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Faraday Discussions | Page 2

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https://read.qxmd.com/read/31184658/combating-selective-ionization-in-the-high-resolution-mass-spectral-characterization-of-complex-mixtures
#21
Ryan P Rodgers, Mmilili M Mapolelo, Winston K Robbins, Martha L Chacón-Patiño, Jonathan C Putman, Sydney F Niles, Steven M Rowland, Alan G Marshall
Direct "dilute and shoot" mass spectral analysis of complex naturally-occurring mixtures has become the "standard" analysis in environmental and petrochemical science, as well as in many other areas of research. Despite recent advances in ionization methods, that approach still suffers several limitations for the comprehensive characterization of compositionally complex matrices. Foremost, the selective ionization of highly acidic (negative electrospray ionization ((-) ESI)) and/or basic (positive electrospray ionization ((+) ESI)) species limits the detection of weakly acidic/basic species, and similar issues (matrix effects) complicate atmospheric pressure photo-ionization (APPI)/atmospheric pressure chemical ionization (APCI) analyses...
June 11, 2019: Faraday Discussions
https://read.qxmd.com/read/31173013/challenges-in-the-decomposition-of-2d-nmr-spectra-of-mixtures-of-small-molecules
#22
Afef Cherni, Elena Piersanti, Sandrine Anthoine, Caroline Chaux, Laetitia Shintu, Mehdi Yemloul, Bruno Torrésani
Analytical methods for mixtures of small molecules require specificity (is a certain molecule present in the mix?) and speciation capabilities. NMR spectroscopy has been a tool of choice for both of these issues since its early days, due to its quantitative (linear) response, sufficiently high resolving power and capabilities of inferring molecular structures from spectral features (even in the absence of a reference database). However, the analytical performances of NMR spectroscopy are being stretched by the increased complexity of the samples, the dynamic range of the components, and the need for a reasonable turnover time...
June 7, 2019: Faraday Discussions
https://read.qxmd.com/read/31169273/concluding-remarks-for-advances-in-ion-spectroscopy-faraday-discussion
#23
Jack Simons
Because the Introductory Lecture of this Faraday Discussion emphasized the recent history and exciting developments in the fields of experimental methods and applications of gaseous ion spectroscopy, these Concluding Remarks are, by design, directed somewhat more toward the roles played by theory. In discussing both the experimental and theoretical studies of gaseous ions, it is important to recognize and appreciate the delicate balance workers in the field are pursuing in terms of methodological/tool development and applications to current-day pressing problems in chemistry, physics, materials science, and biology...
June 6, 2019: Faraday Discussions
https://read.qxmd.com/read/31155629/reduced-dimensionality-hyphenated-nmr-experiments-for-the-structure-determination-of-compounds-in-mixtures
#24
Justinas Sakas, Nicholle G A Bell
For the structure determination of molecules in mixtures using NMR spectroscopy, the dispersion of 13C chemical shifts provides much needed separation of resonances in the indirectly detected dimension of 2D heterocorrelated NMR experiments. This separation is crucial for establishing networks of coupled spins by hyphenated techniques that combine hetero- and homonuclear polarisation transfers. However, as the sample complexity increases, 13C chemical shifts stop being unique, hindering spectral interpretation...
June 3, 2019: Faraday Discussions
https://read.qxmd.com/read/31155623/online-supercritical-fluid-extraction-mass-spectrometry-sfe-lc-ftms-for-sensitive-characterization-of-soil-organic-matter
#25
Yufeng Shen, Rui Zhao, Nikola Tolić, Malak M Tfaily, Errol W Robinson, Rene Boiteau, Ljiljana Paša-Tolić, Nancy J Hess
We report a novel technical approach for subcritical fluid extraction (SFE) for organic matter characterization in complex matrices such as soil. The custom platform combines on-line SFE with micro-solid phase extraction, nano liquid chromatography (LC), electrospray ionization and Fourier transform mass spectrometry (SFE-LC-FTMS). We demonstrated the utility of SFE-LC-FTMS, including results from both Orbitrap and FTICR MS, for analysis of complex mixtures of organic compounds in a solid matrix by characterizing soil organic matter in peat, a high-carbon soil...
