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91.
Guzmán E Cavallo JA Chuliá-Jordán R Gómez C Strumia MC Ortega F Rubio RG 《Langmuir : the ACS journal of surfaces and colloids》2011,27(11):6836-6845
Multilayers of poly(acrylic acid), PAA, and chitosan, CHI, have been built by the layer-by-layer (LbL) method from aqueous solutions at different pH values and analyzed by the dissipative quartz crystal microbalance (D-QCM) and ellipsometry. The results showed that under all of the assembly conditions considered the growth of the films is nonlinear. The thickness of the PAA layers increases as the pH of the assembling solutions decreases, whereas the adsorption of CHI is almost unaffected by the pH conditions. The comparison of the thickness obtained by D-QCM and by ellipsometry has allowed us to calculate the water content of the films, showing that the multilayers are highly hydrated, with an average water content higher than 20%. The analysis of D-QCM data has provided high-frequency values of the complex shear modulus that are in the megapascal range and shows a transition from mainly viscous to mainly elastic behavior for the added PAA layers, depending on the pH. The monomer surface density in each layer (obtained from the combination of ellipsometry and differential refractive index measurements) indicated that the monomer density depends on the assembly conditions. It was found that the adsorption kinetics is a bimodal process, with characteristic times that depend on the number and nature of the layers. Finally, the possibility of using of these multilayers as a drug storage and delivery system has been evaluated. 相似文献
92.
Diego AlvesMaraisa Sachini Raquel G. JacobEder J. Lenardão Maria E. ContreiraLucielli Savegnago Gelson Perin 《Tetrahedron letters》2011,52(1):133-135
PEG-400 and glycerol were successfully used as recyclable solvents for the synthesis of several organylthioenynes in good to excellent yields and high selectivity using solid supported catalyst (KF/Al2O3). This easy, general and improved method furnishes the corresponding alkenyl sulfides preferentially with Z configuration. The catalytic system and the glycerol or PEG-400 can be reused up to three times without previous treatment with comparable activity. 相似文献
93.
Giménez E Ramos-Hernan R Benavente F Barbosa J Sanz-Nebot V 《Rapid communications in mass spectrometry : RCM》2011,25(16):2307-2316
Capillary electrophoresis coupled to orthogonal accelerated time-of-flight mass spectrometry (CE/TOFMS) was used for the analysis of O- and N-glycopeptides of recombinant human erythropoietin (rhEPO). O(126) and N(83) with a tetraantennary complex type glycan (N(83)-4Ant) were selected as glycopeptide models to develop an optimum CE/TOFMS methodology capable of detecting and characterizing the wide variety of glycopeptides present in the glycoprotein digest. Glycopeptide adsorption in the inner surface of the fused-silica capillary was prevented after using a capillary conditioning of 1 M HAc between runs. On the other hand, different acidic conditions in the sheath liquid (SL) and in the background electrolyte (BGE) were tested with the aim of studying their influence in glycopeptide fragmentation. Finally, the fragmentor voltage value of the TOF-MS instrument was optimized to avoid the involuntary fragmentation of the native glycopeptides. Hence, the established method may be regarded as an excellent starting point to obtain reliable glycopeptide maps of complex glycoproteins such as rhEPO by CE/TOFMS. 相似文献
94.
Gomes AG Azevedo AM Aires-Barros MR Prazeres DM 《Journal of chromatography. A》2011,1218(48):8629-8637
Plasmid DNA (pDNA) is purified directly from alkaline lysis-derived Escherichia coli (E. coli) lysates by phenyl boronate (PB) chromatography. The method explores the ability of PB ligands to bind covalently, but reversibly, to cis-diol-containing impurities like RNA and lipopolysaccharides (LPS), leaving pDNA in solution. In spite of this specificity, cis-diol free species like proteins and genomic DNA (gDNA) are also removed. This is a major advantage since the process is designed to keep the target pDNA from binding. The focus of this paper is on the study of the secondary interactions between the impurities (RNA, gDNA, proteins, LPS) in a pDNA-containing lysate and 3-amino PB controlled pore glass (CPG) matrices. Runs were designed to evaluate the role of adsorption buffer composition, feed type (pH, salt content), CPG matrix and sample pretreatment (RNase A, isopropanol precipitation). Water was chosen as the adsorption buffer over MgCl(2) solutions since it maximised pDNA yield (96.2±4.9%) and protein removal (61.3±3.0%), while providing for a substantial removal of RNA (65.5±3.5%) and gDNA (44.7±14.1%). Although the use of pH 3.5 maximised removal of impurities (~75%), the best compromise between plasmid yield (~96%) and RNA clearance (~60-70%) was obtained for a pH of 5.2. Plasmid yield was maximal (>96%) when the concentration of acetate and potassium ions in the incoming lysate feed were 1.7 M and 1.0 M, respectively. The pre-treatment of lysates with RNase A deteriorated the performance since the resulting oligoribonucleotides lack the cis-diol group at their 3' termini. Overall, the results support the idea that charge transfer interactions between the boron atom at acidic pH and electron donor groups in the aromatic bases of nucleic acids and side residues of proteins are responsible for the non-specific removal of gDNA, RNA and proteins. 相似文献
95.
