High-resolution Electron Impact Research Articles

Synthesis, Spectral Analysis and Molecular Docking Investigation of Thiadiazole Based Sulfonamide Derivatives: An Effective Approach Toward Alzheimer's Disease

AbstractAlzheimer's disease (AD), a neurodegenerative condition is expected to affect 152 million in 2050. The current study comprises the evaluation of thiazole based thiadiazole bearing sulfonamide derivatives to treat Alzheimer's disease. A series of compounds (1‐15) were synthesized and were studied for their anti‐Alzheimer's potential. Their IC50 values lie in the range between (19.20±0.20 nM–2.50±0.20 nM) for AChE and (19.80±0.20 nM–3.30±0.50 nM) for AChE. Among all of them, analog 2, 7, 9, and 15 were reported to possess significant activity. Among all the members of series, compound 15 having IC50=2.50±0.20 nM and 3.30±0.50 nM for AChE and BuChE, respectively, emerged as the most promising candidate due to the presence of two electronegative fluorine (F) atoms. The small and highly electronegative fluorine atoms have the ability to block the enzyme's activity by forming strong hydrogen bonds with the amino acids of the target enzymes, thereby inhibiting their function. The efficacy of these novel compounds was studied in comparison to the standard drug donepezil having IC50=5.80±0.30 nM for AChE and IC50=6.30±0.81 nM BuChE. For further assessment of inhibition potential and mode of inhibition, molecular docking study of all the potent compounds was carried out. Further, the structural identity of the synthesized compounds was confirmed using various spectroscopic techniques, including 1H‐NMR, 13C‐NMR, and High‐Resolution Electron Impact (HREI) Mass spectrometry, which provided detailed information about their molecular structure. ADME analysis of all the synthesized compounds confirmed their potential as drugs, indicating favorable pharmacokinetic properties and a promising drug profile.

Second phase structure analysis and wear behavior of the ultra-high manganese steel

The high manganese steel is widely used in wear-resisting parts of the cone crusher, such as the grinding mill wall and crushing wall. In this work, the microstructure and wear resistance of an ultra-high manganese steel (Mn18Cr2Mo) were analyzed by electron diffraction and high-resolution transmission electron microscope (HRTEM) observation and impact abrasive wear test. The results show that there are spherical or block Mo2C and strip-like (Fe, Cr)3C phases in Mn18Cr2Mo manganese steel. The orientation of the Mo2C phase and the austenite matrix are [001]austenite// Mo2C, (020)austenite//(020)Mo2C, austenite//(202)Mo2C and austenite//(242)Mo2C. The that of the (Fe, Cr)3C phase and the austenite matrix are [011]austenite// (Fe, Cr)3C and austenite//(210)(Fe, Cr)3C. Besides, austenite is approximately parallel to (Fe, Cr)3C. The interface relation of (002)austenite is approximately parallel to (Fe, Cr)3C. Owing to high density dislocations, deformation bands, microcrystal and non-crystalline, the wear resistance of the Mn18Cr2Mo manganese steel is 1.83 times that of the Mn13 manganese steel under the impact abrasive wear test.

Momentum transfer dependence behavior of the 3 s-1nl autoionization states of argon studied by high-resolution fast electron impact

SynopsisMomentum transfer dependence behavior of the autoionization states plays an unique role in understanding the electronic correlation effect. In the present work, the 3s-1nl autoionization states and their peak profiles of argon have been measured at different scattering angles by fast electron impact. The momentum transfer dependence behaviors of the dipole-allowed and dipole-forbidden autoionization states of argon have been elaborated.

Ammonium Salts as a Source of Small Molecules Observed with High-Resolution Electron-Impact Ionization Mass Spectrometry.