June 3, 2019: Faraday Discussions
https://read.qxmd.com/read/31144688/influence-of-carbonaceous-species-on-aqueous-photo-catalytic-nitrogen-fixation-by-titania
#26
Yu-Hsuan Liu, Manh Hiep Vu, JeongHoon Lim, Trong-On Do, Marta C Hatzell
For decades, reports have suggested that photo-catalytic nitrogen fixation by titania in an aqueous environment is possible. Yet a consensus does not exist regarding how the reaction proceeds. Furthermore, the presence of an aqueous protonated solvent and the similarity between the redox potential for nitrogen and proton reduction suggest that ammonia production is unlikely. Here, we re-investigate photo-catalytic nitrogen fixation by titania in an aqueous environment through a series of photo-catalytic and electrocatalytic experiments...
May 30, 2019: Faraday Discussions
https://read.qxmd.com/read/31140531/systems-biology-approach-to-elucidation-of-contaminant-biodegradation-in-complex-samples-integration-of-high-resolution-analytical-and-molecular-tools
#27
Caroline Gauchotte-Lindsay, Thomas J Aspray, Mara Knapp, Umer Z Ijaz
We present here a data-driven systems biology framework for the rational design of biotechnological solutions for contaminated environments with the aim of understanding the interactions and mechanisms underpinning the role of microbial communities in the biodegradation of contaminated soils. We have considered a multi-omics approach that employs novel in silico tools to combine high-throughput sequencing data (16S rRNA amplicons) with chemical data including high-resolution analytical data generated by comprehensive two-dimensional gas chromatography (GC × GC)...
May 29, 2019: Faraday Discussions
https://read.qxmd.com/read/31140485/perspectives-on-the-future-of-multi-dimensional-platforms
#28
Gino Groeneveld, Bob W J Pirok, Peter J Schoenmakers
Two-dimensional liquid chromatography (2D-LC) formats have emerged to help address separation problems that are too complex for conventional one-dimensional LC. There are a number of obstacles to the proliferation of 2D-LC that are gradually being removed. Reliable commercial instrumentation has become available and data analysis software is being improved. Detector-sensitivity and phase-system compatibility issues can largely be solved by using active-modulation strategies. The remaining challenge, developing good and fast 2D-LC methods within a reasonable time, may be solved with smart algorithms...
May 29, 2019: Faraday Discussions
https://read.qxmd.com/read/31134248/understanding-the-structural-complexity-of-dissolved-organic-matter-isomeric-diversity
#29
Dennys Leyva, Lilian V Tose, Jacob Porter, Jeremy Wolff, Rudolf Jaffé, Francisco Fernandez-Lima
In the present work, the advantages of ESI-TIMS-FT-ICR MS to address the isomeric content of dissolved organic matter are studied. While the MS spectra allowed the observation of a high number of peaks (e.g., PAN-L: 5004 and PAN-S: 4660), over 4× features were observed in the IMS-MS domain (e.g., PAN-L: 22 015 and PAN-S: 20 954). Assuming a total general formula of CxHyN0-3O0-19S0-1, 3066 and 2830 chemical assignments were made in a single infusion experiment for PAN-L and PAN-S, respectively. Most of the identified chemical compounds (∼80%) corresponded to highly conjugated oxygen compounds (O1-O20)...
May 28, 2019: Faraday Discussions
https://read.qxmd.com/read/31123736/multivariate-analysis-applied-to-complex-biological-medicines
#30
Timothy R Rudd, Lucio Mauri, Maria Marinozzi, Eduardo Stancanelli, Edwin A Yates, Annamaria Naggi, Marco Guerrini
A biological medicine (or biologicals) is a term for a medicinal compound that is derived from a living organism. By their very nature, they are complex and often heterogeneous in structure, composition and biological activity. Some of the oldest pharmaceutical products are biologicals, for example insulin and heparin. The former is now produced recombinantly, with technology being at a point where this can be considered a defined chemical entity. This is not the case for the latter, however. Heparin is a heterogeneous polysaccharide that is extracted from the intestinal mucosa of animals, primarily porcine, although there is also a significant market for non-porcine heparin due to social and economical reasons...
May 24, 2019: Faraday Discussions
https://read.qxmd.com/read/31123727/on-the-benefits-of-using-multivariate-analysis-in-mass-spectrometric-studies-of-combustion-generated-aerosols
#31
D Duca, C Irimiea, A Faccinetto, J A Noble, M Vojkovic, Y Carpentier, I K Ortega, C Pirim, C Focsa
The intricate chemistry of the carbonaceous particle surface layer (which drives their reactivity, environmental and health impacts) results in complex mass spectra. In this respect, detailed molecular-level analysis of combustion emissions may be challenging even with high-resolution mass spectrometry. Building on a recently proposed comprehensive methodology (encompassing all stages from sampling to data reduction), we propose herein a comparative analysis of soot particles produced by three different sources: a miniCAST standard generator, a laboratory diffusion flame and a single cylinder internal combustion engine...
