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https://www.readbyqxmd.com/read/27661059/three-short-stories-about-hexaarylbenzene-porphyrin-scaffolds
#1
Dominik Lungerich, Jakob F Hitzenberger, Wolfgang Donaubauer, Thomas Drewello, Norbert Jux
A feasible two-step synthesis and characterization of a full series of hexaarylbenzene (HAB) substituted porphyrins and tetrabenzoporphyrins is presented. Key steps represent the microwave-assisted porphyrin condensation and the statistical Diels-Alder reaction to the desired HAB-porphyrins. Regarding their applications, they proved to be easily accessible and effective high molecular mass calibrants for (MA)LDI mass spectrometry. The free-base and zinc(II) porphyrin systems, as well as the respective tetrabenzoporphyrins, demonstrate in solid state experiments strong red- and near-infrared-light emission and are potentially interesting for the application in "truly organic" light-emitting devices...
November 14, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27496220/linear-mass-scans-in-quadrupole-ion-traps-using-the-inverse-mathieu-q-scan
#2
Dalton T Snyder, Christopher J Pulliam, R Graham Cooks
RATIONALE: Secular frequency scanning is a method of mass selectively scanning ions out of a quadrupole ion trap by linearly ramping the frequency of the resonance ejection signal through ion secular frequencies at constant rf amplitude and frequency. The method is electronically much simpler than resonance ejection but it requires a complex nonlinear calibration procedure to correlate mass-to-charge with time. METHODS: A method of secular frequency scanning in quadrupole ion traps is described in which mass-to-charge is linear with time...
November 30, 2016: Rapid Communications in Mass Spectrometry: RCM
https://www.readbyqxmd.com/read/27479448/electrospray-differential-mobility-hyphenated-with-single-particle-inductively-coupled-plasma-mass-spectrometry-for-characterization-of-nanoparticles-and-their-aggregates
#3
Jiaojie Tan, Jingyu Liu, Mingdong Li, Hind El Hadri, Vincent A Hackley, Michael R Zachariah
The novel hyphenation of electrospray-differential mobility analysis with single particle inductively coupled plasma mass spectrometry (ES-DMA-spICPMS) was demonstrated with the capacity for real-time size, mass, and concentration measurement of nanoparticles (NPs) on a particle-to-particle basis. In this proof-of-concept study, the feasibility of this technique was validated through both concentration and mass calibration using NIST gold NP reference materials. A detection limit of 10(5) NPs mL(-1) was determined under current experimental conditions, which is about 4 orders of magnitude lower in comparison to that of a traditional ES-DMA setup using a condensation particle counter as detector...
September 6, 2016: Analytical Chemistry
https://www.readbyqxmd.com/read/27320213/optimizing-sequence-coverage-for-a-moderate-mass-protein-in-nano-electrospray-ionization-quadrupole-time-of-flight-mass-spectrometry
#4
Ryan Matsuda, Venkata Kolli, Megan Woods, Eric D Dodds, David S Hage
Sample pretreatment was optimized to obtain high sequence coverage for human serum albumin (HSA, 66.5 kDa) when using nano-electrospray ionization quadrupole time-of-flight mass spectrometry (nESI-Q-TOF-MS). Use of the final method with trypsin, Lys-C, and Glu-C digests gave a combined coverage of 98.8%. The addition of peptide fractionation resulted in 99.7% coverage. These results were comparable to those obtained previously with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS)...
September 15, 2016: Analytical Biochemistry
https://www.readbyqxmd.com/read/27317254/improved-procedure-for-dendrimer-based-mass-calibration-in-matrix-assisted-laser-desorption-ionization-time-of-flight-mass-spectrometry
#5
Jürgen H Gross
A procedure is described that results in a substantial increase in signal intensity and in improved accuracy of positive-ion mass calibration when using commercially available kits of monodisperse dendrimers (SpheriCal(®)) in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS). The peak intensities are amplified by an admixture of 2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene] malononitrile (DCTB) matrix to the kits comprising of 9-nitroanthracene matrix, sodium trifluoroacetate, and four dendrimers...
