Reactive Matrices Research Articles

2-Nitro-4-Carboxyphenylhydrazine and 2,4-Dicarboxylphenylhydrazine as a Pair of Novel Reactive MALDI Matrices for Rapid and Accurate Profiling of N-Glycome in Dual Ion Modes.

N-glycosylation is closely linked to a wide range of biological functions in organisms. Owing to the constriction of awful crystals formed by conventional MALDI matrices and the extremely inferior ionization efficiency of N-glycans, the traditional direct detection of N-glycans by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been gradually replaced by postderivatization detection using reactive matrices. Nevertheless, the laborious identification of complex spectral peaks remains the major difficulty in N-glycan profiling. Hence, we logically designed and synthesized two novel reactive matrices, 2-nitro-4-carboxylphenylhydrazine (NCPH) and 2,4-dicarboxylphenylhydrazine (DCPH), and separately combined them with the acidic matrix 2,5-dihydroxybenzoic acid (DHB) to constitute two composite matrices with high on-target derivatization efficiency and significant promotion of N-glycan ionization for productive MALDI analysis in dual ion modes. Using both composite matrices, we can actualize MALDI-MS and MS2 mass calibration in dual ion modes by postderivatization detection and fragmentation of dextrans and selectively enhance the ionization effect of oligosaccharides in mixed systems. Quite homogeneous cocrystals can ensure N-glycan quantification with decent linearity and reproducibility. A fixed mass difference derived from the identical N-glycan in two ion modes is available for rapid identification in complex biological samples. Ultimately, the developed strategy was triumphantly employed to identify and quantify the relative content and alteration tendency of peach N-glycans, which can be referable to the latent correlation between N-glycan expression and peach ripening.

Hydrazide-based reactive matrices for the sensitive detection of aldehydes and ketones by MALDI mass spectrometry imaging.

A one-step, on-tissue chemical derivatisation method for MALDI mass spectrometry imaging was found to improve the detectability of aldehydes and ketones by charge-tagging. The developed reactive matrices, containing a UV-chromophore, ionisable moiety and hydrazide group, showed an equal or higher detection efficiency than Girard's reagent P, enabling improved imaging of brain metabolites without the need for additional co-matrices.

Reactive Matrices for MALDI-MS of Cholesterol.

Cholesterol is a critical molecule whose dysregulation in certain brain regions is related to multiple neurological disorders. It is of pathological importance to map the distribution of cholesterol in brain. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been widely used in the molecular imaging of metabolites at a high spatial resolution. However, it is challenging to analyze cholesterol by MALDI-MS due to its difficulty in ionization. Herein, we present for the first time a type of reactive matrix for MALDI-MS of cholesterol. Methylpyridinium carboxaldehydes react with cholesterol and other hydroxyl-containing sterols, which greatly enhanced both desorption and ionization and improved the limits of detection to the low μg/mL range. Compared with previous methods, our reactive matrix requires only one step of chemical derivatization and avoids time-consuming enzymatic reaction, which simplified the sample pretreatment. The reactive matrix was successfully used in mapping the distribution of cholesterol in brain tissue sections using MALDI-MS imaging. In summary, this work has provided a sensitive and simple method for the MALDI-MS analysis of cholesterol, has proposed a novel solution to visualize the distribution of sterol metabolites, and has great potential for applications in neurological and pathological studies.

Emulsification of low viscosity oil in alkali-activated materials

This research aims to understand the mechanisms enhancing the fixation of low viscosity mineral oils, including tailings, in reactive inorganic matrices, by emulsification. To this purpose, significant amounts of a model low viscosity pure mineral oil (20%vol) are immobilized in alkali-activated materials (AAM), either based on metakaolin or blast furnace slag. In such case, Portland cement-based matrices are not adequate (emulsification delicate to manage and excessive setting retardation). Various surfactants are used to ease the oil emulsion.Visual observation and rheology evidence two distinct groups of surfactants. One contributes to structuring the oil/AAM fresh mix, with greater viscosity than without surfactant; the other includes non-structuring surfactants, without change in viscosity. Each group depends on the AAM considered.Whatever the AAM and the surfactant, the oil droplet size decreases significantly, without consistent correlation with the interfacial tension between oil/activating solution (AS). Interfacial tension alone does not explain the reduction in oil droplet size. Characterization of diluted ternary suspensions (solid particles – oil – AS) relates the structuring effect to interactions between oil and solid particles, through the surfactant polar head groups and non-polar hydrocarbon tails. A detailed mechanism explaining the oil stabilization and the mix structuring is discussed.

