MS Measurements Research Articles

Application of portable gas chromatography–mass spectrometer for rapid field based determination of TCE in soil vapour and groundwater

The application of portable chromatography–mass spectrometer (GC–MS) is restrained by its detection limits without the development of proper sample pre-concentration methods. The primary focus of this paper is to introduce a practical field measurement methodology for the analysis of volatile organic compounds (VOCs) in soil vapour and groundwater using a portable gas (GC–MS)system for application to in situ assessment of vapour intrusion from VOC contamination. A solid-phase micro-extraction (SPME) technique was applied for sample pre-concentration before the GC–MS​ measurement. Practical in-field soil gas SPME sampling methods have been developed to optimise the SPME extraction efficiency to then ultimately improve the detection limits of portable GC–MS. An Australian site impacted by a chlorinated VOC, trichloroethylene (TCE), was the subject of the case study. To rapidly assess soil vapour samples in subsurface soil, in-house-developed retractable soil vapour sampling probes (SVSPs) were installed at the site in clusters at depths of 1 m, 2 m and 3 m below ground level at each sampling location. Use of the SVSPs for sampling enabled the generation of a three-dimensional map and distribution contours for TCE concentrations using the in situ measurement results of a portable GC–MS analysis for vapour intrusion investigation. The results of the portable GC–MS​ analysis were compared with the results from conventional USEPA methods, such as TO-15 and Method 8265 for soil vapour and groundwater samples, respectively. This work demonstrates that the developed methodology of using a portable GC–MS system has the capability for in-field quantitative analysis of VOCs for rapid contaminated site vapour intrusion assessment.

Amyloid β aggregation inhibitory activity of triterpene saponins from the cactus Stenocereus pruinosus.

Six new triterpene saponins (1–5,7) and 3 known saponins (6,8,9) were isolated from MeOH extracts of the cactus Stenocereus pruinosus. The structures of the isolated saponins were elucidated using MS, IR, and comprehensive NMR measurements. To develop drugs for treating Alzheimer’s disease (AD) on the basis of the amyloid cascade hypothesis, the isolated saponins were evaluated for inhibition of BACE1 activity and amyloid beta (Aβ) aggregation using thioflavin-T assay, and triterpenes as an aglycone moiety and an alkaline hydrolysate of the saponins were also evaluated. One saponin, stenoside A (7), exhibited inhibitory activity related to Aβ aggregation and its degree of Aβ aggregation was 40.6% at 100 μM.Graphic abstract Electronic supplementary materialThe online version of this article (10.1007/s11418-020-01463-0) contains supplementary material, which is available to authorized users.

Effects of Secondary Sources of Underground Nuclear Explosions on the mb : Ms Criterion and Implications for Discrimination of the DPRK’s Nuclear Tests

ABSTRACTThe mb : Ms (mb vs. Ms) relationship is an important criterion for screening explosions from earthquakes and has been widely adopted in seismological monitoring by the Comprehensive Nuclear-Test-Ban Treaty Organization. In general, the earthquakes have larger Ms than the underground explosions with equivalent mb. However, it has been reported that this recognition criterion failed to identify some explosions at the North Korea nuclear test site. In this study, we investigate the potential effects of secondary source components, including the compensated linear vector dipole (CLVD) and double-couple (DC) sources, on mb and Ms magnitude measurements and the physical mechanism of the mb : Ms recognition criterion by calculating synthetic seismograms. The results show an apparent critical body-wave magnitude of 5 when using the mb : Ms method to discriminate North Korean underground nuclear explosions. The Ms measurements decrease as the CLVD components increase, whereas the effects from the DC source can be neglected. Small events, such as the first five North Korean nuclear tests, generate weak CLVD components, leading to the failure of mb : Ms-based discrimination, whereas the last event, with a larger magnitude, caused extensive damage and hence can be successfully discriminated. In addition, the large difference between the source spectrum of explosions and those of earthquakes might be another important factor in the successful mb : Ms-based discrimination of the sixth North Korean nuclear test.