May 24, 2019: Faraday Discussions
https://read.qxmd.com/read/31120465/complexity-of-dissolved-organic-matter-in-the-molecular-size-dimension-insights-from-coupled-size-exclusion-chromatography-electrospray-ionisation-mass-spectrometry
#32
J A Hawkes, P J R Sjöberg, J Bergquist, L J Tranvik
This paper investigates the relationship between apparent size distribution and molecular complexity of dissolved organic matter from the natural environment. We used a high pressure size exclusion chromatography (HPSEC) method coupled to UV-Vis diode array detection (UV-DAD) and electrospray ionisation mass spectrometry (ESI-MS) in order to compare the apparent size of natural organic matter, determined by HPSEC-UV and the molecular mass determined online by ESI-MS. We found that there was a clear discrepancy between the two methods, and found evidence for an important pool of organic matter that has a strong UV absorbance and no ESI-MS signal...
May 23, 2019: Faraday Discussions
https://read.qxmd.com/read/31120463/joint-and-unique-multiblock-analysis-of-biological-data-multiomics-malaria-study
#33
Izabella Surowiec, Tomas Skotare, Rickard Sjögren, Sandra Gouveia-Figueira, Judy Orikiiriza, Sven Bergström, Johan Normark, Johan Trygg
Modern profiling technologies enable us to obtain large amounts of data which can be used later for a comprehensive understanding of the studied system. Proper evaluation of such data is challenging, and cannot be carried out by bare analysis of separate data sets. Integrated approaches are necessary, because only data integration allows us to find correlation trends common for all studied data sets and reveal hidden structures not known a priori. This improves the understanding and interpretation of complex systems...
May 23, 2019: Faraday Discussions
https://read.qxmd.com/read/31120051/characterising-polar-compounds-using-supercritical-fluid-chromatography-nuclear-magnetic-resonance-spectroscopy-sfc-nmr
#34
F H M van Zelst, S G J van Meerten, A P M Kentgens
To detect and characterise compounds in complex matrices, it is often necessary to separate the compound of interest from the matrix before analysis. In our previous work, we have developed the coupling of supercritical fluid chromatography (SFC) with nuclear magnetic resonance (NMR) spectroscopy for the analysis of nonpolar samples [Van Zelst et al., Anal. Chem., 2018, 90, 10457]. In this work, the SFC-NMR setup was successfully adapted to analyse polar samples in complex matrices. In-line SFC-NMR analysis of two N-acetylhexosamine stereoisomers was demonstrated, namely N-acetyl-mannosamine (ManNAc) and N-acetyl-glucosamine (GlcNAc)...
May 23, 2019: Faraday Discussions
https://read.qxmd.com/read/31120050/deciphering-complex-metabolite-mixtures-by-unsupervised-and-supervised-substructure-discovery-and-semi-automated-annotation-from-ms-ms-spectra
#35
Simon Rogers, Cher Wei Ong, Joe Wandy, Madeleine Ernst, Lars Ridder, Justin J J van der Hooft
Complex metabolite mixtures are challenging to unravel. Mass spectrometry (MS) is a widely used and sensitive technique for obtaining structural information of complex mixtures. However, just knowing the molecular masses of the mixture's constituents is almost always insufficient for confident assignment of the associated chemical structures. Structural information can be augmented through MS fragmentation experiments whereby detected metabolites are fragmented, giving rise to MS/MS spectra. However, how can we maximize the structural information we gain from fragmentation spectra? We recently proposed a substructure-based strategy to enhance metabolite annotation for complex mixtures by considering metabolites as the sum of (bio)chemically relevant moieties that we can detect through mass spectrometry fragmentation approaches...
