| 511. |
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| 512. |
- Valdés, Alberto, et al.
(författare)
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Shotgun proteomic analysis to study the decrease of xenograft tumor growth after rosemary extract treatment
- 2017
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1499, s. 90-100
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Tidskriftsartikel (refereegranskat)abstract
- The antiproliferative activity of Rosemary (Rosmarinus officinalis) has been widely studied in different in vitro and in vivo models, which demonstrate that rosemary extracts inhibit the cellular proliferation due to its ability to interact with a wide spectrum of molecular targets. However, a comprehensive proteomics study in vivo has not been carried out yet. In the present work, the effects of rosemary extract on xenograft tumor growth has been studied and, for the first time, a shotgun proteomic analysis based on nano-LC-MS/MS together with stable isotope dimethyl labeling (DML) has been applied to investigate the global protein changes in vivo. Our results show that the daily administration of a polyphenol-enriched rosemary extract reduces the progression of colorectal cancer in vivo with the subsequent deregulation of 74 proteins. The bioinformatic analysis of these proteins indicates that the rosemary extract mainly alters the RNA Post-Transcriptional Modification, the Protein Synthesis and the Amino Acid Metabolism functions and suggests the inactivation of the oncogene MYC. These results demonstrate the high utility of the proposed analytical methodology to determine, simultaneously, the expression levels of a large number of protein biomarkers and to generate new hypothesis about the molecular mechanisms of this extract in vivo.
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| 513. |
- van Tricht, Ewoud, et al.
(författare)
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Fast, selective and quantitative protein profiling of adenovirus-vector based vaccines by ultra-performance liquid chromatography
- 2018
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Ingår i: Journal of Chromatography A. - : ELSEVIER SCIENCE BV. - 0021-9673 .- 1873-3778. ; 1581-1582, s. 25-32
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Tidskriftsartikel (refereegranskat)abstract
- A method for the quantitative determination of the protein composition of adenovirus-vector based vaccines was developed. The final method used RP-UPLC with UV absorbance detection, a C4 column (300 angstrom, 1.7 mu m, 2.1 x 150 mm), and a water- acetonitrile (ACN) gradient containing trifluoroacetic acid (TFA) as ion-pairing agent. The chromatographic resolution between the various adenovirus proteins was optimized by studying the effect of the TFA concentration and the column temperature, applying a full factorial design of experiments. A reproducible baseline separation of all relevant adenovirus proteins could be achieved within 17 min run time. Samples containing adenovirus particles could be directly injected into the UPLC system without sample pretreatment. The viruses reproducibly dissociate into proteins in the UPLC system upon contact with the mobile phase containing ACN. The new RP-UPLC method was successfully validated for protein profiling and relative quantification of proteins in vaccine products based on adenovirus vector types 26 and 35. The intermediate precision of the relative peak areas of all proteins was between 1% and 14% RSD, except for the peak assigned to protein V (26% RSD). The method proved to be stability indicating with respect to thermal and oxidation stress of the adenovirus-vector based vaccine and was successfully implemented for the characterization of adenovirus-based products.
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| 514. |
- Veenaas, Cathrin, et al.
(författare)
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A retention index system for comprehensive two-dimensional gas chromatography using polyethylene glycols
- 2018
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1536, s. 67-74
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Tidskriftsartikel (refereegranskat)abstract
- The characterization and identification of compounds in complex real-world samples is quite difficult and new concepts and workflows are highly desirable. Retention indices (RIs) are widely used in gas chromatography (GC) to support the identification of unknown compounds. Several attempts have been made to introduce a similar concept for the second dimension in comprehensive two-dimensional (2D) GC (GC × GC) but, an easily applicable and robust system remains elusive. In the present study, a new RI system for GC × GC was developed. Polyethylene glycols (PEGs) were used in combination with a simple linear regression, with n-alkanes as reference points for virtually unretained compounds and PEG homologs as reference compounds for second-dimension RIs (PEG-2I). The n-alkanes were assigned a PEG-2I of zero and the distance between consecutive PEG homologs from PEG-2 (diethylene glycol) and higher were assigned a PEG-2I value of 10. We used ethylene glycol and PEG-2 through PEG-10 as reference compounds, thereby covering a PEG-2I range from 20.0 for ethylene glycol, over 50.0 for diethylene glycol (PEG-2) to 130.0 for decaethylene glycol (PEG-10); additional PEGs can be added to cover a wider polarity range. The PEG-2I system was initially evaluated using a 30 m × 0.25 mm non-polar (5% phenyl, 0.25 μm film thickness) first-dimension column and a 1.6 m × 0.18 mm polar (50% phenyl, 0.18 μm film thickness) second-dimension column. This system was validated for use with non-polar first-dimension columns and a semi-polar (50% phenyl) second-dimension column, and exhibited robustness to changes in the carrier gas flow velocity, oven temperature ramping rate, and secondary oven temperature offset. An average relative standard deviation of 2.7%, equal to a 95% confidence interval of 1.27 PEG-2I units, was obtained for the PEG-2I values of 72 environmental pollutants. Additionally, the system was found to be applicable over a wide range of boiling points (in the current case, from n-heptane to n-dotriacontane (C7-C32)) and can be used with various column dimensions. Changing the second-dimension column to either a narrower 0.1 mm column or a wider 0.25 mm column, yielded similar 95%-percentiles to that of the 0.18 mm column, differing by only 3.20 and 2.80 PEG-2I units, respectively. Moreover, methods for improving the system were suggested.