Optimisation of the use of sliding window deconvolution for comprehensive characterisation of trastuzumab and adalimumab charge variants by native high resolution mass spectrometry

The biopharmaceutical industry continues to develop mAb-based biotherapeutics in increasing numbers. Due to their complexity, there are several critical quality attributes (CQAs) that need to be measured and controlled to guarantee product safety and efficacy. Charge variant analysis is a widely used method to monitor changes in product quality during the manufacturing process of monoclonal antibodies (mAbs) and, together with a bottom-up peptide centred approach, acts as a key analytical platform to fulfil regulatory requirements. Native MS measures biomolecules under conditions that preserve most aspects of protein tertiary and quaternary structure, enabling direct characterization of large intact proteins such as mAbs. The resulting native mass spectrum of a mAb is characterized by a narrower charge-state envelope that simplifies the spectra and also condenses the ion signals into fewer peaks, increasing the signal-to-noise ratio. Algorithmic spectral deconvolution is needed for routine accurate and rapid molecular weight determination, and consequently, multiple deconvolution algorithms have evolved over the past decade. Here, we demonstrate the utility of the sliding window algorithm as a robust and powerful deconvolution tool for comprehensive characterisation of charge variant analysis data for mAbs. Optimum performance is evaluated by studying the impact of critical software parameters on detection, identification and relative quantitation of protein isoforms. By combining molecular mass and retention time information, it was possible to identify multiple modifications on adalimumab and trastuzumab, both IgG1 mAbs, including lysine truncation, deamidation and succinimide formation, along with the N-glycan distribution of each of the identified charge variants. Sliding window deconvolution also provides a key benefit of low abundant variant detection in a single analysis and the ability to detect co-eluting components with different relative abundances. The studied mAbs demonstrate the algoritms applicability for efficient data processing of both simple and complex mAbs analysed using pH gradient cation exchange chromatography coupled to native mass spectrometry.

A Python-Based Pipeline for Preprocessing LC-MS Data for Untargeted Metabolomics Workflows.

Preprocessing data in a reproducible and robust way is one of the current challenges in untargeted metabolomics workflows. Data curation in liquid chromatography–mass spectrometry (LC–MS) involves the removal of biologically non-relevant features (retention time, m/z pairs) to retain only high-quality data for subsequent analysis and interpretation. The present work introduces TidyMS, a package for the Python programming language for preprocessing LC–MS data for quality control (QC) procedures in untargeted metabolomics workflows. It is a versatile strategy that can be customized or fit for purpose according to the specific metabolomics application. It allows performing quality control procedures to ensure accuracy and reliability in LC–MS measurements, and it allows preprocessing metabolomics data to obtain cleaned matrices for subsequent statistical analysis. The capabilities of the package are shown with pipelines for an LC–MS system suitability check, system conditioning, signal drift evaluation, and data curation. These applications were implemented to preprocess data corresponding to a new suite of candidate plasma reference materials developed by the National Institute of Standards and Technology (NIST; hypertriglyceridemic, diabetic, and African-American plasma pools) to be used in untargeted metabolomics studies in addition to NIST SRM 1950 Metabolites in Frozen Human Plasma. The package offers a rapid and reproducible workflow that can be used in an automated or semi-automated fashion, and it is an open and free tool available to all users.

260 kHz mode-spacing optical frequency combs for scan-free high-resolution direct-comb spectroscopy

For scan-free high-resolution direct-comb spectroscopy, mode spacing of an optical frequency comb is reduced down to 260 kHz by phase modulation. It turns out that time-domain signal is degraded by averaging because of slow optical path length fluctuations and fast optical pulse timing jitter. In this study, compensation of these effects is introduced, and signal degradation by averaging is avoided. With demonstrations of direct-comb spectroscopy with the narrow-mode-spacing optical frequency comb, Doppler-limited absorption spectrum of methane and reflection spectrum from an optical ring cavity are observed. As a result, detailed resonance spectral line profile of 8 MHz linewidth for the optical ring cavity is obtained in 50 ms measurement time.

Constituents of Bupleurum praealtum and Bupleurum veronense with Potential Immunomodulatory Activity.