Tailoring the Hydroxyl Density of Glass Surface for Anionic Ring-Opening Polymerization of Polyamide 6 to Manufacture Thermoplastic Composites.

Reactive thermoplastics matrices offer ease of processing using well-known molding techniques (such as Resin Transfer Molding) due to their initially low viscosity. For Polyamide 6 (PA6)/glass composites, the hydroxyl groups on the glass surface slow down the anionic ring-opening polymerization (AROP) reaction, and can ultimately inhibit it. This work aims to thoroughly control the hydroxyl groups and the surface chemistry of glass particulates to facilitate in situ AROP-an aspect that has been barely explored until now. A model system composed of a PA6 matrix synthesized by AROP is reinforced with calcinated and silanized glass microparticles. We systematically quantify, by TGA and FTIR, the complete particle surface modification sequence, from the dehydration, dehydroxylation and rehydroxylation processes, to the silanization step. Finally, the impact of the particle surface chemistry on the polymerization and crystallization of the PA6/glass composites was quantified by DSC. The results confirm that a careful balance is required between the dehydroxylation process, the simultaneous rehydroxylation and silane grafting, and the residual hydroxyl groups, in order to maintain fast polymerization and crystallization kinetics and to prevent reaction inhibition. Specifically, a hydroxyl concentration above 0.2 mmol OH·g−1 leads to a slowdown of the PA6 polymerization reaction. This reaction can be completely inhibited when the hydroxyl concentration reaches 0.77 mmol OH·g−1 as in the case of fully rehydroxylated particles or pristine raw particles. Furthermore, both the rehydroxylation and silanization processes can be realized simultaneously without any negative impact on the polymerization. This can be achieved with a silanization time of 2 h under the treatment conditions of the study. In this case, the silane agent gradually replaces the regenerated hydroxyls. This work provides a roadmap for the preparation of reinforced reactive thermoplastic materials.

Arrays of Sub-Terahertz Cryogenic Metamaterial

Integrated quasi-optical cryogenic terahertz receivers contain arrays of detectors, quasi-optical filters, interferometers, and other metamaterials. Matrices of quasi-optical band-pass, low-pass, and high-pass filters, Fabry–Perot grid interferometers, and arrays of half-wave and electrically small antennas with superconductor-insulator-normal metal-insulator-superconductor (SINIS) sub-terahertz wavelength range detectors were fabricated and experimentally studied on the same computational, technological, and experimental platform. For the design of the filters, we used the periodic frequency-selective surfaces (FSS) approach, contrary to detector arrays that can be presented in a model of distributed absorbers. The structures were fabricated using direct electron beam lithography, thermal shadow evaporation, lift-off, alternatively magnetron sputtering, and chemical and plasma etching. The numerical simulation methods of such structures are sufficiently different: for the reactive matrices with low losses, the approximation of an infinite structure with periodic boundary conditions is applicable, and for the arrays of detectors with dissipative elements of absorbers, a complete analysis of the finite structure with hundreds of interacting ports is applicable. The difference is determined by the presence of dissipation in the detector arrays, the phase of the reflected or re-emitted signal turned out to be undefined and the Floquet periodic boundary conditions are correct only for a phased array antenna. The spectral characteristics of the created filters, interferometers, and antenna arrays were measured in the frequency range 50–600 GHz.

MALDI Matrices for the Analysis of Low Molecular Weight Compounds: Rational Design, Challenges and Perspectives.

