Electron Impact Mass Spectrometry Research Articles

Ditechnetium Heptoxide Revisited: Solid-State, Gas-Phase, and Theoretical Studies.

Ditechnetium heptoxide was synthesized from the oxidation of TcO2 with O2 at 450 °C and characterized by single-crystal X-ray diffraction, electron-impact mass spectrometry (EI-MS), and theoretical methods. Refinement of the structure at 100 K indicates that Tc2O7 crystallizes as a molecular solid in the orthorhombic space group Pbca [a = 7.312(3) Å, b = 5.562(2) Å, c = 13.707(5) Å, and V = 557.5(3) Å3]. The Tc2O7 molecule can be described as corner-sharing TcO4 tetrahedron [Tc---Tc = 3.698(1) Å and Tc-OBri-Tc = 180.0°]. The EI-MS spectrum of Tc2O7 consists of both mononuclear and dinuclear species. The main dinuclear species in the gas-phase are Tc2O7 (100%) and Tc2O5 (56%), while the main mononuclear species are TcO3 (33.9%) and TcO2 (42.8%). The difference in the relative intensities of the M2O5 (M = Tc, Re) fragments (1.7% for Re) indicates that these group 7 elements exhibit different gas-phase chemistry. The solid-state structure of Tc2O7 was investigated by density functional theory methods. The optimized structure of the Tc2O7 molecule is in good agreement with the experimental one. Simulations indicate that the more favorable geometry for the Tc2O7 molecule in the gas-phase is bent (Tc-OBri-Tc = 156.5°), while a linear geometry (Tc-OBri-Tc = 180.0°) is favored in the solid-state.

Synthesis and antibacterial study of some s-substituted aliphatic analogues of 2-mercapto-5-(1-(4-toluenesulfonyl) piperidin-4-yl)-1,3,4-oxadiazole

Purpose: To synthesize a series of analogues of 1,3,4-oxadiazole and to evaluate their antibacterial activity.Methods: Ethyl piperidin-4-carboxylate (1) was mixed with 4-toluenesulfonyl chloride (2) in benignant conditions to yield ethyl 1-(4-toluenesulfonyl)piperidin-4-carboxylate (3) and then 1-(4- toluenesulfonyl)piperidin-4-carbohydrazide (4). Intermolecular cyclization of 4 into 2-mercapto-5-(1-(4- toluenesulfonyl) piperidin-4-yl)-1,3,4-oxadiazole (5) was obtained on reflux with CS2 in the presence of KOH. Molecule 5 was stirred with alkyl halides, 6a-i, in DMF in the presence of LiH to synthesize the final compounds, 7a-i. The structures of these molecules were elucidated by Fourier transform infra-red (FTIR) spectroscopy, proton nuclear magnetic resonance (1H-NMR) and electron impact mass spectrometry (EI-MS). Antibacterial activity was evaluated against five bacterial strains, namely, Salmonella typhi, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilis, with ciprofloxacin used as standard antibacterial agent.Results: Out of nine synthesized derivatives, compound 7a was the most active against three bacterial strains, S. typhi, E. coli and P. aeruginosa, with minimum inhibitory concentration (MIC) of 9.11 ± 0.40, 9.89 ± 0.45 and 9.14 ± 0.72 μM, respectively, compared with 7.45 ± 0.58, 7.16 ± 0.58 and 7.14 ± 0.18 μM, respectively, for the reference standard (ciprofloxacin). Similarly, compounds 7a - 7c showed relatively good antibacterial activity against B. subtilis strain while compound 7e - 7g revealed good results against S. typhi bacterial strain.Conclusion: The results indicate that S-substituted derivatives of the parent compound are more effective antibacterial agents than the parent compound, even with minor differences in substituents.Keywords: 1,3,4-Oxadiazole, Antibacterial activity, Ethyl piperidin-4-carboxylate, Sulfonamide

Metabolite profiles of formula milk compared to breast milk

Breast milk (BM) feeding is the gold standard in neonate nutrition. When BM is not available it can be substituted or integrated with commercial formula milk (FM) usually sold under different brands and formulations. In this work, the low-molecular-weight hydrophilic compounds in milk were studied by gas chromatography electronic impact mass spectrometry (GC–MS), comparing eight different FM brands with BM samples. With the aid of multivariate statistical data analysis, a marked variability among FM brands, especially driven by the presence of prebiotics in their formulation, was highlighted. Quali-quantitative differences were found between FM and BM. Orotic acid and isomaltulose were found exclusively in FM, while phenylalanine and tyrosine levels were high in two FM brands. Moreover, higher levels of malic acid, sugars (glucose, fructose and galactose), and mannitol were detected in FM. On the other hand, BM showed a higher amino acid content. In conclusion, GC–MS proved to be a very sensitive analytical technique for the study of FM, highlighting metabolite differences among FM brands, and between FM and BM, that may have a possible strong impact on neonatal nutrition.