In this investigation, chromatographic separations of the diethyl ether extracts of two European annual Bupleurum taxa, B. praealtum and B. veronense, yielded nine new natural products, namely, a series of esters of stereoisomeric tetradeca-5,7,9,11-tetraen-1-ols (1-4 and 8), a tetra-unsaturated γ-tetradecalactone (5), a dibenzylbutyrolactone lignan (7-oxoarcitin, 6), a falcarinol-related 17-membered macrolide (7) possessing a conjugated diyne-system, and an acylphloroglucinol derivative (9). All these new compounds were fully characterized by NMR, IR, UV, MS, and optical rotation measurement, including 1H NMR full spin spectral simulation, whereas the absolute configurations of 1, 5, and 9 were determined via chemical correlations and NMR analysis of Mosher esters. The in vitro potential immunomodulatory activities of 1, 4, 5, and (+)-arcitin were assessed by determining their effects on the functional properties of isolated rat splenocytes and peritoneal macrophages. The results obtained support the known immunomodulatory ethnomedicinal usage of Bupleurum species.

10.4314/bcse.v25i2.65886

A multidentate ligand, 3,4-bis(2-iminomethylphenol)-2,2’:5,2’’-terthiophene (L), has been synthesized by the condensation of 3,4-diamino-2,2’:5,2’’-terthiophene and salicylaldehyde. The ligand and Ni(II) and Zn(II) complexes were synthesized and characterized by IR, NMR, UV-Vis, AAS, MS, molar conductivity and magnetic susceptibility measurements. The ligand behaves as neutral ONS-ONS bis-chelant towards Ni(II) in [Ni 2 LCl 4 (H 2 O) 2 ]×4H 2 O and as dibasic ONNO donor towards Zn(II) in [ZnL(NH 3 ) 2 ]. The dinuclear Ni(II) complex exhibits subnormal magnetic moment at room temperature due to metal-metal interaction through extended conjugation. The participation of the ring sulfur in bonding towards Ni(II) and the non-participation of the same towards Zn(II) are notable features. Octahedral geometries are proposed for both complexes. Cyclic voltammetric studies revealed electrochemical polymerization of the free ligand (L) but not of the Ni(II) and Zn(II) complexes. KEY WORDS : Variable denticity, 3,4-bis(2-Iminomethylphenol)-2,2’:5,2’’-terthiophene, Octahedral, Ni(II) complex, Zn(II) complex, Voltammetric studies Bull. Chem. Soc. Ethiop. 2011 , 25(2), 221-231.

Aom2 S: A new web-based application for DNA/RNA tandem mass spectrometry data interpretation.

The Analysis of Oligonucleotide Modifications from Mass Spectra (Aom2 S) was created to support the analysis of oligonucleotide mass spectra. This application complements the existing software tools by providing a comprehensive analysis of oligonucleotide fragments from high-resolution tandem mass spectrometry (HR-MS/MS) data in a flexible and user-friendly manner, directly accessible through a web browser without any need for installation. MS measurements of aminoC6-DNA and inosine-RNA were performed using an LTQ Orbitrap FT-MS instrument. The obtained data were analyzed by our newly developed open-source package Aom2 S accessible from the ms.epfl.ch web page or directly at https://mstools.epfl.ch/am2s/ to demonstrate the various functionalities of this tool, notably the possibility to identify different product ions from a nucleotide sequence with any fixed/variable modification by matching theoretical isotopic patterns to any experimental mass spectra with similarity scores ranking. A detailed description of the Aom2 S tool with its user-friendly interface is exemplified using HR-MS/MS data of modified DNA and RNA oligonucleotides. Explanations of analysis parameters and tool workflow, as well as multiple options for viewing and exporting the results, are provided. Product ion assignment and modification localization can be achieved in seconds, and results can be exported as tables, matched mass spectra, and fragmentation maps. A new open source tool (Aom2 S) for the analysis of HR-MS/MS data for modified DNA and RNA oligonucleotides is described. Aom2 S is fast, highly flexible, and versatile, allowing automatic precursor and product ion assignment in a comprehensive manner, including internal fragments and variable modification localization, with clear graphical representation of the results.