The analysis of low molecular weight (LMW) compounds is of great interest to detect small pharmaceutical drugs rapidly and sensitively, or to trace and understand metabolic pathways. Matrix‐assisted laser desorption/ionization mass spectrometry (MALDI MS) plays a central role in the analysis of high molecular weight (bio)molecules. However, its application for LMW compounds is restricted by spectral interferences in the low m/z region, which are produced by conventional organic matrices. Several strategies regarding sample preparation have been investigated to overcome this problem. A different rationale is centred on developing new matrices which not only meet the fundamental requirements of good absorption and high ionization efficiency, but are also vacuum stable and “MALDI silent”, i. e., do not give matrix‐related signals in the LMW area. This review gives an overview on the rational design strategies used to develop matrix systems for the analysis of LMW compounds, focusing on (i) the modification of well‐known matrices, (ii) the search for high molecular weight matrices, (iii) the development of binary, hybrid and nanomaterial‐based matrices, (iv) the advance of reactive matrices and (v) the progress made regarding matrices for negative or dual polarity mode.

Development and Validation of a Test Mold for Thermoplastic Resin Transfer Molding of Reactive PA-6.

Thermoplastic resin transfer molding (T-RTM) is a cutting-edge manufacturing technique for high-volume production of composites with a recyclable thermoplastic matrix. Although a number of reactive thermoplastic matrices as well as industrial manufacturing equipment for T-RTM are commercially available today, the design of a T-RTM mold is still based on the skills and personal experience of the designer. This study summarizes the best knowledge and expertise in mold design and manufacturing and introduces an innovative mold for T-RTM. A concept and basic principles for designing a T-RTM mold are formulated in this study. The mold developed is manufactured and validated.

3D Freeform Printing of Nanocomposite Hydrogels through in situ Precipitation in Reactive Viscous Fluid

Composite hydrogels have gained great attention as three-dimensional (3D) printing biomaterials because of their enhanced intrinsic mechanical strength and bioactivity compared to pure hydrogels. In most conventional printing methods for composite hydrogels, particles are preloaded in ink before printing, which often reduces the printability of composite ink with little mechanical improvement due to poor particle-hydrogel interaction of physical mixing. In contrast, the in situ incorporation of nanoparticles into a hydrogel during 3D printing achieves uniform distribution of particles with remarkable mechanical reinforcement, while precursors dissolved in inks do not influence the printing process. Herein, we introduced a “printing in liquid” technique coupled with a hybridization process, which allows 3D freeform printing of nanoparticle-reinforced composite hydrogels. A viscoplastic matrix for this printing system provides not only support for printed hydrogel filaments but also chemical reactants to induce various reactions in printed objects for in situ modification. Nanocomposite hydrogel scaffolds were successfully fabricated through this 3D freeform printing of hyaluronic acid (HAc)-alginate (Alg) hydrogel inks through a two-step crosslinking strategy. The first ionic crosslinking of Alg provided structural stability during printing, while the secondary crosslinking of photo-curable HAc improved the mechanical and physiological stability of the nanocomposite hydrogels. For in situ precipitation during 3D printing, phosphate ions were dissolved in the hydrogel ink and calcium ions were added to the viscoplastic matrix. The composite hydrogels demonstrated a significant improvement in mechanical strength, biostability, as well as biological performance compared to pure HAc. Moreover, the multi-material printing of composites with different calcium phosphate contents was achieved by adjusting the ionic concentration of inks. Our method greatly accelerates the 3D printing of various functional or hybridized materials with complex geometries through the design and modification of printing materials coupled with in situ post-printing functionalization and hybridization in reactive viscoplastic matrices.