Recent high-resolution in situ mass spectrometry at comet 67P/Churyumov-Gerasimenko visited by European Space Agency's Rosetta spacecraft raised the question, if sublimating ammonium salts can unequivocally be detected in the cometary coma. In laboratory experiments with the twin model of the space instrument, two prototypic ammonium salts NH4B, namely, ammonium chloride (B = Cl-) and ammonium formate (B = HCOO-) (as well as methodologically relevant isotopologues), were allowed to sublimate in vacuum while mass spectra were collected. High-resolution electron-impact ionization mass spectrometry provides an outstanding experimental tool to investigate the complex physicochemical processes occurring during the sublimation of ammonium salts. Sublimation of ammonium chloride led to the observation of the ammonium cation NH4+ and the chloramide molecule NH2Cl in the neutral gas mode of the instrument. These observations could be jointly interpreted as indirect evidence for the existence of a neutral gaseous parent species (either as the molecular complex NH3···HB or the double-ionic species NH4+···B-). However, the qualitative fragmentation pattern we present for 13C15N-ammonium formate suggests an alternative route of NH4+ production within the ionization region of the instrument, namely, by protonation/hydrogenation. Besides NH4+, other species were observed that were formed in protonation/hydrogenation reactions. Moreover, together with the two major species from the decomposition of the salt, ammonia and formic acid, three minor species also contributed to the fragmentation pattern: HCN/HNC, HOCN/HNCO, and CH3NO. Like chloramide, formamide (CH3NO) also is a secondary species probably formed in a pseudo-intramolecular chemical reaction while ammonia and the respective acid are in a state of association. HCN/HNC and HOCN/HNCO are ternary products coming out of formamide decomposition reactions. We discuss our experimental findings, summarized in a tentative chemical reaction network, in light of the available theoretical literature and highlight their relevance for the interpretation of in situ measurements in space research.

Synthesis of 4-substituted ethers of benzophenone and their antileishmanial activities.

Leishmaniasis is a vector-borne protozoan disease; it mainly originates from the bite of sandfly and initiated when parasite is transmitted to human at metacyclic flagellated promastigote form. In the current study, a synthesis of a series of 4-substituted benzophenone ethers 1–20 was carried out in good yields and their in vitro antileishmanial activities were also screened. Among synthetic derivatives, 15 compounds 1, 3, 5–12, 15 and 17–20 showed antileishmanial activities against promastigotes of Leishmania major with IC50 values in the range of 1.19–82.30 µg ml−1, and the values were compared with those of the standard pentamidine (IC50 = 5.09 ± 0.09 µg ml−1). Our study identified a series of new antileishmanial molecules as potential leads. Structures of these synthetic compounds were deduced by different spectroscopic techniques, such as 1H and 13C nuclear magnetic resonance, electron impact and high-resolution electron impact mass spectrometry and IR.

Antioxidant xanthones and anthraquinones isolated from a marine-derived fungus Aspergillus versicolor

Chemical examination of an EtOAc extract of cultured Aspergillus versicolor fungus from deep-sea sediments resulted in the isolation of four xanthones, eight anthraquinones and five alkaloids, including a new xanthone, oxisterigmatocystin D (1) and a new alkaloid, aspergillusine A (13). High resolution electron impact mass spectrometry (HR-EI-MS), FT-IR spectroscopy, and NMR techniques were used to elucidate the structures of these compounds, and the absolute configuration of compound 1 was established by its NMR features and coupling constant. Furthermore, the biosynthesis pathway of these xanthones and anthraquinones were deduced, and their antioxidant activity and cytotoxicity in human cancer cell lines (HTC-8, Bel-7420, BGC-823, A549, and A2780) were evaluated. The trolox equivalent antioxidant capacity (TEAC) assay indicated most of the xanthones and anthraquinones possessing moderate antioxidant activities. The Nrf2-dependent luciferase reporter gene assay revealed that compounds 6, 7, 9, and 12 potentially activated the expression of Nrf2-regulated gene. In addition, compounds 5 and 11 showed weak cytotoxicity on A549 with the IC50 values of 25.97 and 25.60 μmol·L−1, respectively.

