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1.
Karlsson NG Schulz BL Packer NH 《Journal of the American Society for Mass Spectrometry》2004,15(5):659-672
Neutral O-linked oligosaccharides released from the salivary mucin MUC5B were separated and detected by negative ion LC-MS and LC-MS(2). The resolution of the chromatography and the information obtained from collision induced dissociation of detected [M - H](-) ions were usually sufficient to identify the sequence of individual oligosaccharides, illustrated by the fact that 50 different oligosaccharides ranging from disaccharides to nonasaccharides could be assigned from the sample. Fragmentation was shown to yield mostly reducing end sequence fragments (Z(i) and Y(i)), enabling primary sequence assignment. Specific fragmentation pathways or patterns were also detected giving specific linkage information. The reducing end core (Gal/GlcNAcbeta1-3GalNAcol or Gal/GlcNAcbeta1-3(GlcNAcbeta1-6)GalNAcol) could be deduced from the pronounced glycosidic C-3 cleavage and A(i) type cleavages of the reducing end GalNAcol, together with the non reducing end fragment from the loss of a single substituted GalNAcol. Substitution patterns on GlcNAc residues were also found, indicative for C-4 substitution ((0,2)A(i) - H(2)O cleavage) and disubstitution of C-3 and C-4 (Z(i)/Z(i) cleavages). This kind of fragmentation can be used for assigning the mode of chain elongation (Galbeta1-3/4GlcNAcbeta1-) and identification of Lewis type antigens like Lewis a/x and Lewis b/y on O-linked oligosaccharides. In essence, negative ion LC-MS(2) was able to generate extensive data for understanding the overall glycosylation pattern of a sample, especially when only a limited amount of material is available. 相似文献
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Dr. Samuel Oger Damien Schapman Dr. Romain Mougeot Dr. Stéphane Leleu Dr. Noëlle Lascoux Dr. Patrice Baldeck Dr. Magalie Bénard Dr. Thibault Gallavardin Dr. Ludovic Galas Dr. Xavier Franck 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(46):10954-10964
Epicocconone 1 is a natural chromophore isolated from the fungus Epicoccum nigrum that has shown applications in proteomics and fluorescent microscopy thanks to its unique pro-fluorescence properties. The modification of the skeleton of the natural product by replacing the triene side chain by a fluorenyl scaffold can noticeably increase the fluorophore's absorption coefficient. The synthesis of the analogues of the natural product has been made possible by the use of a palladium-catalyzed carbonylation reaction, allowing the construction of the β-keto-dioxinone key intermediate. Two-photon absorption cross-section measurements of the fluorenyl epicocconone analogues show a structure dependency with values ranging from 60 to 280 GM and live cell imaging show intense staining of intracellular vesicle-like structures around the nucleus. 相似文献
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Analysis of mucosal mucins separated by SDS-urea agarose polyacrylamide composite gel electrophoresis 总被引:1,自引:0,他引:1
Efficient separation of mucins (200 kDa-2 MDa) was demonstrated using gradient SDS agarose/polyacrylamide composite gel electrophoresis (SDS-AgPAGE). Inclusion of urea (SDS-UAgPAGE) in the gels casting were shown to have no effect on the migration of mucins in the gel and allowed casting of gel at room temperature. This simplified the procedure for multiple casting of agarose polyacrylamide gradients and increased reproducibility of these gels. Hence, the implementation of urea makes the technique applicable for high throughput isolation and screening of mucin oligosaccharides by LC-MS after releasing the oligosaccharides from isolated, blotted mucin subpopulations. It was also shown that the urea addition had no effect on other supporting applications such as western and lectin blotting. In addition, identification of the mucin protein after tryptic digestion and LC-MS was possible and no protein carbamylation due to the presence of urea in the gel was detected. LC-MS software developed for metabolomic analysis was used for O-linked oligosaccharide detection and differential display of various mucin samples. Using this method, heterogeneous glycosylation of mucins and mucin-type molecules isolated by SDS-AgPAGE and SDS-UAgPAGE was shown to consist of more than 80 different components in a single band, and in the extreme cases, up to 300-500 components (MUC5B/AC from saliva and sputum and). Metabolomic software was also used to show that the migration of mucin isoforms within the gel is due to heterogeneous size distribution of the oligosaccharides, with the slower migrating bands enriched in high-molecular-weight oligosaccharides. 相似文献
5.
Daniel M. BrumClaudio F. Lima Nicolle F. RobainaTeresa Cristina O. Fonseca Ricardo J. Cassella 《Spectrochimica Acta Part B: Atomic Spectroscopy》2011,66(5):338-344
The present paper reports the optimization for Cu, Fe and Pb determination in naphtha by graphite furnace atomic absorption spectrometry (GF AAS) employing a strategy based on the injection of the samples as detergent emulsions. The method was optimized in relation to the experimental conditions for the emulsion formation and taking into account that the three analytes (Cu, Fe and Pb) should be measured in the same emulsion. The optimization was performed in a multivariate way by employing a three-variable Doehlert design and a multiple response strategy. For this purpose, the individual responses of the three analytes were combined, yielding a global response that was employed as a dependent variable. The three factors related to the optimization process were: the concentration of HNO3, the concentration of the emulsifier agent (Triton X-100 or Triton X-114) in aqueous solution used to emulsify the sample and the volume of solution. At optimum conditions, it was possible to obtain satisfactory results with an emulsion formed by mixing 4 mL of the samples with 1 mL of a 4.7% w/v Triton X-100 solution prepared in 10% v/v HNO3 medium. The resulting emulsion was stable for 250 min, at least, and provided enough sensitivity to determine the three analytes in the five samples tested. A recovery test was performed to evaluate the accuracy of the optimized procedure and recovery rates, in the range of 88-105%; 94-118% and 95-120%, were verified for Cu, Fe and Pb, respectively. 相似文献
6.