3D Freeform Printing of Nanocomposite Hydrogels through in situ Precipitation in Reactive Viscous Fluid

Composite hydrogels have gained great attention as three-dimensional (3D) printing biomaterials because of their enhanced intrinsic mechanical strength and bioactivity compared to pure hydrogels. In most conventional printing methods for composite hydrogels, particles are preloaded in ink before printing, which often reduces the printability of composite ink with little mechanical improvement due to poor particle-hydrogel interaction of physical mixing. In contrast, the in situ incorporation of nanoparticles into a hydrogel during 3D printing achieves uniform distribution of particles with remarkable mechanical reinforcement, while precursors dissolved in inks do not influence the printing process. Herein, we introduced a “printing in liquid” technique coupled with a hybridization process, which allows 3D freeform printing of nanoparticle-reinforced composite hydrogels. A viscoplastic matrix for this printing system provides not only support for printed hydrogel filaments but also chemical reactants to induce various reactions in printed objects for in situ modification. Nanocomposite hydrogel scaffolds were successfully fabricated through this 3D freeform printing of hyaluronic acid (HAc)-alginate (Alg) hydrogel inks through a two-step crosslinking strategy. The first ionic crosslinking of Alg provided structural stability during printing, while the secondary crosslinking of photo-curable HAc improved the mechanical and physiological stability of the nanocomposite hydrogels. For in situ precipitation during 3D printing, phosphate ions were dissolved in the hydrogel ink and calcium ions were added to the viscoplastic matrix. The composite hydrogels demonstrated a significant improvement in mechanical strength, biostability, as well as biological performance compared to pure HAc. Moreover, the multi-material printing of composites with different calcium phosphate contents was achieved by adjusting the ionic concentration of inks. Our method greatly accelerates the 3D printing of various functional or hybridized materials with complex geometries through the design and modification of printing materials coupled with in situ post-printing functionalization and hybridization in reactive viscoplastic matrices.

Flavor stability assessment of lager beer: what we can learn by comparing established methods

Beer is prone to flavor changes during aging that influence consumer acceptance within shelf life. The shelf life of beer is defined as the period over which flavor changes remain acceptable. Assessment of flavor changes caused by volatiles is typically achieved with a combination of sensory evaluation and gas chromatography–mass spectrometry (GC–MS). Volatile indicators causing flavor changes during beer aging are commonly determined with headspace solid–phase microextraction (HS-SPME), solvent-assisted flavor evaporation (SAFE), or steam distillation (SD). However, discrepancies occur when comparing results from different analytical methods that affect the assessment of the degree of flavor stability. This article discusses the effect of different established analytical methods on flavor stability assessment. Reaction potentials of de novo formation, release from adducts, and degradation are hypothesized to participate in the observed discrepancies, and evidence is verified using model systems. Three extraction methods were qualitatively compared by multiple gas chromatography–olfactometry experiments (GC–O) of a one-year, naturally aged, pale lager beer. SD showed the highest number of detected aroma compounds (41), followed by HS-SPME (33), and SAFE (26). Aroma intensities for SD were more pronounced for most aging indicators than with other methods. With SAFE, only 11 aging compounds could be identified confidently, with weak aroma intensities at GC–O, and this method was thereby excluded from further experiments. Certain aging compounds were calibrated for gas chromatography-mass spectrometry (GC–MS) from HS-SPME and SD, although most compounds were present at the lower limits of detection and quantification. Relative standard deviation and recoveries for all compounds were acceptable for both methods. Quantitative comparison was conducted for four different commercial pale lager beers at different stages of aging at 20 °C (fresh, 5 months, 10 months). Aging-related changes of pale lager beer presented with altered profiles and behavior in SD compared to the non-invasive HS-SPME due to heat intake, and were borne out by GC–O results. Model systems were used to describe the impact of isolated aging-relevant mechanisms and precursors during distillation. Our findings suggest that results from different methods in reactive matrices should be compared cautiously, especially regarding aroma activity, and indicate that the most gentle or non-invasive method should be applied for analysis.

Detection of a High-Turnover Serotonin Circuit in the Mouse Brain Using Mass Spectrometry Imaging.