August 2016: Analytical and Bioanalytical Chemistry
https://www.readbyqxmd.com/read/27231946/broadband-120-mhz-impedance-quartz-crystal-microbalance-qcm-with-calibrated-resistance-and-quantitative-dissipation-for-biosensing-measurements-at-higher-harmonic-frequencies
#6
Manuel Kasper, Lukas Traxler, Jasmina Salopek, Herwig Grabmayr, Andreas Ebner, Ferry Kienberger
We developed an impedance quartz crystal microbalance (QCM) approach with the ability to simultaneously record mass changes and calibrated energy dissipation with high sensitivity using an impedance analyzer. This impedance QCM measures frequency shifts and resistance changes of sensing quartz crystals very stable, accurately, and calibrated, thus yielding quantitative information on mass changes and dissipation. Resistance changes below 0.3 Ω were measured with corresponding dissipation values of 0.01 µU (micro dissipation units)...
2016: Biosensors
https://www.readbyqxmd.com/read/27197031/mass-measurement-accuracy-of-the-orbitrap-in-intact-proteome-analysis
#7
Fan Yu, Houqin Fang, Kaijie Xiao, Yan Liu, Bingbing Xue, Zhixin Tian
RATIONALE: The mass measurement accuracy (MMA) of Orbitrap mass spectrometers is 1-5 ppm according to the manufacturer's specification; yet, up to 50 ppm has been used as mass tolerance to interpret Orbitrap data in the literature. A systematic evaluation of MMA is thus necessary to find the optimal mass tolerance to be used. METHODS: Reversed-phase liquid chromatography/tandem mass spectrometry (RPLC/MS/MS) analyses of the intact E. coli proteome were carried out on a Q Exactive Orbitrap mass spectrometer coupled to a Dionex UltiMate 3000 RSLCnano system...
June 30, 2016: Rapid Communications in Mass Spectrometry: RCM
https://www.readbyqxmd.com/read/27032650/experimental-characterization-of-secular-frequency-scanning-in-ion-trap-mass-spectrometers
#8
Dalton T Snyder, Christopher J Pulliam, Joshua S Wiley, Jason Duncan, R Graham Cooks
Secular frequency scanning is implemented and characterized using both a benchtop linear ion trap and a miniature rectilinear ion trap mass spectrometer. Separation of tetraalkylammonium ions and those from a mass calibration mixture and from a pesticide mixture is demonstrated with peak widths approaching unit resolution for optimized conditions using the benchtop ion trap. The effects on the spectra of ion trap operating parameters, including waveform amplitude, scan direction, scan rate, and pressure are explored, and peaks at black holes corresponding to nonlinear (higher-order field) resonance points are investigated...
July 2016: Journal of the American Society for Mass Spectrometry
https://www.readbyqxmd.com/read/27003039/mass-spectrometric-real-time-monitoring-of-an-enzymatic-phosphorylation-assay-using-internal-standards-and-data-handling-freeware
#9
Michael Krappmann, Arjen R de Boer, Daniël R W Kool, Hubertus Irth, Thomas Letzel
RATIONALE: Continuous-flow reaction detection systems (monitoring enzymatic reactions with mass spectrometry (MS)) lack quantitative values so far. Therefore, two independent internal standards (IS) are implemented in a way that the online system stability can be observed, quantitative conversion values for substrate and product can be obtained and they can be used as mass calibration standards for high MS accuracy. METHODS: An application previously developed for the MS detection of peptide phosphorylation by cAMP-dependent protein kinase A (PKA) (De Boer et al...
April 30, 2016: Rapid Communications in Mass Spectrometry: RCM
https://www.readbyqxmd.com/read/26864519/polyalanine-a-practical-polypeptide-mass-calibration-standard-for-matrix-assisted-laser-desorption-ionization-mass-spectrometry-and-tandem-mass-spectrometry-in-positive-and-negative-mode
#10
Till Gruendling, Volker Sauerland, César Barahona, Corinna Herz, Ute Nitsch
RATIONALE: Mass calibration in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is currently obtained using mixtures of individual peptides. This procedure has several drawbacks, including laborious preparation, limited shelf life and unequal calibration mass spacing. Polyalanine, a simple to prepare polydisperse molar mass standard, alleviates these problems. METHODS: Polyalanine is prepared by the typical protocols for biological sample analytics...