Cytotoxic Compounds from the Saudi Red Sea Sponge Xestospongia testudinaria.

Bioassay-guided fractionation of the organic extract of the Red Sea sponge Xestospongia testudinaria led to the isolation of 13 compounds including two new sterol esters, xestosterol palmitate (2) and xestosterol ester of l6′-bromo-(7′E,11′E,l5′E)-hexadeca-7′,11′,l5′-triene-5′,13′-diynoic acid (4), together with eleven known compounds: xestosterol (1), xestosterol ester of 18′-bromooctadeca-7′E,9′E-diene-7′,15′-diynoic acid (3), and the brominated acetylenic fatty acid derivatives, (5E,11E,15E,19E)-20-bromoeicosa-5,11,15,19-tetraene-9,17-diynoic acid (5), 18,18-dibromo-(9E)-octadeca-9,17-diene-5,7-diynoic acid (6), 18-bromooctadeca-(9E,17E)-diene-7,15-diynoic acid (7), 18-bromooctadeca-(9E,13E,17E)-triene-7,15-diynoic acid (8), l6-bromo (7E,11E,l5E)hexadeca-7,11,l5-triene-5,13-diynoic acid (9), 2-methylmaleimide-5-oxime (10), maleimide-5-oxime (11), tetillapyrone (12), and nortetillapyrone (13). The chemical structures of the isolated compounds were accomplished using one- and two-dimensional NMR, infrared and high-resolution electron impact mass spectroscopy (1D, 2D NMR, IR and HREIMS), and by comparison with the data of the known compounds. The total alcoholic and n-hexane extracts showed remarkable cytotoxic activity against human cervical cancer (HeLa), human hepatocellular carcinoma (HepG-2), and human medulloblastoma (Daoy) cancer cell lines. Interestingly, the dibrominated C18-acetylenic fatty acid (6) exhibited the most potent growth inhibitory activity against these cancer cell lines followed by Compounds 7 and 9. Apparently, the dibromination of the terminal olefinic moiety has an enhanced effect on the cytotoxic activity.

Synthesis, Characterization, Antibacterial, α-Glucosidase Inhibition and Hemolytic Studies on Some New N-(2,3- Dimethylphenyl)benzenesulfonamide Derivatives

Purpose: To synthesize a series of new N-(2,3-dimethylphenyl)benzenesulfonamide derivatives with pharmacological analysis. Methods: N-(2,3-Dimethylphenyl)benzenesulfonamide (3) was synthesized by the reaction between 2,3-dimethylaniline (1) and benzenesulfonyl chloride (2) in aqueous basic medium. Compound 3 was further treated with various alkyl/aralakyl halides (4a-m) to yield new compounds, 5a-m, in a weak basic aprotic polar organic medium. The proposed structures of synthesized compounds were confirmed using proton-nuclear magnetic resonance (1H-NMR), infra red spectroscopy (IR) and electron impact mass spectrometry (EIMS). The synthesized compounds were screened for in vitro antibacterial, antienzymatic and hemolytic activities using standard procedures. Results: All the synthesized compounds showed moderate to high activity against Gram-positive and Gram-negative bacterial strains. The molecules 5g and 5j exhibited good inhibition of α-glucosidase enzyme with half-maximal inhibitory concentration (IC 50 ) of 59.53 ± 0.01 and 55.31 ± 0.01 μmoles/L, respectively, relative to acarbose with IC 50 of 38.25 ± 0.12 μmoles/L. All the compounds exhibited cytotoxicity levels ranging from 27.20 ± 0.24 to 5.20 ± 0.41 %, relative to Triton X-100. Conclusion: Compound 5f is the most potent antibacterial while 5j is the best α-glucosidase inhibitor; 5e showed the least cytotoxicity. Keywords: 2,3-Dimethylaniline, Antibacterial activity, Anti-enzymatic activity, α-Glucosidase inhibitor, Hemolytic activity, Sulfonamides

