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1.
Walid Bahloul Véronique Bounor-Legaré Gérard Seytre Philippe Cassagnau 《Journal of Sol-Gel Science and Technology》2011,57(1):86-94
Study of hydrolysis-condensation reactions of titanium n-butoxide precursor into an unusual medium and non-classical conditions
was carried out. Kinetic data were reached in a temperature range of 130–250°C from FTIR, TGA–GC–MS and rheological techniques.
These results were obtained into an alkane dispersing medium, (Squalane: 2,6,10,15,19,23-hexamethyltetracosane), and compared
to the ones determined from the hydrolysis-condensation reactions of the titanium dioxide precursor carried in molten polypropylene
(PP) during extrusion process. The transposition of these knowledge to the in situ synthesis of titanium dioxide in molten
PP matrix by reactive extrusion lead to the formation of a fine dispersion of few nanometer diameter (~5 nm) of TiO2 particles. Finally, the viscoelastic behaviour of the nanocomposite has been strongly altered in the terminal relaxation
zone as permanent secondary plateau (solid-like behavior), attributed to some fractal arrangement of the inorganic domains
was observed. 相似文献
2.
Hongjuan Dong Jasmin Kemptner Martina Marchetti-Deschmann Christian Peter Kubicek Günter Allmaier 《Analytical and bioanalytical chemistry》2009,395(5):1373-1383
Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI–TOF MS) has been proved to be a powerful
tool for the identification and characterization of microorganisms based on their surface peptide/protein pattern. Because
of the complexity of microorganisms, there are no standardized protocols to acquire reproducible peptide/protein profiles
for a broad range of microorganisms and for fungi in particular. Small variations during MALDI MS sample preparation affect
the quality of mass spectra quite often. In this study, we were aiming to develop a sample preparation method for the analysis
of colored, a quite often observed phenomenon, and mycotoxin-producing Fusarium conidia spores using MALDI–TOF MS. Different washing solvent systems for light- and deep-colored (from slightly orange to
red-brown) conidia spores and connected sample deposition techniques were evaluated based on MS reproducibility and number
and intensities of peaks. As a method of choice for generation of reproducible and characteristic MALDI–TOF mass spectra,
the use of a washing process for colored Fusarium conidia spores with acetonitrile/0.5% formic acid (7/3) was found and subsequently combined with two-layer volume technique
(spores/matrix (ferulic acid) solution was deposited onto a MALDI target, and after solvent evaporation, a second matrix layer
was deposited). With the application of this sample preparation method, for deep-colored Fusarium species, 19 abundant molecular ions in the m/z range 2,000–10,000 were always detected with an S/N ratio of 3:1 or better. Finally this optimized sample preparation for
the first time provided mass spectrometric fingerprints of strongly colored Fusarium conidia spores resulting in the possibility of differentiation of such spores at the species level.
相似文献
3.
Calvano CD Aresta A Palmisano F Zambonin CG 《Analytical and bioanalytical chemistry》2007,389(7-8):2075-2084
Laser desorption ionization time-of-flight mass spectrometry (LDI–TOF MS) was used to characterize olive and sunflower oils
before and after thermally assisted oxidation in order to develop a rapid fingerprinting method for oil that contains unchanged
and oxidized components. No matrix was used to assist laser desorption, and simplified mass spectra were obtained in the mass
range of interest (m/z 500–1000), where triacyl- and diacylglycerol ions were observed. Sample preparation was reduced to dissolving oil in chloroform
saturated with NaCl. Sodiated triacylglycerols (TAGs), their epoxy/hydroxy and hydroperoxy derivatives, as well as TAGs with
shortened chain fatty acids (β-scission products) were clearly observed in the spectra. LDI–TOF MS rapidly provides semiquantitative information about the
oxidation level of edible oil, and thus represents a very useful quality control tool.
Dedicated to Professor Pier Giorgio Zambonin on the occasion of his 72nd birthday. 相似文献
4.