May 23, 2019: Faraday Discussions
https://read.qxmd.com/read/31120047/collection-and-identification-of-an-unknown-component-from-eugenia-uniflora-essential-oil-exploiting-a-multidimensional-preparative-three-gc-system-employing-apolar-mid-polar-and-ionic-liquid-stationary-phases
#36
Danilo Sciarrone, Antonino Schepis, Gemma De Grazia, Archimede Rotondo, Filippo Alibrando, Roger Raupp Cipriano, Humberto Bizzo, Cicero Deschamps, Leonard M Sidisky, Luigi Mondello
The present research deals with the collection and structural elucidation of an unknown component, accounting for about 35% of the essential oil obtained upon distillation of the leaves of Eugenia uniflora L., harvested during summer (January, 2017) in Paraná State (Southern Brazil). A multidimensional gas chromatographic preparative system, based on the coupling of three GC systems equipped with apolar, PEG and ionic liquid-based stationary phases, was successfully applied for the isolation of the chromatographic band relative to the unknown molecule...
May 23, 2019: Faraday Discussions
https://read.qxmd.com/read/31120046/structural-analysis-of-heavy-oil-fractions-after-hydrodenitrogenation-by-high-resolution-tandem-mass-spectrometry-and-ion-mobility-spectrometry
#37
Johann Le Maître, Marie Hubert-Roux, Benoît Paupy, Sabrina Marceau, Christopher P Rüger, Carlos Afonso, Pierre Giusti
Heavy petroleum fractions such as vacuum gas oils (VGOs) are structurally and compositionally highly complex mixtures. Nitrogen species, which have a significant impact on the subsequent refining processes, are generally removed by the hydrodenitrogenation (HDN) catalytic process. The purpose of this study was to identify and characterize compounds that are refractory to the HDN process. This may allow for the examination of the effectiveness of a vacuum distillate hydrotreatment catalytic bed in removing nitrogen-containing compounds before the cracking step...
May 23, 2019: Faraday Discussions
https://read.qxmd.com/read/31120045/automatised-pharmacophoric-deconvolution-of-plant-extracts-application-to-cinchona-bark-crude-extract
#38
Laure Margueritte, Laura Duciel, Mélanie Bourjot, Catherine Vonthron-Sénécheau, Marc-André Delsuc
We present a development of the "Plasmodesma" dereplication method [Margueritte et al., Magn. Reson. Chem., 2018, 56, 469]. This method is based on the automatic acquisition of a standard set of NMR experiments from a medium sized set of samples differing by their bioactivity. From this raw data, an analysis pipeline is run and the data is analysed by leveraging machine learning approaches in order to extract the spectral fingerprints of the active compounds. The optimal conditions for the analysis are determined and tested on two different systems, a synthetic sample where a single active molecule is to be isolated and characterized, and a complex bioactive matrix with synergetic interactions between the components...
May 23, 2019: Faraday Discussions
https://read.qxmd.com/read/31119225/unraveling-the-complexity-of-complex-mixtures-by-combining-high-resolution-pharmacological-analytical-and-spectroscopic-techniques-antidiabetic-constituents-in-chinese-medicinal-plants
#39
Yong Zhao, Kenneth Thermann Kongstad, Yueqiu Liu, Chenghua He, Dan Staerk
Medicinal plants have been widely used as (poly)pharmacological remedies and constitute a rich source for antidiabetic drug discovery. In the present study, forty medicinal plant samples collected in China were tested for inhibitory activity against α-glucosidase, α-amylase, and protein-tyrosine phosphatase 1B (PTP1B). Crude ethyl acetate extracts of Dioscorea bulbifera L., Boehmeria nivea Gaudich, Tinospora sagittata Gagnep. and Persicaria bistorta (L.) Samp. showed dual inhibitory activity towards α-glucosidase and PTP1B, and were chosen for further investigation...
May 23, 2019: Faraday Discussions
https://read.qxmd.com/read/31116193/application-of-novel-solid-phase-extraction-nmr-protocols-for-metabolic-profiling-of-human-urine
#40
Daniel McGill, Elena Chekmeneva, John C Lindon, Zoltan Takats, Jeremy K Nicholson
Metabolite identification and annotation procedures are necessary for the discovery of biomarkers indicative of phenotypes or disease states, but these processes can be bottlenecked by the sheer complexity of biofluids containing thousands of different compounds. Here we describe low-cost novel SPE-NMR protocols utilising different cartridges and conditions, on both natural and artificial urine mixtures, which produce unique retention profiles useful for metabolic profiling. We find that different SPE methods applied to biofluids such as urine can be used to selectively retain metabolites based on compound taxonomy or other key functional groups, reducing peak overlap through concentration and fractionation of unknowns and hence promising greater control over the metabolite annotation/identification process...
May 22, 2019: Faraday Discussions
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