New α-Glucosidase inhibitors from <i>Croton bonplandianum Croton bonplandianum</i> Baill (Euphorbiaceae)

Purpose: To isolate and evaluate α-glucosidase inhibitors from dichloromethane extract of Croton bonplandianum Baill as probable remedy for management of diabetes. Methods: Activity-guided isolation of constituents from dichloromethane extract was carried out. Fractionation of dichloromethane extract by column chromatography on silica gel and Sephadex LH 20 using different mobile phase systems led to the isolation of compounds (A-I). The structures of these isolated compounds were established by ultraviolet (UV) and infrared (IR) spectroscopy. Proton nuclear magnetic resonance ( 1 H NMR), 13 C NMR and mass spectrophotometry, electron impact mass spectroscopy (EIMS) and high resolution mass spectroscopy (HRMS) were used for structural elucidation. All the isolated compounds were screened for their α-glucosidase inhibitory activity using standard in vitro α-glucosidase inhibition assay. Acarbose was used as positive control. Results: On the basis of their physical and spectral data from literature, the isolated compounds were identified as n-pentacosanyl-n-nonadeca-7′-en-9′-α-ol 1′-oate (A), n-tridecanyl n-octadec-9,12-dienoate (B), nonacosyl hexadecanoate (C), heptacosanoic acid (D), 1,3,5-trihydroxy-2-hexadecanoylamino- (6e,9e) heptacosdiene (E),cumarin (F), betulin (G), stigmasterol (H), and 3,5-dimethoxy 4-hydroxy cinnamic acid (I).Compounds F, GandI possessed significant α glucosidase inhibitory activity in a concentration-dependent manner with 50 % inhibitory concentration (IC 50 ) values ranging from 23.0 to 26.7 μg/mL, relative to that of the positive control, acarbose (IC 50 , 38.2 μg/mL). Conclusion: The plant contains bioactive compounds with α-glucosidase inhibitory activity. This lendssome support for the traditional use of this herb in the management of diabetes. Compound F, GandI possessed significant α glucosidase inhibitory activity in a concentration-dependent manner and may be developed as a new α-glucosidase inhibitor. Keywords: α-Glucosidase, Inhibition, Diabetes, Acarbose, Cumarin, Betulin, 3,5 Dimethoxy 4-hydroxy cinnamic acid, Croton bonplandianum

Organic compound composition in soil and sediments collected in Jackson, Mississippi

ABSTRACTThe aim of our study was to identify organic pollutants found in soil and sediment samples collected within the Jackson, MS metropolitan area. The chemical characterization of the organic compound fractions in soil and sediment samples was carried out by separating the organic fraction using column chromatography (CC) and quantitatively analyzing the polycyclic aromatic hydrocarbons (PAHs), n-alkanes and other organic compounds using gas chromatography–electron impact mass spectrometry (GC–MS). Fifty-six compounds were identified and quantified in the soil samples and 33 compounds were identified and quantified in the sediment samples. The PAHs, n-alkanes and other organic compound profiles in the soil and sediment samples were compared. The percentage contents of the organic compounds in the soil samples were very diverse (from traces to 12.44 ± 1.47%). The compounds present in the highest concentrations were n-alkanes: n-C31 (12.44 ± 1.47%), n-C29 (11.64 ± 1.21%), and n-C33 (8.95 ± 1.08%). The components occurring in smaller quantities (from 1% to 5%) were 2 PAHs (fluoranthene 1.28 ± 0.25%, pyrene 1.16 ± 0.20%), 10 n-alkanes from n-C21 (1.25 ± 0.29%) to n-C32 (2.67 ± 0.52%) and 11 other compounds (e.g., 2-pentanol, 4-methyl (3.33 ± 0.44%), benzyl butyl phthalate (4.25 ± 0.59%), benzenedicarboxylic acid (1.14 ± 0.08%), ethane, 1,1-diethoxy (3.15 ± 0.41) and hexadecanoic acid (2.52 ± 0.34). The soil samples also contained 30 compounds present in concentrations <1% (e.g., anthracene (0.13 ± 0.04%), n-C20 (0.84 ± 0.21%) and acetic acid (0.12 ± 0.04%). The compounds present in the highest concentrations in the sediment samples were PAHs: pyrene (7.73 ± 1.15%) and fluoranthene (6.23 ± 1.07%) and n-alkanes: n-C31 (6.74 ± 1.21%), n-C29 (6.65 ± 0.98%) and n-C27 (6.13 ± 1.09%). The remaining organic compounds were present in smaller quantities (< 5%).

