等关键问题进行了详细的讨论。实测检验表明,该系统对战场声目标具有良好的识别分类效果。 相似文献