pinecone/core-2020-05-10-deduplication huggingface dataset:
Mass spectrometric characterization of high-valent metal-oxo, -peroxo and -peroxy intermediates of relevance in oxidation processes

The coupling of mass spectrometry with ionization techniques like electrospray ionization (ESI) or matrix-assisted matrix-assisted laser desorption-ionization (MALDI) offers many advantages over other well-established spectroscopic techniques employed for the investigation of intermediates or short-lived species in condensed-phase. In this review we describe some of the applications of mass spectrometry, in particular of ESI-MS to the detection and characterization of high-valent metal-oxo, -peroxo and -peroxy derivatives, crucial intermediates in the oxyfunctionalization of organic substrates. In addition, by utilizing gas-phase ion-molecule reactions and MS/MS experiments, information on the intrinsic reactivity of the short-lived intermediates may be obtained. The combined use of ESI-MS in association with other spectroscopic techniques and theoretical calculations is discussed as well. Â© 2006 Wiley Periodicals, Inc
Power and limitations of electrophoretic separations in proteomics strategies.

International audienceProteomics can be defined as the large-scale analysis of proteins. Due to the complexity of biological systems, it is required to concatenate various separation techniques prior to mass spectrometry. These techniques, dealing with proteins or peptides, can rely on chromatography or electrophoresis. In this review, the electrophoretic techniques are under scrutiny. Their principles are recalled, and their applications for peptide and protein separations are presented and critically discussed. In addition, the features that are specific to gel electrophoresis and that interplay with mass spectrometry (i.e., protein detection after electrophoresis, and the process leading from a gel piece to a solution of peptides) are also discussed
MS-based analytical methodologies to characterize genetically modified crops

El pdf del artículo es la versión pre-print.The development of genetically modified crops has had a great impact on the agriculture and food industries. However, the development of any genetically modified organism (GMO) requires the application of analytical procedures to confirm the equivalence of the GMO compared to its isogenic non-transgenic counterpart. Moreover, the use of GMOs in foods and agriculture faces numerous criticisms from consumers and ecological organizations that have led some countries to regulate their production, growth, and commercialization. These regulations have brought about the need of new and more powerful analytical methods to face the complexity of this topic. In this regard, MS-based technologies are increasingly used for GMOs analysis to provide very useful information on GMO composition (e.g., metabolites, proteins). This review focuses on the MS-based analytical methodologies used to characterize genetically modified crops (also called transgenic crops). First, an overview on genetically modified crops development is provided, together with the main difficulties of their analysis. Next, the different MS-based analytical approaches applied to characterize GM crops are critically discussed, and include “-omics” approaches and target-based approaches. These methodologies allow the study of intended and unintended effects that result from the genetic transformation. This information is considered to be essential to corroborate (or not) the equivalence of the GM crop with its isogenic non-transgenic counterpart.Peer Reviewe
Foodomics: MS-based Strategies in Modern Food Science and Nutrition

Modern research in food science and nutrition is moving from classical methodologies to advanced analytical strategies in which MS-based techniques play a crucial role. In this context, Foodomics has been recently defined as a new discipline that studies food and nutrition domains through the application of advanced omics technologies in which MS techniques are considered indispensable. Applications of Foodomics include the genomic, transcriptomic, proteomic, and/or metabolomic study of foods for compound profiling, authenticity, and/or biomarker-detection related to food quality or safety; the development of new transgenic foods, food contaminants, and whole toxicity studies; new investigations on food bioactivity, food effects on human health, etc. This review work does not intend to provide an exhaustive revision of the many works published so far on food analysis using MS techniques. The aim of the present work is to provide an overview of the different MS-based strategies that have been (or can be) applied in the new field of Foodomics, discussing their advantages and drawbacks. Besides, some ideas about the foreseen development and applications of MS-techniques in this new discipline are also provided. © 2011 Wiley Periodicals, Inc., Mass Spec Rev 31:49–69, 2012Ministerio de Educación y Ciencia (AGL2008-05108-C03-01 and CONSOLIDER INGENIO 2010 CSD2007-00063 FUN-C-FOOD), MICINN “Ramón y Cajal”Peer reviewe
A decade of plant proteomics and mass spectrometry: Translation of technical advancements to food security and safety issues