GC-PCI-MS/MS and LC-ESI-MS/MS databases for the detection of 104 psychotropic compounds (synthetic cannabinoids, synthetic cathinones, phenethylamine derivatives).

Designer psychotropic compounds continue to be a major problem in Japan and all around the world. Electron impact mass spectrometry (GC-EI-MS) and liquid chromatography with electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) data on these compounds have been widely reported. In this report, we present a detection method that has been rarely utilized to analyze these types of compounds, gas chromatography with positive chemical ionization and tandem mass spectrometry (GC-PCI-MS/MS). We report on the development of GC-PCI-MS/MS and LC-ESI-MS/MS databases of 104 psychotropic compounds, including 32 cannabinoid derivatives, 29 cathinone derivatives, 34 phenethylamine derivatives, and several other designer compounds. Using this database, we were able to detect 5 psychotropic compounds in an actual forensic autopsy case. If GC-PCI-MS/MS is used together with the more established methods of GC-EI-MS and LC-ESI-MS/MS, we believe the forensic toxicology community could be better prepared to deal with the challenges of these ever-changing compounds.

A New Octadecenoic Acid Derivative from Caesalpinia gilliesii Flowers with Potent Hepatoprotective Activity.

Background:Caesalpinia gilliesii Hook is an ornamental shrub with showy yellow flowers. It was used in folk medicine due to its contents of different classes of secondary metabolites. In our previous study, dichloromethane extract of C. gilliesii flowers showed a good antioxidant activity.Aim of the Study:Isolation and identification of bioactive hepatoprotective compounds from C. gilliesii flowers dichloromethane fraction.Materials and Methods:The hepatoprotective activity of dichloromethane fraction and isolated compounds were studied in CCl4-intoxicated rat liver slices by measuring liver injury markers (alanine aminotransferase, aspartate aminotransferase and glutathione [GSH]). All compounds were structurally elucidated on the basis of electron ionization-mass spectrometry, one- and two-dimensional nuclear magnetic resonance.Results:A new 12,13,16-trihydroxy-14(Z)-octadecenoic acid was identified in addition to the known β-sitosterol-3-O-butyl, daucosterol, isorhamnetin, isorhamnetin-3-O-rhamnoside, luteolin-7,4’-dimethyl ether, genistein-5-methyl ether, luteolin-7-O-rhamnoside, isovanillic acid, and p-methoxybenzoic acid. Dichloromethane fraction and isorhamnetin were able to significantly protect the liver against intoxication. Moreover, the dichloromethane fraction and the isolated phytosterols induced GSH above the normal level.Conclusion:The hepatoprotective activity of C. gilliesii may be attributed to its high content of phytosterols and phenolic compounds.SUMMARY Bioactive Hepatoprotective phytosterols and phenolics from chloroform extract of Caesalpinia gilliesii Abbreviations used: ALT: Alanine Aminotransferase; AST: Aspartate aminotransferase; GSH: Glutathione; SC50: Scavenging Capacity 50 (SC 50); COSY: Correlation spectroscopy; NMR: Nuclear Magnetic Resonance; CC: Column chromatography; EI-MS: Electron-impact mass spectrometry; HSQC: Heteronuclear single-quantum correlation.

Syntheses, Characterization and DFT Analysis of Two Novel Thiaheterohelicene Derivatives

Two novel thiaheterohelicene derivatives were synthesized from the corresponding 2,2'-(2,6-naphthalenediyl-di-2,1-ethenediyl) bis-thiophene and its dimethyl substituted analogue 2,2'-(2,6-naphthalenediyldi-2,1-ethenediyl) bis-2’’-methylthiophene using oxidative photo cyclization reaction. The compounds were characterized by 1H NMR, electron impact-mass spectrometry, elemental analyses, and the absolute molecular structures were determined by single crystal X-ray diffraction analysis. They crystallized under monoclinic system with space group P21/n for the unsubstituted compound and P21/c for the methyl substituted compound, respectively. The dihedral angle between the terminal thiophene ring and the molecular center was observed to be 20.82? for the unsubstituted compound and 14.27? for the methyl substituted compound, respectively. Furthermore, molecules oriented as herringbone structures by intermolecular π-π stacking in the crystals. The relative study of the actual arrangement of these molecules has been carried out using X-ray diffraction analysis. The two molecules have different crystal packing. The molecule 3b has herring bone like arrangement due to the substituent bulkiness and weak CH-π interaction. On the other hand, the molecular packing of molecule 3a is not herringbone probably due to the multiple weak intermolecular CH-S short contacts between columns consisting of stacked molecules.