March 30, 2016: Rapid Communications in Mass Spectrometry: RCM
https://www.readbyqxmd.com/read/26861497/improved-mass-resolution-and-mass-accuracy-in-tof-sims-spectra-and-images-using-argon-gas-cluster-ion-beams
#11
Hyun Kyong Shon, Sohee Yoon, Jeong Hee Moon, Tae Geol Lee
The popularity of argon gas cluster ion beams (Ar-GCIB) as primary ion beams in time-of-flight secondary ion mass spectrometry (TOF-SIMS) has increased because the molecular ions of large organic- and biomolecules can be detected with less damage to the sample surfaces. However, Ar-GCIB is limited by poor mass resolution as well as poor mass accuracy. The inferior quality of the mass resolution in a TOF-SIMS spectrum obtained by using Ar-GCIB compared to the one obtained by a bismuth liquid metal cluster ion beam and others makes it difficult to identify unknown peaks because of the mass interference from the neighboring peaks...
June 2016: Biointerphases
https://www.readbyqxmd.com/read/26542615/further-exploring-the-absorption-and-enterocyte-metabolism-of-quercetin-forms-in-the-caco-2-model-using-nano-lc-tof-ms
#12
María Del Mar Contreras, Isabel Borrás-Linares, María Herranz-López, Vicente Micol, Antonio Segura-Carretero
When using the Caco-2 intestinal model, the low uptake, intracellular presence at low levels as well as generation of trace metabolites may limit the analysis of flavonoids. To overcome these limitations, we performed a simple but sensitive methodology based on nano-LC-TOF-MS, using an on-line trapping step. The analytical method was validated for quercetin, quercetin 3-O-glucoside, and quercetin 3-O-glucuronide and the reliability for characterization using lock-mass calibration was also assessed along the linear range...
April 2016: Electrophoresis
https://www.readbyqxmd.com/read/26365870/advances-in-high-resolution-mass-spectrometry-based-on-metabolomics-studies-for-food-a-review
#13
REVIEW
Josep Rubert, Milena Zachariasova, Jana Hajslova
Food authenticity becomes a necessity for global food policies, since food placed in the market without fail has to be authentic. It has always been a challenge, since in the past minor components, called also markers, have been mainly monitored by chromatographic methods in order to authenticate the food. Nevertheless, nowadays, advanced analytical methods have allowed food fingerprints to be achieved. At the same time they have been also combined with chemometrics, which uses statistical methods in order to verify food and to provide maximum information by analysing chemical data...
2015: Food Additives & Contaminants. Part A, Chemistry, Analysis, Control, Exposure & Risk Assessment
https://www.readbyqxmd.com/read/26307137/new-isoforms-and-assembly-of-glutamine-synthetase-in-the-leaf-of-wheat-triticum-aestivum-l
#14
Xiaochun Wang, Yihao Wei, Lanxin Shi, Xinming Ma, Steven M Theg
Glutamine synthetase (GS; EC 6.3.1.2) plays a crucial role in the assimilation and re-assimilation of ammonia derived from a wide variety of metabolic processes during plant growth and development. Here, three developmentally regulated isoforms of GS holoenzyme in the leaf of wheat (Triticum aestivum L.) seedlings are described using native-PAGE with a transferase activity assay. The isoforms showed different mobilities in gels, with GSII>GSIII>GSI. The cytosolic GSI was composed of three subunits, GS1, GSr1, and GSr2, with the same molecular weight (39...
November 2015: Journal of Experimental Botany
https://www.readbyqxmd.com/read/26169134/high-throughput-workflow-for-identification-of-phosphorylated-peptides-by-lc-maldi-tof-tof-ms-coupled-to-in-situ-enrichment-on-maldi-plates-functionalized-by-ion-landing
#15
Lukáš Krásný, Petr Pompach, Marcela Strnadová, Radovan Hynek, Karel Vališ, Vladimír Havlíček, Petr Novák, Michael Volný
We report an MS-based workflow for identification of phosphorylated peptides from trypsinized protein mixtures and cell lysates that is suitable for high-throughput sample analysis. The workflow is based on an in situ enrichment on matrix-assisted laser desorption/ionization (MALDI) plates that were functionalized by TiO2 using automated ion landing apparatus that can operate unsupervised. The MALDI plate can be functionalized by TiO2 into any array of predefined geometry (here, 96 positions for samples and 24 for mass calibration standards) made compatible with a standard MALDI spotter and coupled with high-performance liquid chromatography...