Tremendous progress in plant proteomics driven by mass spectrometry (MS) techniques has been made since 2000 when few proteomics reports were published and plant proteomics was in its infancy. These achievements include the refinement of existing techniques and the search for new techniques to address food security, safety, and health issues. It is projected that in 2050, the world’s population will reach 9–12 billion people demanding a food production increase of 34–70% (FAO, 2009) from today’s food production. Provision of food in a sustainable and environmentally committed manner for such a demand without threatening natural resources, requires that agricultural production increases significantly and that postharvest handling and food manufacturing systems become more efficient requiring lower energy expenditure, a decrease in postharvest losses, less waste generation and food with longer shelf life. There is also a need to look for alternative protein sources to animal based (i.e., plant based) to be able to fulfill the increase in protein demands by 2050. Thus, plant biology has a critical role to play as a science capable of addressing such challenges. In this review, we discuss proteomics especially MS, as a platform, being utilized in plant biology research for the past 10 years having the potential to expedite the process of understanding plant biology for human benefits. The increasing application of proteomics technologies in food security, analysis, and safety is emphasized in this review. But, we are aware that no unique approach/technology is capable to address the global food issues. Proteomics-generated information/resources must be integrated and correlated with other omics-based approaches, information, and conventional programs to ensure sufficient food and resources for human development now and in the futureWeb of Scienc
Identification of carotenoids using mass spectrometry

The present review compiles positive MS fragmentation data of selected carotenoids obtained using various ionization techniques and matrices. In addition, new experimental data from the analysis of carotenoids in transgenic maize and rice callus are provided. Several carotenes and oxygen-functionalized carotenoids containing epoxy, hydroxyl, and ketone groups were ionized by atmospheric pressure chemical ionization (APCI)-tandem mass spectrometry (MS/MS) in positive ion mode. Thus, on the basis of the information obtained from the literature and our own experiments, we identified characteristic carotenoid ions that can be associated to functional groups in the structures of these compounds. In addition, pigments with a very similar structure were differentiated through comparison of the intensities of their fragments. The data provide a basis for the structural elucidation of carotenoids by mass spectrometry (MS).We thank Chao Bai, Drs. Changfu Zhu and Gemma Farré (PVCF, Universitat de Lleida, Spain) for providing plant material and the Comissionat per a Universitats i Recerca del
DIUE de la Generalitat de Catalunya (Barcelona, Spain) and to
the European Social Fund (ESF) for the PhD fellowship of Sol
M. Rivera. This work was supported by the University of Lleida,
Ministry of Science and Innovation (MICINN), Spain (BFU200761413 and CTQ2009-14699-C02-01) and an ERC Advanced Grant (BIOFORCE) to Paul Christou
Numerical modeling of capillary electrophoresis : electrospray mass spectrometry interface design

Capillary electrophoresis hyphenated with electrospray mass spectrometry (CE-ESI-MS) has emerged in the past decade as one of the most powerful bioanalytical techniques. As the sensitivity and efficiency of new CE-ESI-MS interface designs are continuously improving, numerical modeling can play important role during their development. In this review, different aspects of computer modeling and simulation of CE-ESI-MS interfaces are comprehensively discussed. Relevant essentials of hydrodynamics as well as state-of-the-art modeling techniques are critically evaluated. Sheath liquid-, sheathless-, and liquid-junction interfaces are reviewed from the viewpoint of multidisciplinary numerical modeling along with details of single and multiphase models together with electric field mediated flows, electrohydrodynamics, and free fluid-surface methods. Practical examples are given to help non-specialists to understand the basic principles and applications. Finally, alternative approaches like air amplifiers are also included
Mass Spectrometry for the Elucidation of the Subtle Molecular Structure of Biodegradable Polymers and their Degradation Products