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| 515. |
- Vestergren, Robin, et al.
(författare)
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A matrix effect-free method for reliable quantification of perfluoroalkyl carboxylic acids and perfluoroalkane sulfonic acids at low parts per trillion levels in dietary samples
- 2012
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1237, s. 64-71
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Tidskriftsartikel (refereegranskat)abstract
- In recent exposure modeling studies diet has been identified as the dominant pathway of human exposure to perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). However, the paucity of highly sensitive and accurate analytical data to support these studies means that their conclusions are open to question. Here a novel matrix effect-free method is described for ultra-trace analysis of perfluoroalkyl carboxylic acids and perfluoroalkane sulfonic acids in dietary samples of varied composition. The method employs ion pair extraction of the analytes into methyl tert-butyl ether and subsequent solid phase extraction clean-up on Florisil and graphitized carbon. The target compounds are separated and detected using ultra performance liquid chromatography coupled to tandem mass spectrometry. Special care was taken to avoid procedural blank contamination and potential contamination sources were elucidated. The performance of the method was validated for five different food test matrices including a duplicate diet sample. Method detection limits in the low to sub pg g(-1) range were obtained for all target analytes, which is 5-100 times more sensitive than previously reported for duplicate diet samples. Total method recoveries were consistently between 50 and 80% for all analytes in all tested food matrices and effects of co-extracted matrix constituents on ionization of the target compounds were found to be negligible. The precision of the method (defined as percentage relative standard deviation) at concentrations close to the respective method limits of quantification was <15% for all analytes. Accurate quantification at ultra-trace levels was demonstrated by laboratory control spike experiments. For the first time the presence of long-chain PFCAs in duplicate diet samples is reported. The method presented here can thus support an improved assessment of human exposure from dietary intake for a range of PFCA and PFSA homologues. Re-analysis of duplicate diet samples, which had been analyzed earlier using another analytical methodology, indicated that dietary intake of PFOA and PFOS may previously have been overestimated.
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| 516. |
- Viberg, Peter, et al.
(författare)
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Continuous full filling capillary electrochromatography: Chromatographic performance and reproducibility
- 2007
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1154:1-2, s. 386-389
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Tidskriftsartikel (refereegranskat)abstract
- Continuous full filling capillary electrochromatography with nanoparticles as pseudostationary phase interfaced with electrospray ionisation mass spectrometric detection was used for reversed phase separations with very high separation efficiency. Several batches of nanoparticles were synthesised and their electrochromatographic performance were evaluated. Different parameters, such as repeatability, reproducibility, limit of detection, and peak asymmetry, were investigated yielding excellent results. The stability of the system over wide pH ranges and over time was found to be excellent. Very high separation efficiencies with over 1.1 million theoretical plates per metre were obtained. The limit of detection for the investigated dialkyl phthalates was approximately 1.0 mu mol L-1, corresponding to 3-5 fmol injected. After preparation, nanoparticle suspensions could be used without further treatment for at least an entire working day with maintained chromatographic qualities. (c) 2007 Elsevier B.V. All rights reserved.
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| 517. |
- Viberg, Peter, et al.
(författare)
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On-line capillary based quantitative analysis of a heterocyclic amine in human urine
- 2006
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1133:1-2, s. 347-352
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Tidskriftsartikel (refereegranskat)abstract
- A high through-put miniaturised separation-quantification method for the heterocyclic aromatic amine 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in urine was developed. The limit of detection was of 0.65 fmol (0.14 pg) injected or 65 pM. Heterocyclic aromatic amines are mutagenic and carcinogenic compounds formed at low levels in protein-rich food during cooking. Due to the low concentrations and the high complexity of the matrix in which they exist (food, blood, and urine), and the often small sample volumes (capillary blood; urine, blood and milk from small animals), very sensitive and selective analytical methods are required for their detection. Miniaturisation was accomplished by micro solid-phase extraction in capillaries with blue chitin as solid-phase, coupled on-line (in-capillary) to capillary electrophoresis with nanospray tandem mass spectrometric detection. This new technique provided a total analysis time of only 15 min, including extraction and separation, together with low sample and solvent consumption. Blue chitin showed high tolerance towards the urine matrix. Urine collected 12 h after consumption of fried chicken contained 1.8 nmol L-1 (0.40 pg mu L-1) of PhIP. (c) 2006 Elsevier B.V. All rights reserved.