Mohammadreza Shariatgorji Zdenek Spacil Gianluca Maddalo Lourdes B. Cardenas Leopold L. Ilag 《Rapid communications in mass spectrometry : RCM》2009,23(23):3655-3660
Quaternary protoberberine alkaloids belong to a pharmaceutically important class of isoquinoline alkaloids associated with bactericidal, fungicidal, insecticidal and antiviral activities. As traditional medicine gains wider acceptance, quick and robust analytical methods for the screening and analysis of plants containing these compounds attract considerable interest. Thin‐layer chromatography (TLC) combined with matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) is a powerful technique but suffers from dilution of the TLC bands resulting in decreased sensitivity and masking of signals in the low‐mass region both due to addition of matrix. This study integrates for the first time conventional silica gel TLC and laser desorption ionization mass spectrometry (LDI‐MS) thus eliminating the need for any external matrix. Successful separation of berberine (Rf = 0.56) and palmatine (Rf = 0.46) from Berberis barandana including their identification by MS are demonstrated. Furthermore, a robust electrospray ionization (ESI)‐MS method utilizing residual sample from TLC for quantification of berberine applying selected reaction monitoring and standard addition method is presented. The amount of berberine in the plant root prepared for the study was determined to be 0.70% (w/w). Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
5.
Zhang J Dong X Cheng J Li J Wang Y 《Journal of the American Society for Mass Spectrometry》2011,22(7):1294-1298
In this Application Note, we describe, for the first time, the rapid analysis of hydrophobic compounds present in environmental
contaminants, which includes polycyclic aromatic hydrocarbons (PAHs) and estrogen, by matrix-assisted laser desorption/ionization
time-of-flight mass spectrometry (MALDI-TOF MS) with the use of graphene as matrix. MALDI-TOF MS with conventional matrix
has limitations in analyzing low-polarity compounds owing to their difficulty in ionization. We demonstrate that compared
with conventional matrix, graphene displays higher desorption/ionization efficiencies for PAHs, and no fragment ions are observed.
The method also holds potential in quantitative analysis. In addition, the ionization signal increases with the increasing
number of benzene rings in the PAHs, suggesting that graphene binds to PAHs via π–π stacking interactions. Furthermore, graphene
as adsorbent for solid-phase extraction of coronene from river water sample displays good performance with a detection limit
of 10–7 M. This work provides a novel and convenient method for analyzing low-polarity environmental contaminants by MALDI-TOF MS. 相似文献
6.
Glutathione peroxidase (isolated from bovine erythrocytes) and its behaviour during alkylation and enzymatic digestion were
studied by various hyphenated techniques: gel electrophoresis–laser ablation (LA) inductively coupled plasma (ICP) mass spectrometry
(MS), size-exclusion liquid chromatography–ICP MS, capillary high-performance liquid chromatography (capHPLC)–ICP MS, matrix-assisted
laser desorption/ionization (MALDI) time-of-flight (TOF) MS, electrospray MS, and nanoHPLC–electrospray ionization (ESI) MS/MS.
ESI TOF MS and MALDI TOF MS allowed the determination of the molecular mass but could not confirm the presence of selenium
in the protein. The purity of the protein with respect to selenium species could be evaluated by LA ICP MS and size-exclusion
chromatography (SEC)–ICP MS under denaturating and nondenaturating conditions, respectively. SEC–ICP MS and capHPLC–ICP MS
turned out to be valuable techniques to study the enzymolysis efficiency, miscleavage and artefact formation during derivatization
and tryptic digestion. For the first time the parallel ICP MS and ESI MS/MS data are reported for the selenocysteine-containing
peptide extracted from the gel; capHPLC–ICP MS allowed the sensitive detection of the selenopeptide regardless of the matrix
and nanoHPLC–electrospray made possible its identification.
Figure Eye catching image
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
7.