Using enalapril maleate as a test case, the ability of ambient mass spectrometry, namely, via easy ambient sonic‐spray ionization mass spectrometry (EASI‐MS), to perform direct monitoring of drug degradation has been tested. Two manufacturing processes were investigated (direct compression and wet granulation), and the formation of degradation products was measured via both EASI‐MS and high‐performance liquid chromatography with ultraviolet detection for a total period of 18 months. Both techniques provide comparable results, which indicate that direct analysis by ambient mass spectrometric techniques presents a viable alternative for drug degradation monitoring with superior simplicity, throughput, and reliability (no sample manipulation), and comparable quantitative results. In terms of qualitative monitoring, the full mass spectra with intact species provided by EASI‐MS allow for comprehensive monitoring of known and unknown (or unexpected) degradation products. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
96.
Popularity of new psychoactive substances, known as legal highs or herbal highs, is continuously growing. These products are
typically sold via internet and in so-called head shops. The aim of this study was to identify active ingredients of herbal
highs and to compare their chemical composition. Twenty-nine various products seized by the police in one of the “head shops”
were analysed. Herbal mixtures (0.2 g) were prepared by ultrasonic-assisted extraction with 2.0 ml of ethanol for 2 h. The
extracts were analysed by gas chromatography coupled to mass spectrometry (GC/MS). The main active compounds of the herbal
mixtures were synthetic cannabinoids: JWH-018, JWH-073 and cannabicyclohexanol (CP-47,497-C8-homolog). Their content differed
between the products; some contained only one cannabinoid whereas the others contained two or more. Cluster analysis and principal
component analysis revealed that chemical composition of many products was very similar. The similarity was connected with
their flavour and not the common name. This statement was true for the synthetic cannabinoids, other potential agonists of
cannabinoid receptors (amides of fatty acids) and ingredients of natural origin and confirms that herbal highs are a threat
to human health because the purchaser has no information on their real composition. 相似文献
97.
In this paper we present two new algorithmic variants to compute the Neville elimination, with and without pivoting, which improve data locality and cast most of the computations in terms of high-performance Level 3 BLAS. The experimental evaluation on a state-of-the-art multi-core processor demonstrates that the new blocked algorithms exhibit a much higher degree of concurrency and better cache usage, yielding higher performance while offering numerical accuracy akin to that of the traditional columnwise variant in most cases. 相似文献
98.
Monreal MJ Khan SI Kiplinger JL Diaconescu PL 《Chemical communications (Cambridge, England)》2011,47(32):9119-9121
A new inverted sandwich of a μ-η(6),η(6)-toluene diuranium complex reacted with quinoxaline to form a tetranuclear macrocycle with ferrocene diamide uranium(IV) vertices and reduced quinoxaline edges. 相似文献
99.
Rangel TB Assreuy AM Pires Ade F Carvalho AU Benevides RG Simões Rda C Silva HC Bezerra MJ Nascimento AS Nascimento KS Nagano CS Sampaio AH Delatorre P Rocha BA Fernandes PM Cavada BS 《Molecules (Basel, Switzerland)》2011,16(6):5087-5103
DwL, a lectin extracted from the seeds of Dioclea wilsonii, is a metalloprotein with strong agglutinating activity against rabbit and ABO erythrocytes, inhibited by glucose and mannose. DwL was purified by affinity chromatography on a Sephadex G-50 column and ion exchange chromatography on a HiTrap SP XL column. SDS-PAGE revealed three electrophoretic bands corresponding to the α (25,634 ± 2 Da), β (12,873 ± 2 Da) and γ (12,779 ± 2 Da) chains. Protein sequencing was done by Tandem Mass Spectrometry. The primary sequence featured 237 amino acids and was highly homologous to other reported Diocleinae lectins. A complete X-ray dataset was collected at 2.0 ? for X-Man-complexed DWL crystals produced by the vapor diffusion method. The crystals were orthorhombic and belonged to the space group I222, with the unit-cell parameters a = 59.6, b = 67.9 and c = 109.0 ?. DWL differed in potency from other ConA-like lectins and was found to induce neutrophil migration in rats, making it particularly useful in structural/functional studies of this class of proteins. 相似文献
100.
Corma A Boronat M Climent MJ Iborra S Montón R Sabater MJ 《Physical chemistry chemical physics : PCCP》2011,13(38):17255-17261
A series of bifunctional organic catalysts containing acid and basic sites with ionic liquid characteristics have been prepared and their catalytic activity and reaction coordinate for aldol and Knoevenagel condensations have been compared. While the only factor controlling catalyst activity for the Knoevenagel condensation was the distance between the acid and base sites, the spatial orientation of the organocatalyst is also key to achieve high activity and selectivity in the Claisen-Schmidt condensation. Mechanistic studies based on theoretical DFT calculations show that the acid-base bifunctional organocatalyst follows a mechanism inspired in natural aldolases for the synthesis of trans-chalcones, being able to produce a large variety of these compounds of industrial interest. The combination of the acid-base pairs within the proper geometry and the ionic liquid nature makes this catalyst active, selective and recyclable. 相似文献