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| 518. |
- Vidal, Lorena, et al.
(författare)
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Quaternary ammonium-functionalized silica sorbents for the solid-phase extraction of aromatic amines under normal phase conditions
- 2013
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Ingår i: Journal of Chromatography A. - : Elsevier. - 0021-9673 .- 1873-3778. ; 1285, s. 7-14
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Tidskriftsartikel (refereegranskat)abstract
- Quaternary ammonium-functionalized silica materials were synthesized and applied for solid-phase extraction (SPE) of aromatic amines, which are classified as priority pollutants by US Environmental Protection Agency. Hexamethylenetetramine used for silica surface modification for the first time was employed as SPE sorbent under normal phase conditions. Hexaminium-functionalized silica demonstrated excellent extraction efficiencies for o-toluidine, 4-ethylaniline and quinoline (recoveries 101-107%), while for N,N-dimethylaniline and N-isopropylaniline recoveries were from low to moderate (14-46%). In addition, the suitability of 1-alkyl-3-(propyl-3-sulfonate) imidazolium-functionalized silica as SPE sorbent was tested under normal phase conditions. The recoveries achieved for the five aromatic amines ranged from 89 to 99%. The stability of the sorbent was evaluated during and after 150 extractions. Coefficients of variation between 4.5 and 10.2% proved a high stability of the synthesized sorbent.Elution was carried out using acetonitrile in the case of hexaminium-functionalized silica and water for 1-alkyl-3-(propyl-3-sulfonate) imidazolium-functionalized silica sorbent.After the extraction the analytes were separated and detected by liquid chromatography ultraviolet detection (LC-UV). The retention mechanism of the materials was primarily based on polar hydrogen bonding and π-π interactions. Comparison made with activated silica provedthe quaternary ammonium-functionalized materials to offer different selectivity and better extraction efficiencies for aromatic amines. Finally, 1-alkyl-3-(propyl-3-sulfonate) imidazolium-functionalized silica sorbent was successfully tested for the extraction of wastewater and soil samples.
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| 519. |
- Vikingsson, Svante, et al.
(författare)
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Retention of opioids and their glucuronides on a combined zwitterion and hydrophilic interaction stationary phase
- 2008
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Ingår i: Journal of Chromatography A. - : Elsevier Science B.V., Amsterdam.. - 0021-9673 .- 1873-3778. ; 1187:01-Feb, s. 46-52
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Tidskriftsartikel (refereegranskat)abstract
- A stationary phase combining zwitterionic ion chromatography and hydrophilic interaction chromatography (ZIC-HILIC) from SeQuant was evaluated for the chromatography of some opiates and their polar metabolites. The effects of mobile phase constitution on retention and resolution were extensively evaluated. Different aspects of mobile phase constitution such as ion strength and type of buffer, type and amount of organic modifier and pH were examined. The selectivity and retention of the opiates compared to their glucuronides could be substantially altered with small changes of the mobile phase, especially when the type of buffer, i.e., formate, or acetate and organic modifier, i.e., acetonitrile or methanol were changed. The retention on the ZIC-HILIC was dominated by hydrophilic interaction chromatography (HILIC) but considerable effects on the selectivity was observed, possibly caused by an ion exchange mechanism due to interactions with the charges on the stationary phase.
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| 520. |
- Vilaplana, Francisco, et al.
(författare)
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Analysis of brominated flame retardants in styrenic polymers : Comparison of the extraction efficiency of ultrasonication, microwave-assisted extraction and pressurised liquid extraction
- 2008
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1196:1-2, s. 139-146
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Tidskriftsartikel (refereegranskat)abstract
- The extraction efficiency of pressurised liquid extraction (PLE), microwave-assisted extraction (MAE), and ultrasonic-assisted extraction (UAE) under different conditions has been compared for the recovery of the most commonly employed brominated flame retardants (BFRs) from styrenic polymeric Matrixes. A HPLC-MS/MS method has been proposed for the simultaneous separation and quantification of tetrabromobisphenol A (TBBPA), hexabromocyclododecane (HBCD) diastereomers, and decabromodiphenyl ether (deca-BDE) in the polymeric extracts. PLE results in complete extraction of TBBPA and HBCD (95-100% recovery), and intermediate recovery Fates for deca-BDE (50%). MAE, on the other hand, gives comparable performance to PLE for HBCD, but lower extraction yields for TBBPA and mainly deca-BDE. Ultrasonication, finally, offers relatively low extraction recoveries (10-50%). The proposed analytical procedures could be used for the effective identification and quantification of BFRs in styrenic plastics and for quality purposes in recycling facilities that deal with styrenic fractions from waste electrical and electronic equipment (WEEE).
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