Contemporary reports by Polish authors on the application of\ud
mass spectrometric methods for the elucidation of the subtle\ud
molecular structure of biodegradable polymers and their\ud
degradation products will be presented. Special emphasis will\ud
be given to natural aliphatic (co)polyesters (PHA) and their\ud
synthetic analogues, formed through anionic ring-opening\ud
polymerization (ROP) of b-substituted b-lactones. Moreover,\ud
the application of MS techniques for the evaluation of the\ud
structure of biodegradable polymers obtained in ionic and\ud
coordination polymerization of cyclic ethers and esters as well\ud
as products of step-growth polymerization, in which bifunctional\ud
or multifunctional monomers react to form oligomers and\ud
eventually long chain polymers, will be discussed. Furthermore,\ud
the application of modern MS techniques for the assessment of\ud
polymer degradation products, frequently bearing characteristic\ud
end groups that can be revealed and differentiated by MS, will\ud
be discussed within the context of specific degradation pathways.\ud
Finally, recent Polish accomplishments in the area of\ud
mass spectrometry will be outlined
Recommendations for reporting ion mobility Mass Spectrometry measurements

Here we present a guide to ion mobility mass spectrometry experiments, which covers both linear and nonlinear methods: what is measured, how the measurements are done, and how to report the results, including the uncertainties of mobility and collision cross section values. The guide aims to clarify some possibly confusing concepts, and the reporting recommendations should help researchers, authors and reviewers to contribute comprehensive reports, so that the ion mobility data can be reused more confidently. Starting from the concept of the definition of the measurand, we emphasize that (i) mobility values (K0) depend intrinsically on ion structure, the nature of the bath gas, temperature, and E/N; (ii) ion mobility does not measure molecular surfaces directly, but collision cross section (CCS) values are derived from mobility values using a physical model; (iii) methods relying on calibration are empirical (and thus may provide method‐dependent results) only if the gas nature, temperature or E/N cannot match those of the primary method. Our analysis highlights the urgency of a community effort toward establishing primary standards and reference materials for ion mobility, and provides recommendations to do so. © 2019 The Authors. Mass Spectrometry Reviews Published by Wiley Periodicals, Inc
Kinetic and Thermodynamic Studies of Carbenium Ion Additions Towards Alkenes

The ionisation (Ar2CHCl + BC13 v=± Ar2CH+BCi;) and dissociation (Ar2CH+BCi;
^=*Ar2CH+ + BCl^) equilibria of diarylmethyl chlorides i n boron trichloride/
dichloromethane solution have been studied by conductimetry, photometry
and *H NMR spectroscopy. Small differences i n the UV-vis spectra of diarylcarbenium
tetrachloroborates, which have been observed i n solutions of low
and high tetrachloroborate concentration, can be attributed to the formation
of 1 :1 ion-pairs i n the more concentrated solutions. Low temperature calorimetry
was used to determine the heats of addition of diarylcarbenium tetrachloroborates
to 2~methyl-1 -pentene (Ar2CH+BCi; + H2C=CRRT ArjCH-CHj-CRR'Cl
+ BC13), and it is estimated that the standard free enthalpy of t h i s reaction
is greater than 0 for systems with pKR+ > -2.6. Kinetic studies have shown
that paired and unpaired diarylcarbenium tetrachloroborates exhibit identical
reactivity towards alkenes. A rationalisation for the different situation
in carbocationic and carbanionic polymerisation i s presented. The rate
constants for the initiation of isobutene, styrene and isoprene polymerisation
by diarylcarbenium ions have been determined, and it is shown, how propagation
rate constants can be estimated from linear free energy relationships.
Extension-enhanced conductivity of liquid crystalline polymer nano-composites