Microstructure Characterization of Fiber Laser Welds of S690QL High-Strength Steels

The use of fiber laser welding to join S690QL steels has attracted interest in the field of construction and assembly. Herein, 13-mm-thick S690QL welded joints were obtained without filler materials using the fiber laser. The as-welded microstructures and the impact energies of the joints were characterized and measured using electron microscopy in conjunction with high-resolution transmission electron images, X-ray diffraction, and impact tests. The results indicated that a single-sided welding technique could be used to join S690QL steels up to a thickness of 12 mm (fail to fuse the joint in the root) when the laser power is equal to 12 kW (scan speed 1 m/min). Double-side welding technique allows better weld penetration and better control of heat distribution. Observation of the samples showed that the fusion zone exhibited bainitic and martensitic microstructures with increased amounts of martensites (Ms) compared with the base materials. Also, the grains in the fusion zone increased in coarseness as the heat input was increased. The fusion zone exhibited increased hardness (397 HV0.2) while exhibiting a simultaneous decrease in the impact toughness. The maximum impact energy value of 26 J was obtained from the single-side-welded sample, which is greater than those obtained from the double-side-welded samples (maximum of 18 J). Many more dislocations and plastic deformations were found in the fusion zone than the heat-affected zone in the joint, which hardened the joints and lowered the impact toughness. The microstructures characterized by FTEM–energy-dispersive X-ray spectrometer also exhibited laths of M, as well as stacking faults and dislocations featuring high-density, interfacial structure ledges that occur between the high-angle grain boundaries and the M and bainite.

New oxaphenalene derivative from marine-derived Streptomyces griseorubens sp. ASMR4

Abstract During our search for novel bioactive compounds from extremophilic actinomycetes, the new Streptomyces griseorubens sp. ASMR4 was isolated from a soft coral collected in the Red Sea at the Hurghada coast, Egypt, and characterized taxonomically. It was fermented on large scale using a modified solid rice medium as the first example for actinomycetes so far. Work-up and purification of the strain extract using different chromatographic techniques afforded the new oxaphenalene derivative, 8-hydroxy-2-(2-hydroxypropyl)-7-acetyl-1-oxaphenalene (1a), together with seven known metabolites: ferulic acid (2), glycerol linoleate, linoleic acid methyl ester, (3R,4R)-3,4-dihydroxy-3-methylpentan-2-one/(3S,4R)-3,4-dihydroxy-3-methylpentan-2-one, anthranilic acid, phenylacetic acid, and benzoic acid. The chemical structure of the new compound (1a) was confirmed by extensive 1D and 2D NMR spectroscopy, high-resolution electron impact mass measurements, and by comparison with literature data. The antimicrobial activity of the strain extract and compounds 1a and 2 were studied using a panel of pathogenic microorganisms. The in vitro cytotoxicity of the bacterial extract was studied against the human cervix carcinoma cell line (KB-3-1) and its multi-drug-resistant subclone (KB-V1).

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.

New apoptosis-inducing sesquiterpenoids from the mycelial culture of Chinese edible fungus Pleurotus cystidiosus.

Two new bisabolane-type sesquiterpenoids, pleuroton A (1) and pleuroton B (2), and three clitocybulol derivatives, clitocybulol D (3), clitocybulol E (4), and clitocybulol F (5), were obtained from the mycelial culture of edible fungus Pleurotus cystidiosus O. K. Mill by repeated column chromatography over RP-18, Sephadex LH-20, and silica gel. Their structures were determined according to nuclear magnetic resonance data, high-resolution electron impact mass spectrometry, and circular dichroism spectra. These new sesquiterpenoids exhibited significant cytotoxicity against two human prostate cancer DU-145 and C42B cells in the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The median inhibitory concentration (IC50) of compounds 1, 2, 3, 4, and 5 was 174, 28, 233, 162, and 179 nM, respectively, against the DU-145 cell and was 104, 52, 163, 120, and 119 nM, respectively, against the C42B cell. Especially, pleuroton B (2) exhibited the strongest cytotoxity among these sesquiterpenoids, which was confirmed by the colony formation assay. Furthermore, pleuroton B (2) could trigger the apoptosis of DU-145 cells through the detection of apoptosis cells using annexin V-FITC staining by flow cytometry, the observation of condensed nuclei in the apoptosis cells, and the western blot analysis for the expression of apoptosis-related proteins Bcl-2, Bak, and Bax. Analysis of structure-activity relationships of these sesquiterpenoids revealed that the unusual functional moiety of pleuroton B should contribute to its significant bioactivity. These results display the pharmacological potential of P. cystidiosus.