Synthesis, characterization, thermal properties and biological activity of diazine-ring containing hydrazones and their metal complexes

New coordination compounds have been synthesized by reacting Zn(II) and Co(II) nitrate or acetate in the presence of triethylamine with Schiff-base ligands containing diazine-ring, pyridine-2-carbaldehyde phthalazine-1-hydrazone, HzPYH, and di(2-pyridyl)ketone 3-chloro-pyridazine-6-hydrazone, HpDPKH. Complexes of [Co(HzPY)2]·3.4H2O, [Zn(HzPY)2] and [Co(HpDPK)2]NO3·H2O were obtained. The crystal and the molecular structure of [Co(HzPY)2]·3.4H2O were determined using X-ray diffraction structure analysis. The compounds were characterized by elemental analysis, FT-IR and UV–Vis spectral data, conductivity and magnetic measurements, too. Except for the diamagnetic Co(III) compound with a nitrate counter-ion, [Co(HpDPK)2]NO3·H2O, all the complexes are neutral-type. The magnetic moment of [Co(HzPY)2]·3.4H2O indicated a low-spin octahedral complex which is relatively rear amongst octahedral Co(II) complexes. Hence, its magnetic moment was measured in the temperature range of 3–300 K. To obtain products in the form of single crystals and/or to increase the yield, the reactions were carried out in solutions with different solvents or recrystallized from solvent mixtures. To determine the nature of the solvent (if any) in the crystalline products and to gain better insight into the decomposition mechanism, coupled TG–MS measurements were carried out. The desolvated compounds were stable at relatively high temperatures (> 200 °C). The cytotoxic, antiproliferative and efflux pump inhibitory effects of the compounds were tested in multidrug-resistant mouse T-lymphoma cells to study their effect on the suppression of MDR. The antibacterial activity of the compounds was also tested. The results of the antibacterial tests were analysed to understand better the effect of the central atoms and the structure on a specific activity.

Computational assessment of the feasibility of protonation-based protein sequencing.

Recent advances in DNA sequencing methods revolutionized biology by providing highly accurate reads, with high throughput or high read length. These read data are being used in many biological and medical applications. Modern DNA sequencing methods have no equivalent in protein sequencing, severely limiting the widespread application of protein data. Recently, several optical protein sequencing methods have been proposed that rely on the fluorescent labeling of amino acids. Here, we introduce the reprotonation-deprotonation protein sequencing method. Unlike other methods, this proposed technique relies on the measurement of an electrical signal and requires no fluorescent labeling. In reprotonation-deprotonation protein sequencing, the terminal amino acid is identified through its unique protonation signal, and by repeatedly cleaving the terminal amino acids one-by-one, each amino acid in the peptide is measured. By means of simulations, we show that, given a reference database of known proteins, reprotonation-deprotonation sequencing has the potential to correctly identify proteins in a sample. Our simulations provide target values for the signal-to-noise ratios that sensor devices need to attain in order to detect reprotonation-deprotonation events, as well as suitable pH values and required measurement times per amino acid. For instance, an SNR of 10 is required for a 61.71% proteome recovery rate with 100 ms measurement time per amino acid.

The Effect of Severe Plastic Deformation on the Corrosion Resistance of AISI Type 304L Stainless Steel

The AISI type 304L stainless steel (SS) was solution annealed at 1050 °C and cryo-rolled at liquid nitrogen (L-N2) temperature (77 K) under severe plastic deformation (SPD). The thickness reduction through cryo-rolling plastic deformation was carried out up to 90% (designated as CR-90) of initial thickness. The cryo-rolling during rolling at liquid N2 temperature (77 K), resulted in transformation induced plastic deformation of the austenite γ-phase into α’- martensite phase. The phase transformation was characterized by x-ray diffraction (XRD) and saturation magnetization (Ms) measurement. The microstructure was measured by using optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD peak positions confirmed the martensite (α’) phase formation. Saturation magnetization (Ms) value of the cryo-rolled specimens shows increasing linearity with cryo-rolling, and transformed to bct martensite (α’). The measured corrosion rate of the cryo-rolled specimens as per ASTM A-262 practice-C test (Huey test) ranges from 6.6 mpy or 0.167 mm/yr (CR 0) to 12.9 mpy or 0.328 mm/yr (CR 90), indicating the effects of severe deformation of strain-induced martensite with the cryo-rolling. Further, the role of severe deformation of strain-induced martensite with the cryo-rolling on AISI type 304L SS and also influence on the corrosion resistance are investigated in detail. The deformation microstructure roles, i.e., the phases and volume percentage induced by the different percentage of the cryo-rolling that influences the corrosion resistance properties and corresponding corrosion resistance in nitric acid have been investigated.