The article of record as published may be located at http://dx.doi.org/10.1002/masy.200551007Our aim here is to predict elongational flow-induced enhancements
in thermal or electrical conductivity of liquid crystal polymer (LCP) nanocomposites.
To do so, we combine two classical mathematical asymptotic
analyses: slender longwave hydro-thermo-dynamics for fibers and exact
analysis of pure elongation of LCPs in solvents for bulk phases without
boundary effects; and homogenization theory for effective properties of low
volume-fraction spheroidal inclusions. Two implications follow: elongational
flow dominates fiber free surface and thermal effects on electrical and thermal
conductivity enhancements; and, there appears to be no sacrifice in
enhancements by producing much higher radius, bulk fibers.Our aim here is to predict elongational flow-induced enhancements in thermal or electrical conductivity of liquid crystal polymer (LCP) nano-composites. To do so, we combine two classical mathematical asymptotic analyses: slender longwave hydro-thermo-dynamics for fibers and exact analysis of pure elongation of LCPs in solvents for bulk phases without boundary effects; and homogenization theory for effective properties of low volume-fraction spheroidal inclusions. Two implications follow: elongational flow dominates fiber free surface and thermal effects on electrical and thermal conductivity enhancements; and, there appears to be no sacrifice in enhancements by producing much higher radius, bulk fiber
Fluctuating Interfaces in Liquid Crystals

We review and compare recent work on the properties of fluctuating interfaces
between nematic and isotropic liquid-crystalline phases. Molecular dynamics and
Monte Carlo simulations have been carried out for systems of ellipsoids and
hard rods with aspect ratio 15:1, and the fluctuation spectrum of interface
positions (the capillary wave spectrum) has been analyzed. In addition, the
capillary wave spectrum has been calculated analytically within the Landau-de
Gennes theory. The theory predicts that the interfacial fluctuations can be
described in terms of a wave vector dependent interfacial tension, which is
anisotropic at small wavelengths (stiff director regime) and becomes isotropic
at large wavelengths (flexible director regime). After determining the elastic
constants in the nematic phase, theory and simulation can be compared
quantitatively. We obtain good agreement for the stiff director regime. The
crossover to the flexible director regime is expected at wavelengths of the
order of several thousand particle diameters, which was not accessible to our
simulations
3D plotted PCL scaffolds for stem cell based bone tissue engineering

The ability to control the architecture and strength of a bone tissue
engineering scaffold is critical to achieve a harmony between the scaffold and the
host tissue. Rapid prototyping (RP) technique is applied to tissue engineering to
satisfy this need and to create a scaffold directly from the scanned and digitized
image of the defect site. Design and construction of complex structures with
different shapes and sizes, at micro and macro scale, with fully interconnected pore
structure and appropriate mechanical properties are possible by using RP techniques.
In this study, RP was used for the production of poly(e-caprolactone) (PCL) scaffolds.
Scaffolds with four different architectures were produced by using different configurations
of the fibers (basic, basic-offset, crossed and crossed-offset) within the
architecture of the scaffold. The structure of the prepared scaffolds were examined by
scanning electron microscopy (SEM), porosity and its distribution were analyzed by
micro-computed tomography (m-CT), stiffness and modulus values were determined
by dynamic mechanical analysis (DMA). It was observed that the scaffolds had very
ordered structures with mean porosities about 60%, and having storage modulus
values about 1!107 Pa. These structures were then seeded with rat bone marrow
origin mesenchymal stem cells (MSCs) in order to investigate the effect of scaffold
structure on the cell behavior; the proliferation and differentiation of the cells on
the scaffolds were studied. It was observed that cell proliferation was higher on offset
scaffolds (262000 vs 235000 for basic, 287000 vs 222000 for crossed structure) and
stainings for actin filaments of the cells reveal successful attachment and spreading
at the surfaces of the fibers. Alkaline phosphatase (ALP) activity results were higher
for the samples with lower cell proliferation, as expected. Highest MSC differentiation
was observed for crossed scaffolds indicating the influence of scaffold structure on
cellular activities
Molecular architecture of non-linear polymers: kinetic modeling and experimental characterization of the system methyl methacrylate + Ethylene Glycol Dimethacrylate