Sandra Chouzier Tivadar Czeri Magalie Roy-Auberger Christophe Pichon Christophe Geantet Michel Vrinat Pavel Afanasiev 《Journal of solid state chemistry》2011,184(10):2668-2677
Decomposition of ammonium heptamolybdate–hexamethylentetramine (HMTA) complex (HMTA)2(NH4)4Mo7O24·2H2O was studied as a function of treatment conditions in the range 300–1173 K. The evolution of solid products during decomposition was studied by thermal analysis and in situ EXAFS. Depending on the nature of the gas used for treatment, single phases of highly dispersed nitrides Mo2N, carbide Mo2C, or oxide MoO2 can be obtained. The nature of the products obtained was explained by qualitative thermodynamical considerations. Morphology of the solids considerably depends on such preparation parameters as temperature and mass velocity of the gas flow. For the nitride-based materials, catalytic activity was evaluated in the model thiophene HDS reaction. It was demonstrated that NH3-treated samples showed better catalytic activity than N2-treated ones due to cleaner surface and better morphology. Transmission microscopy, XRD and XPS studies showed that MoS2 is formed on the surface during HDS reaction or sulfidation with H2S. Optimized nitride-derived catalysts showed mass activity several times higher than unsupported MoS2 or MoS2/Al2O3 reference catalyst. 相似文献
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An automated on-line method for the determination of the substituted aniline compounds was developed using in-tube solid-phase microextraction coupling to high-performance liquid chromatography (HPLC). In this work, oxidized multiwalled carbon nanotubes (MWCNTs-COOH) coated on the outer surface of the fused-silica tube and inserted in the polyether ether ketone (PEEK) tubing, which was fixed directly on the six-port injection valve to substitute for the sample loop. The extraction procedure was performed by a constant flow pump frequently driving the sample solution through the PEEK tubing and the analytes were adsorbed onto MWCNTs-COOH materials when the six-port valve set to load position. After extraction, the valve switched to inject position and the extracted analytes were desorbed by mobile phase in dynamic mode. High extraction capacity was achieved for the investigated analytes and great improvement of the limits of detection was obtained in comparison with other methods. The calibration plots were linear (r(2)> or =0.9949) over the concentration range of 1.04-104ngmL(-1) for 4-nitroaniline, 1.02-102ngmL(-1) for 2-nitroaniline, 1.68-168ngmL(-1) for 2-chloroaniline and 1.09-109ngmL(-1) for 2,4-dichloroaniline. The detection limit ranged from 0.04ngmL(-1) to 0.13ngmL(-1) (at S/N=3). The possibility of applying the established method to water samples analysis was also studied. 相似文献
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Stereoselective Synthesis of Functionalized Pyrrolidines by the Diverted N−H Insertion Reaction of Metallocarbenes with β‐Aminoketone Derivatives
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Simon M. Nicolle Dr. William Lewis Prof. Dr. Christopher J. Hayes Prof. Dr. Christopher J. Moody 《Angewandte Chemie (International ed. in English)》2016,55(11):3749-3753
A highly stereoselective route to functionalized pyrrolidines by the metal‐catalyzed diverted N?H insertion of a range of diazocarbonyl compounds with β‐aminoketone derivatives is described. A number of catalysts (rhodium(II) carboxylate dimers, copper(I) triflate, and an iron(III) porphyrin) are shown to promote the process under mild conditions to give a wide range of highly substituted proline derivatives. The reaction starts as a metallocarbene N?H insertion but is diverted by an intermolecular aldol reaction. 相似文献
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Richardson RD Desaize M Wirth T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(23):6745-6754
By detailed study of the possible side reactions in the previously reported aziridination of alkenes with N-aminoheterocycles mediated by hypervalent iodine reagents, the requirements to make this reaction catalytic in iodoarene have been determined. The reaction requires an oxidant that will oxidise iodoarenes but that does not oxidise alkenes, but it is possible that no such oxidant actually exists! A method in which the hypervalent iodine reagent can be recycled without the need for reisolation is possible. Further study into the mechanism of this reaction gives tentative evidence that the reaction proceeds through formation of an aminoiodane that reacts directly with the alkene, contrary to previous literature reports in which an acetoxyamine intermediate is suggested. The temperature effect of this reaction is remarkable. 相似文献
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Hoffart DJ Habermehl NC Loeb SJ 《Dalton transactions (Cambridge, England : 2003)》2007,(27):2870-2875
The ligand 4,4'-bipyridine-N-monoxide, (BIPYMO) coordinates through the pyridine N-donor to Pt(II) and Pd(II) to form square planar [ML(4)](2+) complexes and to Cu(II) and Zn(II) to form octahedral trans-[M(H(2)O)(2)L(4)](2+) complexes. Single crystal X-ray structures show that these individual building blocks are organized via hydrogen bonding through the external N-oxide O-atoms to form 2D and 3D networks. 相似文献