Soot formation in laminar flames of ethylene/ammonia

Co-firing NH3 with other fuels is receiving growing interest as a feasible solution to improve its combustion and emission properties. Previous studies mainly focused on NOx emission, and paid less attention to soot formation which is investigated here using a laminar counterflow flame configuration with ethylene fuel (75% by mole) mixed with different proportions of ammonia (between 0 and 25% by mole while the remainder is nitrogen). Soot volume fraction (SVF) was measured using planar laser induced incandescence (PLII). It was found that the addition of ammonia significantly reduced the measured SVF by 4–6% per 1% ammonia addition as compared to the reference flame (25% nitrogen). To rule out temperature effects, the experiments were simulated using Chemkin Pro and it was found that there were negligible differences in temperature between each condition implying that temperature was not responsible for the reduction in SVF. To investigate the chemical effects of ammonia addition, polycyclic aromatic hydrocarbons (PAH) were measured using planar laser induced fluorescence (PLIF) at 4 wavelengths (350 nm, 400 nm, 450 nm, and 500 nm). PLIF intensities at 350 nm is deemed to correlate with PAHs of 2–3 rings and measured profiles at this wavelength were nearly overlapping for all cases. These findings were supported by GC–MS measurements of acetylene and benzene with the latter showing little change in the peak for the cases studied here. At longer wavelengths, PLIF intensities began to show the same trends found for SVF measurements. Additionally, a specific nitrogen detector was used during GC–MS measurements and several nitrogen containing hydrocarbon species were detected with the 25% addition of ammonia. The combined results indicate that the nitrogen containing hydrocarbon species are likely to account for soot reduction, with the precise mechanism yet to be elucidated.

Structural Analysis of Neutral Nitrogen Compounds Refractory to the Hydrodenitrogenation Process of Heavy Oil Fractions by High-Resolution Tandem Mass Spectrometry and Ion Mobility–Mass Spectrometry

This study aims to identify and characterize compounds refractory to hydrodenitrogenation (HDN). The efficiency of a vacuum hydrocracking unit in removing nitrogen-containing compounds to produce a low-nitrogen-content effluent is examined. Molecular, structural, and compositional knowledge is a requisite for the optimization development of the hydrotreatment step processing unit because changes in the chemical composition of petroleum have a direct impact on physical properties and, thus, overall vacuum gas oil (VGO) upgrading processes. Two samples, a VGO and a effluent obtained after the HDN process containing 10 wppm of N, were analyzed by negative-mode electrospray ionization ultra-high-resolution tandem mass spectrometry (ESI–FT-ICR) and ion mobility spectrometry–mass spectrometry (IMS–MS). FT-ICR mass spectrometry provides ultrahigh mass resolving power to separate and characterize compounds in the highly complex petroleum samples. The fragments generated by MS/MS of selected N₁ refractory compounds were used for structural elucidation. Species with a double bond equivalent of 10 and 13, which proved to be highly refractory, were analyzed in more detail. On the other hand, the TWIMS–TOF MS measurements enabled the entire ion mobility analysis of refractory species to hydrotreatment processes. The MS/MS spectra revealed a specific pattern allowing for the identification of the molecular nucleus. Furthermore, it allowed for the understanding of the fragmentation pathways: loss of alkyl chains in the first step and opening and rearrangement of the nuclei after that. Ion mobility separation, in combination with MS/MS, allowed for the identification of the different conformations and the revealment of the typical fragments of these molecular nuclei. In particular, the ion mobility peak width indicates isomeric diversity and collision cross section (CCS) determination and provides structural information. The IMS analysis of the identified refractory precursor shows the evolution of its compounds at different processing stages and indicates that some families and structural conformations of N₁ species are more resistant to hydrotreatment. Isomers presenting low CCS values in negative mode are more resistant to HDN processes. The combination of TWIMS–TOF MS and ultra-high-resolution mass spectrometry opens exciting and promising prospects for structural determination of complex mixtures, in particular, problematic compounds in petroleum refining processes.