Study of Mass Spectra of Some Indole Derivatives

In the work, a study of mass fragmentation routes by the electron-impact mass spectrometry data has been examined for two open chain intermediates of indole derivatives and two pyrroloquinolines. By the isolation of open chain intermediate and the mass spectra, the structures of pyrroloquinoline have been confirmed.

Масс-спектрометрия электронного удара в анализе включения стабильных изотопов дейтерия и углерода-13 в молекулы аминокислот биологических объектов

Масс-спектрометрия электронного удара в анализе включения стабильных изотопов дейтерия и углерода-13 в молекулы аминокислот биологических объектов

Determination of Neutral Monosaccharides as Per-O-methylated Derivatives Directly from a Drop of Whole Blood by Gas Chromatography-Mass Spectrometry.

A new analytical procedure was developed for the simultaneous quantification of neutral monosaccharides from a drop of whole blood using gas chromatography-mass spectrometry analysis (GC-MS) of their per-O-methylated derivatives. The per-O-methylation reaction with methyl iodide and solid sodium hydroxide in methyl sulfoxide was used for the first time for analysis of blood monosaccharides. A blood drop volume of 0.6 μL was used without special purification. The elimination of the undesirable components was carried out during methylation in the presence of a strong base and by liquid extraction of the per-O-methylated monosaccharides. The neutral monosaccharides with an anomeric center gave four per-O-methylated isomers, which were well-separated using a capillary column. Identification was done by electron impact mass spectrometry fragmentation, retention times, and library searching. The limits of detection were determined for standards and varied from 2.0 to 2.3 ng mL(-1). Recoveries for human blood samples varied from 99.22% to 99.65%. The RSD values ranged from 1.92 to 2.37. The method is fast, sensitive, reproducible, and an alternative to current methods for quantitative analysis of blood monosaccharides.

Chemical composition and antibacterial activity of essential oil of Launaea lanifera Pau grown in Algerian arid steppes

ObjectiveTo evaluate the essential oil composition and the antibacterial activity of an Algerian endemic plant, Launaea lanifera Pau (L. lanifera), grown in arid steppe regions. MethodsL. lanifera essential oil was isolated from aerial parts by steam distillation and its chemical composition was evaluated by gas chromatography-flame ionization detector and gas chromatography with electron impact mass spectrometry. Furthermore, its in vitro antibacterial activity against four bacterial strains was tested following the agar disk diffusion method. ResultsThis species had a very low essential oil yield (0.005%). Twenty-four (92.6%) individual components were identified. The main constituents were hexahydrofarnesyl acetone (31.6%), (E)-β-ionone (8.5%), (E)-β-damascenone (7.0%), 2-methyltetradecane (3.8%), n-heptadecane (3.8%), limonene (2.8%) and β-caryophyllene (2.8%). No noteworthy antimicrobial activity was observed on the tested bacteria, neither Gram negative nor Gram positive. ConclusionsThis is the first report on the volatile constituents and antibacterial activity of L. lanifera. The studied essential oil does not possess significant activity against the tested microorganisms.

Synthesis of N'-Substituted-2-(5-(4-Chlorophenyl)-1,3,4- oxadiazol-2-ylthio)acetohydrazide Derivatives as Suitable Antibacterial Agents