A general kinetic approach allowing the prediction of the molecular architecture of non-linear polymers is applied to the study of the copolymerization of methyl methacrylate (MMA) with ethylene glycol dimethacrylate (EGDMA). Dynamic predictions of molecular weight distributions, sequence length distributions and mean square radius of gyration are possible before and after gelation. A set of experiments concerning the copolymerization of MMA and EGDMA was carried out in toluene solution at 60 8C for which classic radical kinetics is a good approximation.
The time evolution of key polymer properties was followed using a SEC system with a
refractive index detector coupled with MALLS allowing the determination of absolute
weight average molecular weight and apparent molecular size distributions as well as
z-average radius of gyration. Special focus was given to assess the influence of the
initial amount of cross-linker on the dynamics of the non-linear structure build-up of these products. A kinetic scheme comprising 23 different chemical species and 76 chemical reactions was used in the modeling studies of this chemical system. Most of the kinetic parameters used in the simulations have been collected from previous
studies. For experiments at low monomer conversion (up to about 0.5) a good
agreement between predictions and experimental measurements is observed for
molecular weights and z-average radius of gyration by fitting a small number of
parameters describing gel effect (with a conversion dependent but chain length
independent termination rate parameter) and the relative propagation on pendant
double bonds. However, predicted values of weight-average molecular weights and
z-average radius of gyration before gelation are too low at higher monomer
conversions with non-linear systems. The likely cause is the presence of intramolecular reactions which should not be neglected in these circumstances.FC
Preparation and barrier properties of chitosan-layered silicate nanocomposite films

18th World Forum on Advanced Polymeric Materials, Siegen, Germany, April 07-10, 2010In this study, chitosan nanocomposite films were prepared using a solvent-casting method by incorporation of an organically modified montmorillonite (Cloisite 10A). The effect of filler concentration on the water vapor permeability, oxygen permeability, mechanical and thermal properties of the composite films was evaluated. The structure of nanocomposites and the state of intercalation of the clay were characterized by XRD. The water vapor permeability of pure chitosan films was measured as a function of relative humidity (RH). It was found that the permeability value increased with an increase in RH. The water vapor and gas permeability values of the composite films decreased significantly with increasing filler concentration. Permeation data was fitted to various phenomenological models predicting the permeability of polymer systems filled with nanoclays as a function of clay concentration and aspect ratio of nanoplatelets. According to the XRD results, an increase in basal spacing was obtained with respect to pure clay for chitosan/clay nanocomposites. This demonstrated the formation of intercalated structure of clay in the polymer matrix. Tensile strength and elongation at break of the composites increased significantly with the addition of clay, however the thermal and color properties of the films were not much affected by the intercalation of clay into polymer matrix
A near-infrared spectroscopy study on thermal transitions of PMMA and PMMA/SiO2 nanocomposites

In this work infrared spectroscopy in the near infrared (NIR) range is used to study the dynamics of polymethylmethacrylate (PMMA) as a pure polymer and when it is modified with silica nanoparticles. Different ways of analyzing FT-NIR spectra were explored taking the temperature as the variable of the systems: i) bands shifts in terms of the first moment of the wavenumber; ii) bands shifts in terms of an absorbance ratio method and iii) absorbance variations in terms of the integrated absorbance. The spectroscopic analysis allowed to study thermal transitions in PMMA and PMMA based nanocomposites. In particular the method based on the use of an absorbance ratio is the most sensible to analyze the thermal transitions. All bands considered could be used to detect thermal transitions reflecting how the vibrations of the groups CH2; CH3 and C¼O are affected by changes in the free volume of the PMMA. It seems that the PMMA dynamics is more driven by the lateral groups than the backbone of the polymer. The presence of silica nanoparticles, at least when 1% by weight is used, restrains the PMMA motion increasing the relaxation temperatures that can be associated with the glass transitions
Synthesis of Amphiphilic Three-Armed Star Random Copolymers via Living Radical Polymerization and their Unimolecular Folding Properties in Water

Amphiphilic three-armed star random copolymers were synthesized by ruthenium-catalyzed living radical copolymerization of hydrophilic poly(ethylene glycol) methyl ether methacrylate (PEGMA) and hydrophobic dodecyl methacrylate (DMA). Their amphiphilic star random copolymers with 10-50 mol% DMA efficiently self-folded in water with intramolecular hydrophobic interaction to form compact unimolecular micelles. Owing to PEG segments, star copolymers were thermoresponsive to induce lower critical solution temperature-type phase separation in water