M. Careri L. Elviri A. Lorenzi A. Mangia A. Penna G. Predieri 《Journal of Sol-Gel Science and Technology》2011,60(3):359-365
In this work, sol–gel derived silica films were prepared for direct desorption/ionization of organic compounds in MALDI-TOF–MS
analysis with the aim of improving method precision and of reducing interfering signals at low m/z values. Two commonly used
MALDI matrices, 2,5-dihydroxybenzoic acid (DHB) and α-cyano-4-hydroxycinnamic acid (CHCA), were incorporated into the sol–gel
network in order to absorb laser energy and to induce analyte desorption/ionization with low or absent background signals
in the mass spectra. To achieve a reproducible xerogel film formation, experimental parameters for its deposition were optimized.
The gel matrices were characterized by Fourier Transform Infrared (FT-IR) spectroscopy, X-ray Diffraction (XRD), and Scanning
Electron Microscopy (SEM) analysis. The results proved the embedding of the matrix molecules in a disperse form into the homogeneous
sol–gel material. The sol–gel matrix was then tested for the qualitative and quantitative analysis of two reference peptides,
such as Bradykinin and P14R. In addition, spectral quality and method performance were assessed for quantitation of melamine, a low-molecular weight
compound of food safety concern. In all cases, high quality spectra and excellent mass accuracy (between 3.5 and 13 ppm) were
observed. Furthermore, the experimental results evidenced a significant improvement of the measurement repeatability on spot
and between spots (relative standard deviation <10%), with respect to the traditional dried-droplet sample deposition method.
Good sensitivity and linearity in the concentration range explored were obtained for peptides and melamine, demonstrating
the suitability of the sol–gel-based matrix to be used for quantitative analysis. 相似文献
8.
The desorption of oxygen from polycrystalline palladium (Pd(poly)) was studied using temperature-programmed desorption (TPD)
at 500–1300 K and the amounts of oxygen absorbed by palladium (n) from 0.05 to 50 monolayers. It was found that the desorption of O2 from Pd(poly), which occurred from a chemisorbed oxygen layer (Oads), in the release of oxygen from a near-surface metal layer in the course of the decomposition of PdO surface oxide, and in
the release of oxygen from the bulk of palladium (Oabs), was governed by repulsive interactions between Oads atoms and the formation and decomposition of Oads-Pd*-Oabs structures (Pd* is a surface palladium atom). At θ ≤ 0.5, the repulsive interactions between Oads atoms (ɛaa = 10 kJ/mol) resulted in the desorption of O2 from Pd(poly) at 650–950 K. At 0.5 ≤ n ≤ 1.0, the release of inserted oxygen from a near-surface palladium layer occurred during TPD in the course of the migration
of Oabs atoms to the surface and the formation-decomposition of Oads-Pd*-Oabs structures. As a result, the desorption of O2 occurred in accordance with a first-order reaction with a thermal desorption (TD) peak at T
max ∼ 700 K. At 1.0 ≤ n ≤ 2.0, the decomposition of PdO surface oxide occurred at a constant surface cover-age with oxygen during TPD in the course
of the formation-decomposition of Oads-Pd*-Oabs structures. Because of this, the desorption of O2 occurred in accordance with a zero-order reaction at low temperatures with a TD peak at T
max ∼ 675 K. At 1.0 ≤ n ≤ 50, oxygen atoms diffused from deep palladium layers in the course of TPD and arrived at the surface at high temperatures.
As a result, O2 was desorbed with a high-temperature TD peak at T > 750 K. 相似文献
9.
Sedimentation field-flow fractionation–inductively coupled plasma–mass spectrometry (SdFFF-ICP-MS) was successfully applied
to investigate particle size distribution of titanium dioxide (TiO2) in sunscreen samples after hexane extraction to remove organic components from the samples. Three brands of sunscreen products
of various sun protection factor (SPF) value were used as samples. Different particle size distribution profiles were observed
for sunscreen samples of various brands and SPF values; however, the particle size distributions of titanium dioxide in most
sunscreen samples investigated in this work were larger than 100 nm. The titanium dioxide concentrations were higher for the
products of higher SPF values. By comparing the results obtained from online SdFFF-ICP-MS and those from the off-line ICP-MS
determination of titanium after acid digestion, ICP-MS was found to effectively atomize and ionize the titanium dioxide particle
without the need for acid digestion of the samples. Therefore, the online coupling between SdFFF and ICP-MS could be effectively
used to provide quantitative information of titanium dioxide concentrations across particle size distribution profiles. 相似文献
10.