Purpose: To evaluate antibacterial activity of a series of molecules bearing 1,3,4-oxadiazole and azomethine moieties.Methods: The 4-chlorobenzoic acid (1) was precursor to N'-substituted-2-(5-(4-chlorophenyl)-1,3,4- oxadiazol-2-ylthio)acetohydrazide, 8a-p, through a multistep synthesis of corresponding ester, 2, hydrazide, 3 and 1,3,4-oxadiazole, 4. The molecule, 4, was subjected to electrophilic substitution by ethyl-2-bromoacetate to yield 5 which was stepped to 2-(5-(4-chlorophenyl)-1,3,4-oxadiazol-2- ylthio)acetohydrazide (6). The target molecules, 8a-p, were synthesized by nucleophilic addition of 6 to arylaldehydes, 7a-p. The proposed structures of all the synthesized molecules were elucidated by Infra Red (IR), Proton Nuclear Magnetic Resonance (1H-NMR) and Electron Impact Mass Spectrometry (EIMS) spectral data. Antibacterial activity was evaluated by the principle that microbial growth is in a log phase of growth and so results in increased absorbance of broth medium which is observed.Results: The molecule, 8b, was active against S. aureus and 8c against S. typhi only. The molecule, 8p, was the most active against S. typhi with minimum inhibitory concentration (MIC) value of 10.04 ± 1.25 μM while 8e was active against E. coli with MIC of 9.45 ± 1.00 μM, both relative to the reference standard, ciprofloxacin, which displayed MIC of 9.13 ± 2.00 and 8.90 ± 1.65 μM, respectively.Conclusion: Most of the synthesized molecules exhibit 50 % antibacterial activity relative to the reference. Molecules 8b and 8c are the least active compounds.Keywords: 1,3,4-Oxadiazole, 4-Chlorobenzoic acid, Antibacterial activity, Azomethine

Quantification of Polyfunctional Thiols in Wine by HS-SPME-GC-MS Following Extractive Alkylation.

Analyses of key odorous polyfunctional volatile thiols in wines (3-mercaptohexanol (3-MH), 3-mercaptohexylacetate (3-MHA), and 4-mercapto-4-methyl-2-pentanone (4-MMP)) are challenging due to their high reactivity and ultra-trace concentrations, especially when using conventional gas-chromatography electron impact mass spectrometry (GC-EI-MS). We describe a method in which thiols are converted to pentafluorobenzyl (PFB) derivatives by extractive alkylation and the organic layer is evaporated prior to headspace solid phase microextraction (HS-SPME) and GC-EI-MS analysis. Optimal parameters were determined by response surface area modeling. The addition of NaCl solution to the dried SPME vials prior to extraction resulted in up to less than fivefold improvement in detection limits. Using 40 mL wine samples, limits of detection for 4-MMP, 3-MH, and 3-MHA were 0.9 ng/L, 1 ng/L, and 17 ng/L, respectively. Good recovery (90%–109%) and precision (5%–11% RSD) were achieved in wine matrices. The new method was used to survey polyfunctional thiol concentrations in 61 commercial California and New York State wines produced from V. vinifera (Riesling, Gewürztraminer, Cabernet Sauvignon, Sauvignon blanc and non-varietal rosé wines), V. labruscana (Niagara), and Vitis spp. (Cayuga White). Mean 4-MMP concentrations in New York Niagara (17 ng/L) were not significantly different from concentrations in Sauvignon blanc, but were significantly higher than 4-MMP in other varietal wines.

Direct condensation of lactic acid in the presence or absence of supported zirconium sulfate

ABSTRACTDirect condensation of l‐lactic acid was studied, aiming at highly crystalline and enantiopure high molecular weight (MW) products. Catalyst‐free polylactic acid (PLA) with weight average MW of 80,000 g mol−1, based on PLA standards, and a crystallinity of 75% is synthesized at 140°C in a fixed‐bed reactor under vacuum or nitrogen purging. Supported zirconium sulfate is found to be an efficient and enantioselective catalyst for the melt and solid‐state post‐condensation of short‐chain prepolymers. Small‐molecule monohydroxy alcohols, aldehydes, di‐ and monocarboxylic acids (e.g., acrylic acid [1,700 ppm], propionic acid [1,800 ppm]) are detected in the lactic acid and prepolymers by high performance liquid chromatography, electron spray ionization, and electron impact mass spectroscopy. Thermal degradation of polymer chains, the crystallinity of the prepolymer, and the presence of monofunctional impurities are crucial parameters for the limitation of the MW of the resulting product. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42444.