SummaryMonoamine neurotransmitters are released by specialized neurons regulating behavioral, motor, and cognitive functions. Although the localization of monoaminergic neurons in the brain is well known, the distribution and kinetics of monoamines remain unclear. Here, we generated a murine brain atlas of serotonin (5-HT), dopamine (DA), and norepinephrine (NE) levels using mass spectrometry imaging (MSI). We found several nuclei rich in both 5-HT and a catecholamine (DA or NE) and identified the paraventricular nucleus of the thalamus (PVT), where 5-HT and NE are co-localized. The analysis of 5-HT fluctuations in response to acute tryptophan depletion and infusion of isotope-labeled tryptophan in vivo revealed a close kinetic association between the raphe nuclei, PVT, and amygdala but not the other nuclei. Our findings imply the existence of a highly dynamic 5-HT-mediated raphe to PVT pathway that likely plays a role in the brain monoamine system.

Comprehensive mapping of neurotransmitter networks by MALDI-MS imaging.

We present a mass spectrometry imaging (MSI) approach for the comprehensive mapping of neurotransmitter networks in specific brain regions. Our fluoromethylpyridinium-based reactive matrices facilitate the covalent charge-tagging of molecules containing phenolic hydroxyl and/or primary or secondary amine groups, including dopaminergic and serotonergic neurotransmitters and their associated metabolites. These matrices improved the matrix-assisted laser desorption/ionization (MALDI)-MSI detection limit toward low-abundance neurotransmitters and facilitated the simultaneous imaging of neurotransmitters in fine structures of the brain at a lateral resolution of 10 µm. We demonstrate strategies for the identification of unknown molecular species using the innate chemoselectivity of the reactive matrices and the unique isotopic pattern of a brominated reactive matrix. We illustrate the capabilities of the developed method on Parkinsonian brain samples from human post-mortem tissue and animal models. The direct imaging of neurotransmitter systems provides a method for exploring how various neurological diseases affect specific brain regions through neurotransmitter modulation.

Persistent Organic High-Spin Trinitrenes.

The septet ground state trinitrenes 1,3,5‐trichloro‐2,4,6‐trinitrenobenzene and 1,3,5‐tribromo‐2,4,6‐trinitrenobenzene were isolated in inert (Ar, Ne, and Xe) as well as reactive matrices (H2, O2, and H2O) at cryogenic temperatures. These trinitrenes were obtained in high yields by UV photolysis of the corresponding triazides and characterized by IR and UV/Vis spectroscopy. The trinitrenes, despite bearing six unpaired electrons, are remarkably unreactive towards molecular oxygen and hydrogen and are persistent in water ice up to 160 K where the water matrix starts to sublime off.

Persistent Organic High‐Spin Trinitrenes

AbstractThe septet ground state trinitrenes 1,3,5‐trichloro‐2,4,6‐trinitrenobenzene and 1,3,5‐tribromo‐2,4,6‐trinitrenobenzene were isolated in inert (Ar, Ne, and Xe) as well as reactive matrices (H2, O2, and H2O) at cryogenic temperatures. These trinitrenes were obtained in high yields by UV photolysis of the corresponding triazides and characterized by IR and UV/Vis spectroscopy. The trinitrenes, despite bearing six unpaired electrons, are remarkably unreactive towards molecular oxygen and hydrogen and are persistent in water ice up to 160 K where the water matrix starts to sublime off.

Combination Strategy of Reactive and Catalytic Matrices for Qualitative and Quantitative Profiling of N-Glycans in MALDI-MS.

Qualitative and quantitative analysis of N-glycans by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is hampered mainly by the low ionization efficiency of analytes and their poor cocrystallization with traditional organic acid matrices. In the present study, a combination strategy of reactive and catalytic matrices (CSRCM) was proposed for the on-target derivatization and detection of reducing N-glycans: a novel reactive matrix, i.e., 2,5-dihydroxybenzohydrazide (DHBH), having a skeleton structure similar to that of DHB, was designed and synthesized, and this reactive matrix was mixed with catalytic matrix DHB to form a rationally combinatorial matrix (DHB/DHBH). Qualitatively, DHB/DHBH could improve the ionization efficiency of reducing carbohydrates significantly. Quantitatively, the acid-base chemistry of DHB/DHBH leads to a uniform cocrystallization of analytes-matrix mixtures. Consequently, CSRCM provides accurate quantitation for N-glycans with high derivatization efficiency and good linearity (R2 > 0.99) within 2 orders of magnitude on the basis of an internal standard method. Furthermore, the CSRCM was successfully applied to evaluating N-glycan in serum samples of colorectal cancer patients, thus showing potential in clinical applications for biomarker discovery.