Mohammad Muneer Mohd Saquib Mohd Qamar Detlef Bahnemann 《Research on Chemical Intermediates》2010,36(2):121-125
The photocatalyzed oxidation of indole (1) in an aqueous suspension of titanium dioxide has been investigated and an attempt has been made to identify the products
formed during the photooxidation process by gas chromatographic–mass spectrometric (GC–MS) analysis. Photolysis of an aqueous
solution of indole (1) in the presence of titanium dioxide and oxygen led to the formation of 2,3-dihydroindole-2-one (6) and 1H-indole-2,3-dione (7). A probable pathway for the formation of these products has been proposed. 相似文献
11.
Sogawa K Watanabe M Sato K Segawa S Ishii C Miyabe A Murata S Saito T Nomura F 《Analytical and bioanalytical chemistry》2011,400(7):1905-1911
In a clinical diagnosis microbiology laboratory, the current method of identifying bacterial isolates is based mainly on phenotypic
characteristics, for example growth pattern on different media, colony morphology, Gram stain, and various biochemical reactions.
These techniques collectively enable great accuracy in identifying most bacterial isolates, but are costly and time-consuming.
In our clinical microbiology laboratory, we prospectively assessed the ability of matrix-assisted laser desorption ionization–time
of flight mass spectrometry (MALDI–TOF MS) to identify bacterial strains that were routinely isolated from clinical samples.
Bacterial colonies obtained from a total of 468 strains of 92 bacterial species isolated at the Department of Clinical Laboratory
at Chiba University were directly placed on target MALDI plates followed by addition of CHCA matrix solution. The plates were
then subjected to MALDI–TOF MS measurement and the microorganisms were identified by pattern matching with the libraries in
the BioTyper 2.0 software. Identification success at the species and genus levels was 91.7% (429/468) and 97.0% (454/468),
respectively. MALDI–TOF MS is a rapid, simple, and high-throughput proteomic technique for identification of a variety of
bacterial species. Because colony-to-colony differences and effects of culture duration on the results are minimal, it can
be implemented in a conventional laboratory setting. Although for some pathogens, preanalytical processes should be refined,
and the current database should be improved to obtain more accurate results, the MALDI–TOF MS based method performs, in general,
as well as conventional methods and is a promising technology in clinical laboratories. 相似文献
12.
Martin Krappe Steven B. Hawthorne B. W. Wenclawiak 《Fresenius' Journal of Analytical Chemistry》1999,364(7):625-630
The methodology for the detection of picogram quantities of nucleotides directly from TLC plates without the use of radioactive
labeling has been developed. The method couples thin-layer chromatography (TLC) separation with matrix-assisted laser desorption/ionization
mass spectrometry (MALDI MS) detection. The TLC/MALDI coupling protocol was studied and optimized for the separation and detection
of deoxyribonucleotides. Several ammonia based solvents were examined as potential extraction solvents for the TLC/MALDI coupling
protocol. It was found that in order to obtain maximum MALDI signal intensity and minimal analyte spreading, the extraction
solvent should produce Rf-values for the analytes in the range of 0.3–0.4. Rf-values above this range led to extensive analyte spreading and those below this range resulted in poor extraction. Various
MALDI matrices and co-matrices were investigated, the best results were obtained using 2′,4′,6′-trihydroxyacetophenone (THA)
as a matrix. The extraction solvent chosen was an ammonium hydroxide/methanol (100 mM/30%, Rf = 0.28–0.38) solvent system which was found to provide the best sensitivity, minimal lateral spreading and excellent matrix
transfer. Using the optimized coupling protocol, the detection limits for the deoxyribonucleotide monophosphates were established
at or better than 10 picograms.