June 2015: Journal of Mass Spectrometry: JMS
https://www.readbyqxmd.com/read/26044277/producing-absorption-mode-fourier-transform-ion-cyclotron-resonance-mass-spectra-with-non-quadratic-phase-correction-functions
#16
David P A Kilgour, Konstantin O Nagornov, Anton N Kozhinov, Konstantin O Zhurov, Yury O Tsybin
RATIONALE: Previously described methods for producing absorption mode Fourier transform ion cyclotron resonance (FTICR) mass spectra have all relied on the phase correction function being quadratic. This assumption has been found to be invalid for some instruments and spectra and so it has not been possible to produce absorption mode spectra for these cases. METHODS: The Autophaser algorithm has been adapted to allow nth order polynomial phase correction functions to be optimized...
June 15, 2015: Rapid Communications in Mass Spectrometry: RCM
https://www.readbyqxmd.com/read/25800182/commercial-formaldehyde-standard-for-mass-calibration-in-mass-spectrometry
#17
Jadwiga Lyczko, Daniel G Beach, Wojciech Gabryelski
Common calibration standards for mass spectrometry can be a source of many problems including instrument contamination, ionization suppression and formation of unidentified ions during subsequent analysis. In this article, we present a new approach for the calibration of mass analyzers such as a quadrupole-time-of-flight mass spectrometry using a diluted solution of commercial formaldehyde. Formaldehyde is an inexpensive and commonly used solvent, and its intrinsic polymerization leads to the formation of polyoxymethylene (POM) oligomers, which are excellent multiple calibration standards for a low-mass spectral region (up to m/z 400) in the positive and negative mode of electrospray ionization...
March 2015: Journal of Mass Spectrometry: JMS
https://www.readbyqxmd.com/read/25476399/nano-liquid-chromatography-coupled-to-time-of-flight-mass-spectrometry-for-phenolic-profiling-a-case-study-in-cranberry-syrups
#18
María del Mar Contreras, David Arráez-Román, Alberto Fernández-Gutiérrez, Antonio Segura-Carretero
A new method based on nano-liquid chromatography coupled to time-of-flight mass spectrometry (nano-LC-TOF-MS) using lock-mass calibration was developed to facilitate the accurate and routine characterization and quantification of phenolic compounds. Thus, it was applied to study cranberry syrups, in which, using negative ionization mode, a total of nine phenolic compounds were unequivocally identified using standards and 38 tentatively taking into account their retention time, accurate mass (errors<5 ppm) data and isotope pattern, as well as literature...
January 2015: Talanta
https://www.readbyqxmd.com/read/25303386/2-5-dihydroxybenzoic-acid-solution-in-maldi-ms-ageing-and-use-for-mass-calibration
#19
Anu Teearu, Signe Vahur, Uku Haljasorg, Ivo Leito, Tõiv Haljasorg, Lauri Toom
2,5-Dihydroxybenzoic acid (DHB) is one of the most widely used and studied matrix compounds in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. However, the influence of ageing of the DHB solution on the MALDI mass spectra has not been yet systematically studied. In this work, the possible changes occurring in the acidified acetonitrile/water solution of the MALDI matrix compound DHB during 1-year usage period have been monitored with MALDI-Fourier transform ion cyclotron resonance mass spectrometer (MALDI-FT-ICR-MS) and attenuated total reflectance Fourier transform infrared (ATR-FT-IR) spectroscopy...
October 2014: Journal of Mass Spectrometry: JMS
https://www.readbyqxmd.com/read/25143245/pas-cal-a-repetitive-peptide-sequence-calibration-standard-for-maldi-mass-spectrometry
#20
Stefan K Maier, Ksenia Bashkueva, Christoph Rösli, Arne Skerra, Bernhard Kuster
Mass spectrometers equipped with matrix-assisted laser desorption/ionization (MALDI-MS) require frequent multipoint calibration to obtain good mass accuracy over a wide mass range and across large numbers of samples. In this study, we introduce a new synthetic peptide mass calibration standard termed PAS-cal tailored for MALDI-MS based bottom-up proteomics. This standard consists of 30 peptides between 8 and 37 amino acids long and each constructed to contain repetitive sequences of Pro, Ala and Ser as well as one C-terminal arginine residue...
November 2014: Proteomics
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