Three dimensional polyvinyl alcohol scaffolds modified with collagen for HepG2 cell culture.

The creation of in vitro functional hepatic tissue simulating micro environmental niche of the native liver is a keen area of research due to its demand in bioartificial liver. However, it is still unclear how to maintain benign cell function while achieving the sufficient cell quantity. In this work, we aim to prepare a novel scaffold for the culture of HepG2 cells, a liver cell line, by modifying polyvinyl alcohol (PVA) scaffold with collagen (COL). PVA is a kind of synthetic biostable polymer with high hydrophilicity in the human body, has been widely used in the biomedical field. However, the use of PVA is limited in cell cultures due to lack of biologically active functional groups. In this study, amino silane (KH-550), glutaraldehyde and native type I collagen were used to modify three-dimensional PVA scaffold to establish a suitable composite scaffold for hepatocyte culture. Three types of composite scaffolds were prepared for different collagen content, named as PVA/COL (0.2%), PVA/COL (0.5%) and PVA/COL (0.8%), respectively. The composite scaffolds were characterized by SEM, XPS, FTIR, MS, porosity estimation and water contact angle measurement. The PVA/COL (0.8%) scaffolds had the highest collagen content of 12.13%. The composite scaffold showed high porosity with interconnected pores. Furthermore, the biocompatibility between HepG2 cells and scaffolds was evaluated by the ability of cell proliferation, albumin secretion, as well as urea synthesis. The coating of collagen on PVA scaffolds promoted hydrophilicity and HepG2 cell adhesion. Additionally, enhanced cell proliferation, increased albumin secretion and urea synthesis were observed in HepG2 cells growing on collagen-coated three-dimensional PVA scaffolds.

Processing of dissolved organic matter from surface waters to sediment pore waters in a temperate coastal wetland

Coastal wetlands are active transitional ecotones between land and ocean, and are considered as hot spots of organic matter processing within the global carbon cycle, which dissolved organic matter (DOM) plays a critical role. In this study, combined use of ultrahigh-resolution mass spectrometry (FT-ICR MS) and complementary optical techniques was conducted to assess the detailed molecular composition of DOM in the temperate Liaohe coastal wetland (LCW), NE China in respect to the differences in DOM composition from surface water to sediment pore water. Significant positive correlations between salinity and dissolved organic carbon (DOC) concentrations were observed in both surface waters and pore waters. Pore water DOM is generally characterized by lower protein-like fluorescence and biological index, but higher humification and humic-like fluorescent components than those in surface water DOM. Corresponding to the optical properties, FT-ICR MS measurements show that pore water DOM has higher proportions of heteroatoms, aromaticity index, O/C ratios, unsaturated aliphatics, and peptides, but lower average H/C ratios compared to surface water DOM across locations with different marsh plant species (rice (Oryza sativa), reed (Phragmites australis), Seablite (Suaeda Salsa)) and salinity (0.5 to 51.5 psu). The results suggest that selective preservation for polyphenols, lignin degradation intermediates (highly unsaturated compounds), and microbial resynthesis of heteroatomic compounds are involved in the processing of DOM from surface water to pore water, leading to the formation of higher molecular weight and sulfur-containing molecules. The abundant CHOS compounds could be related to the early diagenetic sulfurization of DOM in sediments. Our unique data set should provide new clues for a comprehensive understanding of the molecular dynamics of DOM in coastal wetlands.

Stability and structural aspects of complexes forming between aluminum(III) and D-heptagluconate in acidic to strongly alkaline media: An unexpected diversity

In the current contribution, the complex formation equilibria between Al3+ and α-D–heptagluconate (Hpgl−) ions, which is of relevance in, e.g., the Bayer process for obtaining alumina from bauxitic ores, has been investigated. Potentiometric titrations and polarimetric measurements performed at 25 °C and 4 M ionic strength uncovered the formation of several complexes forming in the hyperalkaline (pH ≥ 13) pH range: Al(OH)4Hpgl2−, Al(OH)5Hpgl3−, Al(OH)5Hpgl42−, Al3(OH)13Hpgl62− and Al4(OH)15Hpgl63−. NMR spectroscopy measurements revealed that diverse complexation processes took place in the hyperalkaline region. In the 9 to 7 pH range, ligand–stabilized aluminum hydroxides were formed. In acidic medium, the binding sites of the ligand could be identified as C2H(OH), C3H(OH), C4H(OH) and C5H(OH). Freezing point depression (FPD) measurements indicated, that association occurred to a large extent. ESI–MS measurements confirmed the predominant formation of Al2(OH)6Hpgl− at pH = 7, and implied the coordination via the carboxylate and the adjacent OH functional groups of the ligand.