Received: 27 May 1998 / Revised: 18 June 1999 / Accepted: 22 June 1999 相似文献
13.
Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was optimized to discriminate
between wild-type and ampicillin-resistant Escherichia coli. Only ampicillin-resistant E. coli displayed an m/z ≈ 29,000 peak, which was confirmed as β-lactamase by in-gel digestion followed by peptide mass fingerprinting. Rapid MALDI-TOF
MS detection of antibiotic-resistance could fulfill an important clinical need, providing critical phenotypic information
beyond genus–species identification. 相似文献
14.
Nanomaterials have emerging importance in laser desorption ionization mass spectrometry (LDI–MS) with the ultimate objective
being to overcome some of the most important limitations intrinsically related to the use of conventional organic matrices
in matrix-assisted (MA) LDI–MS. This review provides a critical overview of the most recent literature on the use of gold
nanomaterials as non-conventional desorption ionization promoters in LDI–MS, with particular emphasis on bioanalytical applications.
Old seminal papers will also be discussed to provide a timeline of the most significant achievements in the field. Future
prospects and research needs are also briefly discussed. 相似文献
15.
Zimmerman TA Rubakhin SS Sweedler JV 《Journal of the American Society for Mass Spectrometry》2011,22(5):828-836
Mass spectrometry imaging (MSI) provides the ability to detect and identify a broad range of analytes and their spatial distributions
from a variety of sample types, including tissue sections. Here we describe an approach for probing neuropeptides from sparse
cell cultures using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) MSI—at single cell spatial resolution—in
both MS and tandem MS modes. Cultures of Aplysia californica neurons are grown on an array of glass beads embedded in a stretchable layer of Parafilm M. As the membrane is stretched,
the beads/neurons are separated physically and the separated beads/neurons analyzed via MALDI TOF MS. Compared with direct
MS imaging of samples, the stretching procedure enhances analyte extraction and incorporation into the MALDI matrix, with
negligible analyte spread between separated beads. MALDI tandem MSI using the stretched imaging approach yields localization
maps of both parent and fragment ions from Aplysia pedal peptide, thereby confirming peptide identification. This methodology represents a flexible platform for MSI investigation
of a variety of cell cultures, including functioning neuronal networks. 相似文献
16.
Tang XS Tang ZR Wang SP Feng ZM Zhou D Li TJ Yin YL 《Applied biochemistry and biotechnology》2012,166(3):640-651
Bovine lactoferrampin (LFA) and bovine lactoferricin (LFC) are two antimicrobial peptides located in the N1 domain of bovine lactoferrin. The bactericidal activity of the fused peptide LFA–LFC is stronger than that of either LFA
or LFC. The high cost of peptide production from either native digestion or chemical synthesis limits the clinical application
of antimicrobial peptides. The expression of recombinant peptides in yeast may be an effective alternative. In the current
study, the expression, purification, and antibacterial activity of LFA–LFC using the Pichia pastoris expression system are reported. The linearized expression vector pPICZaA–LFA–LFC was transformed into P. pastoris KM71 by electroporation, and positive colonies harboring the target genes were screened out and used for fermentation. The
recombinant LFA–LFC peptide was purified via two-step column chromatography and identified by tricine–sodium dodecyl sulfate–polyacrylamide
gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The results indicate
that P. pastoris is a suitable system for secreting LFA–LFC. The fermentation supernate and the purified LFA–LFC show high antimicrobial activities.
The current study is the first to report on the expression and purification of LFA–LFC in P. pastoris and may have potential practical applications in microbial peptide production. 相似文献
17.