Allium sativum produces terpenes with fungistatic properties in response to infection with Sclerotium cepivorum

This study investigated terpene biosynthesis in different tissues (root, protobulb, leaf sheath and blade) of in vitro-grown garlic plants either infected or not (control) with Sclerotium cepivorum, the causative agent of Allium White Rot disease. The terpenes identified by gas chromatography–electron impact mass spectrometry (GC-EIMS) in infected plants were nerolidol, phytol, squalene, α-pinene, terpinolene, limonene, 1,8-cineole and γ-terpinene, whose levels significantly increased when exposed to the fungus. Consistent with this, an increase in terpene synthase (TPS) activity was measured in infected plants. Among the terpenes identified, nerolidol, α-pinene and terpinolene were the most abundant with antifungal activity against S. cepivorum being assessed in vitro by mycelium growth inhibition. Nerolidol and terpinolene significantly reduced sclerotia production, while α-pinene stimulated it in a concentration-dependent manner. Parallel to fungal growth inhibition, electron microscopy observations established morphological alterations in the hyphae exposed to terpinolene and nerolidol. Differences in hyphal EtBr uptake suggested that one of the antifungal mechanisms of nerolidol and terpinolene might be disruption of fungal membrane integrity.

In-situ analysis of volatile products from lignite pyrolysis with pyrolysis-vacuum ultraviolet photoionization and electron impact mass spectrometry

Pyrolytic species of two kinds of lignites (samples A and B) are investigated in-situ with pyrolysis-vacuum ultraviolet photoionization/electron impact mass spectrometry (PVUVPI/EIMS). Mass spectra of pyrolytic fragments are measured during temperature-programmed pyrolysis process of two lignite samples and the intensity profiles of the pyrolytic species are estimated in different temperatures. Experimental results show that H2, H2O, CO, and CO2 are dominant inorganic gaseous products and their characteristic temperatures are in accord with the temperatures of related chemical bonds cleavage. Mononuclear aromatics are dominant organic pyrolysis products, and many olefin species are also identified. The differences between samples A and B on macromolecular structures make the distribution of pyrolytic products different. In addition, the peak of H2S and CH3SH are both clearly observed in mass spectra of sample B, which could come from thioether bonds decomposition. This work also illustrates that the PVUVPI/EIMS performs very well in in-situ analysis pyrolytic products.

Electronic structure and noncovalent interactions within ion-radical complexes of N-(2-furylmethyl)aniline molecular ions.

We investigate the electronic structure and noncovalent interactions within cation-radical complexes that are relevant in the electron impact mass spectrometry of N-(2-furylmethyl)anilines, 4-R-C6H4-NH-CH2-C4H3O with (R = -H, -OCH3, -CH3, -F, -Cl, -Br). In particular, we consider the reactive intermediates that precede the final products of two previously suggested dissociation pathways for these systems, i.e., (i) a direct cleavage of the NH-CH2 bond and (ii) an isomerization/fragmentation mechanism. The study is performed by means of correlated calculations (UCCSD and UMP2) together with density functionals (UM06 an UM06-2x) along with the triple-ζ quality basis set 6-311++G(2d,2p). In addition, we carried out a topological analysis of the electron density in accordance with the quantum theory of atoms in molecules (QTAIM) together with the examination of the noncovalent interaction (NCI) index. In contrast with previous studies based on the UB3LYP approximation, we could determine the transition states associated with both fragmentation pathways. The Rice-Ramsperger-Kassel-Marcus theory, used to determine the relative importance of these dissociation mechanisms, indicates that whereas the direct cleavage and the isomerization/fragmentation reaction routes have similar constant rates at low energy, the former prevails when the energy of the system is increased. The QTAIM analysis reveals that the charge of the cation-radical complex is mainly located on either a furfuryl (direct cleavage mechanism) or a pyrylium (isomerization/fragmentation pathway) ion and that these units interact with a neutral radical aniline moiety. The localization of the positive charge in either a furfuryl or pyrylium cation is in agreement with the preminecence of the m/z = 81 fragment in the mass spectrometry of N-(2-furylmethyl)anilines. Moreover, the QTAIM properties indicate that the α unpaired electron of the system is principally distributed over the nitrogen and the ortho and para carbon atoms with respect to the -NH group in the R-C6H4-NH unit. The investigation of the NCI index and the intermolecular bond critical points and bond paths gives an account of the NCIs linking the radical cation clusters under consideration. Finally, we found correlations which indicate that the concentration of the m/z = 81 fragment in a mass spectrum is reduced with the interaction energy of the radical complex from which it is originated. Altogether, this work shows how the combination of suitable electronic structure calculations along with post wave function analyses can yield important insights about the formation and properties of cation-radical complexes relevant in mass spectrometry.