Nitrile N-oxide-terminated poly(γ-benzyl l-glutamate) (PBLG): synthesis and catalyst-free grafting onto polybutadiene (PBD) and natural rubber (NR)

A nitrile N-oxide-functionalized polypeptide was synthesized by a two-step method involving the combination of ring-opening polymerization of an α-amino acid N-carboxyanhydride monomer using a primary amine initiator containing a nitroalkane group and a subsequent terminal conversion. The catalyst-free grafting reaction of the formed functionalized peptide with rubbers containing double bonds was achieved with high efficiency. A nitrile N-oxide-functionalized polypeptide was synthesized by a two-step method involving the combination of ring-opening polymerization of an amino acid N-carboxyanhydride (NCA) monomer using a primary amine initiator containing a nitroalkane group and a subsequent terminal conversion. The formed peptide was fully characterized by NMR, FT-IR, and MALDI-TOF MS measurements. The catalyst-free grafting reaction of the formed functionalized peptide with rubbers containing double bonds was achieved with high efficiency via an environmentally benign process. These results surely contributed to the development of novel peptide-grafted polymers.

Combustion mechanism and model free kinetics of different origin coal samples: Thermal analysis approach

Five coal samples from different origins are characterized for their pyrolysis and combustion features using coupled thermogravimetry - mass spectrometry (TG-MS). The samples are heated at temperatures ranging from 25 to 900 °C in air atmosphere under heating rates of 10, 20, and 30 °C/min. The characteristic temperatures (initial, peak, burn out), reaction intervals, mass loss rate, ash residues, ignition and combustion performances, an ignition-combustion index and the reactivities of the coal samples are calculated and the associated heating rate effects are estimated. The less reactive coal exhibits higher peak temperature in conversion and low value of ignition index and reactivity. The reactivity of the coal samples varied in between 2.31 and 7.84 x102 (1/min). The main volatile and combustion products (H2, CH4, H2O, CO, CO2, C6H6, COS, SO2) release for the corresponding TG and temperatures are estimated using online 3D measurements of MS based on their relative intensities and relevancy. Ozawa-Flynn-Wall (OFW) and Kissinger-Akahira-Sunose (KAS) type model free kinetic methods are applied to determine the activation energies of the coals which are exhibited in-between 44.6 - 75.1 kJ/mol and 50.5–96.6 kJ/mol using OFW and KAS methods respectively. The estimated kinetic constants are compared and found consistent with combustion performance parameters.

Synthesis and Spectral Identification of Three Schiff Bases with a 2-(Piperazin-1-yl)-N-(thiophen-2-yl methylene)ethanamine Moiety Acting as Novel Pancreatic Lipase Inhibitors: Thermal, DFT, Antioxidant, Antibacterial, and Molecular Docking Investigations.

Three new tetradentate NNNS Schiff bases (L1–L3) derived from 2-(piperidin-4-yl)ethanamine were prepared in high yields. UV–Visible and FTIR spectroscopy were used to monitor the dehydration reaction between 2-(piperidin-4-yl)ethanamine and the corresponding aldehydes. Structures of the derived Schiff bases were deduced by 1H and 13C NMR, FTIR, UV–Vis, MS, EA, EDS, and TG-derived physical measurements. DFT/B3LYP theoretical calculations for optimization, TD-DFT, frequency, Molecular Electrostatic Potential (MEP), and highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) / were performed for L2. The in vitro antimicrobial activities of the three Schiff bases were evaluated against several types of bacteria by disk diffusion test using Gentamicin as the standard antibiotic. Schiff bases revealed good antioxidant activity by the DPPH method, and the IC50 values were compared to the Trolox standard. Pancreatic porcine lipase inhibition assay of the synthesized compounds revealed promising activity as compared to the Orlistat reference.