Jana Chalupová Michaela Sedlářová Michaela Helmel Pavel Řehulka Martina Marchetti‐Deschmann Günter Allmaier Marek Šebela 《Journal of mass spectrometry : JMS》2012,47(8):978-986
Fast and easy identification of fungal phytopathogens is of great importance in agriculture. In this context, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) has emerged as a powerful tool for analyzing microorganisms. This study deals with a methodology for MALDI‐TOF MS‐based identification of downy and powdery mildews representing obligate biotrophic parasites of crop plants. Experimental approaches for the MS analyses were optimized using Bremia lactucae, cause of lettuce downy mildew, and Oidium neolycopersici, cause of tomato powdery mildew. This involved determining a suitable concentration of spores in the sample, selection of a proper MALDI matrix, looking for the optimal solvent composition, and evaluation of different sample preparation methods. Furthermore, using different MALDI target materials and surfaces (stainless steel vs polymer‐based) and applying various conditions for sample exposure to the acidic MALDI matrix system were investigated. The dried droplet method involving solvent evaporation at room temperature was found to be the most suitable for the deposition of spores and MALDI matrix on the target and the subsequent crystallization. The concentration of spore suspension was optimal between 2 and 5 × 109 spores per ml. The best peptide/protein profiles (in terms of signal‐to‐noise ratio and number of peaks) were obtained by combining ferulic and sinapinic acids as a mixed MALDI matrix. A pretreatment of the spore cell wall with hydrolases was successfully introduced prior to MS measurements to obtain more pronounced signals. Finally, a novel procedure was developed for direct mass spectra acquisition from infected plant leaves. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
18.
We have developed matrix pre‐coated targets for imaging proteins in thin tissue sections by matrix‐assisted laser desorption/ionization mass spectrometry. Gold covered microscope slides were coated with sinapinic acid (SA) in batches in advance and were shown to be stable for over 6 months when kept in the dark. The sample preparation protocol using these SA pre‐coated targets involves treatment with diisopropylethylamine (DIEA)‐H2O vapor, transforming the matrix layer to a viscous ionic liquid. This SA‐DIEA ionic liquid layer extracts proteins and other analytes from tissue sections that are thaw mounted to this target. DIEA is removed by the immersion of the target into diluted acetic acid, allowing SA to co‐crystallize with extracted analytes directly on the target. Ion images (3–70 kDa) of sections of mouse brain and rat kidney at spatial resolution down to 10 µm were obtained. Use of pre‐coated slides greatly reduces sample preparation time for matrix‐assisted laser desorption/ionization imaging while providing high throughput, low cost and high spatial resolution images. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
19.
The solubility of industrially produced titanium dioxide nanoparticles has been studied in aqueous sodium chloride media in
the pH range 1 to 13 at 25 °C by using adsorptive stripping voltammetry (AdSV). Kinetic dissolution curves have been obtained
as well as long-term solubilities that provide an approximation of the equilibrium solubilities. The titania nanoparticles
used in the dissolution experiments have been characterized by nitrogen sorption measurements, XRD and colloid titration.
The equilibrium solubilities and titanium(IV) speciation and their dependences on pH have been modelled by assuming the formation
of the mononuclear titanium hydroxo complexes [Ti(OH)
n
](4−n)+ (n=2 to 5) to be the only titanium species present. The solubility product of titanium dioxide and equilibrium constants for
titanium(IV) hydrolysis, calculated from the AdSV solubility data, are presented. 相似文献
20.
《Rapid communications in mass spectrometry : RCM》2004,18(17):1885-1888
The need for high‐throughput methodologies providing both qualitative and quantitative information has grown substantially in the pharmaceutical laboratory in recent years. Currently, tandem mass spectrometry (MS/MS) using quadrupole technology offers analysis in the minutes time scale. The use of matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) offers the advantage of speed and automation and enables analysis in the seconds time scale with accurate mass capabilities that are not typically found in quadrupole MS/MS. However, one of the limitations of MALDI for the analysis of small molecules is the abundance of interfering matrix peaks in the low molecular weight region of the mass spectrum. Described herein is an evaluation of a pre‐prepared MALDI target plate that has been coated with a thin layer of α‐cyano‐4‐hydroxycinnamic acid (CHCA) and nitrocellulose. This modified plate has been shown to suppress or eliminate CHCA matrix signals without any significant loss of analyte sensitivity when compared with analysis of the same sample using an unmodified target plate. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献