Effects of correlated morphological and topological heterogeneity of pore network on effective transport and reaction parameters

The effective diffusivity and the effective Thiele modulus of reactive porous matrices are determined by using a hybrid discrete and continuum model. The model describes static heterogeneity with weak noise on both morphology and topology of the matrix. Variations in diffusivity with respect to pore size (radius and length) and network connectivity up to second order are analyzed to assess the effect of stochastic media on catalytic reaction and transition of a single species. The porous medium is simulated by several building blocks (BB) which are regular in topology and morphology. A methodology is presented to construct a BB such that it fits the true matrix. Permutation of several regular pore networks in series constructs the porous media. Local mass balances over each BB yields model equations for reaction and transport in the matrix. Correlated random walk theory is used in each BB in order to relate the diffusivity to the coordination number.The Gaussian correlation function is assumed to model the autocorrelation of independent variables which are used to characterize the correlated porous media. The contribution of the fluctuating parameters in the mass conservation of the matrix yields a new closure equation in which ensemble average concentration of the reactant depends on different cross-correlations. The model is stable as long as the Thiele modulus at the correlation length scale is small. It predicts that geometrical heterogeneities lead to correction in effective diffusivity while the reaction rate is unaffected due to small Thiele modulus at correlation length scale. The model is verified by assessing the Thiele modulus of a pore network under Knudsen regime during a first order catalytic reaction; a good agreement was found especially for moderate Thiele modulus of correlated network. However, it fails to simulate random networks. Our systematic study revealed that the pore radius statistics impact significantly the diffusivity and the Thiele modulus while the topological parameters are important in weakly connected networks. The model predictions show that the diffusion constant decreases sharply as pore radius variance increases but increases smoothly with Thiele modulus.

Flexural characteristics of novel carbon methylmethacrylate composites

Abstract Reactive thermoplastic matrices are widely used for polymer composites manufacturing owing to their ease of processing using cost-effective liquid injection processes. The novel methyl methacrylate (MMA) Elium ® resin is a liquid thermoplastic resin, first of its kind which is curable at room temperature. It has attracted wide interest as a competitive solution to epoxy-based composites for structural applications. In this work, the flexural performances of novel non-crimp carbon fabric (NCCF) Elium® composite laminates are evaluated. The baseline comparison is done with conventionally used composites with epoxy resin. The stress-strain curve, the fracture failure mechanisms and the effect of the annealing stage have been discussed.

Novel Reactive Matrices for the Analysis of Alcohols by Matrix-Assisted Laser Desorption/Ioization Mass Spectrometry

A possibility of using a number of aromatic and heteroaromatic carboxylic acids and their halogen anhydrides as reactive matrix compounds for the analysis of alcohols of different structures by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry has been studied. It is shown that the acylation of alcohols with nicotinic and quinoline-6-carboxylic acid chlorides gives derivatives with high desorption/ionization efficiency under MALDI conditions, and that the free acids formed as a result of the hydrolysis of anhydrides act as matrix compounds. The proposed approach is tested on a number of aliphatic, alicyclic, and aromatic alcohols.

Reaction: Exploring the Chemistry Frontier in Water-Borne Vessels

In 2007, John Warner and Jim Babcock founded the Warner Babcock Institute for Green Chemistry and, with Amy Cannon, founded the green chemistry education nonprofit organization Beyond Benign. John is the recipient of the 2004 Presidential Award for Excellence in Science Mentoring and the 2014 Perkin Medal. In addition, John is one of the founders of the field of green chemistry and is co-author of the defining textbook Green Chemistry: Theory and Practice. In 2017, the German Ministry of Economic Affairs and the Technische Universitat Berlin announced the naming of the John Warner Center for Green Chemistry Start-Ups in his honor.