The uptake of ClNO3 on film coatings of natural sea salt

Using a coated-insert flow tube reactor coupled to a high-resolution low-energy electron impact mass spectrometer, the uptake of chlorine nitrate on a salt film coating of natural sea salt (NSS) was studied under variation in the reactant concentration ([ClNO3] = (1–15) · 1012 cm−3), humidity ([H2O] = (0.01–2.2) · 1015 cm−3), and reactor temperatures of 295 and 423 K. The time-dependent character of the uptake coefficient γ(t) = γ ini exp(−t/τ) + γ ss [1 − exp(−t/τ)] with parameters of the initial (γ ini ) and steady-state (γ ss ) uptake and characteristic time dependent on [ClNO3] was established. The only detected gas phase uptake product was Cl2. The absence of the dependence of the steady-state uptake coefficent γ ss on humidity in the aforementioned [H2O] range was established. Based on the model description of experimental dependences in terms of the modified Langmuir adsorption model, the adsorption heat of chlorine nitrate on NSS and the constant of unimolecular decay rate of the ClNO3…Z surface complex with the formation of the Cl2 product were estimated. It follows from the comparison of these parameters for the initial and steady-state uptake that their adsorption heats are similar within the experimental error and the difference between the coefficients γ ini and γ ss is caused by the difference in activation energies of unimolecular decay. The coefficients γ ini , γ ss , and τ were estimated under tropospheric chlorine nitrate concentrations that are unavailable in laboratory conditions.

Feeding deterrents from the tubers of Boschniakia himalaica against the red flour beetle, Tribolium castaneum

In our screening program for new agrochemicals from Chinese medicinal herbs and local wild plants, MeOH/CHCl3 extract of the tubers of Boschniakia himalaica was found to possess strong feeding deterrent activity against the red flour beetle, Tribolium castaneum. From the MeOH/CHCl3 extract, three feeding deterrents were isolated by bioassay-guided fractionation. The constituent compounds were isolated and identified as 3β-acetoxyurs-12-en-28-oic acid (1), 3β-acetoxyurs-28,13-olide (2) and (+)-pinoresinol monoglucoside (3) based on high-resolution electron impact mass spectrometry and nuclear magnetic resonance. Compounds 1, 2 and 3 exhibited feeding deterrent activity against T. castaneumadults with ED50 values of 378, 940 and 609 ppm, respectively. Key words: Boschniakia himalaica, Tribolium castaneum, feeding deterrent.

Mosquito larvicidal activity of alkaloids and limonoids derived from Evodia rutaecarpa unripe fruits against Aedes albopictus (Diptera: Culicidae)

In recent years, uses of environment friendly and biodegradable natural insecticides of plant origin have received renewed attention as agents for vector control. During a screening program for new agrochemicals from Chinese medicinal herbs and local wild plants, the ethanol extract of Evodia rutaecarpa Hook f. et Thomas (Rutaceae) unripe fruits was found to possess larvicidal activity against the mosquitoes. The aim of this research was to determine larvicidal activity of the ethanol extract of E. rutaecarpa unripe fruits and the isolated constituents against the larvae of the Culicidae mosquito Aedes albopictus. The powder, 5 kg of the fruit material, was extracted with 30 l of 95 % ethanol, filtered, and evaporated to dryness in a rotary vacuum evaporator. The crude extract was then partitioned between methanol-water and n-hexane. The n-hexane fraction was evaporated off to given n-hexane extract. The aqueous layer was repartitioned with chloroform to provide chloroform extract after evaporation of the solvent. Further partitioning with ethyl acetate gave a residue after evaporation of the solvent. Bioactivity-directed chromatographic separation of chloroform extract on repeated silica gel columns led to the isolation of three alkaloids (evodiamine, rutaecarpine, and wuchuyuamide I) and two limonoids (evodol and limonin). The structures of the constituent compounds were elucidated based on high-resolution electron impact mass spectrometry and nuclear magnetic resonance. Evodiamine, rutaecarpine, and wuchuyuamide I exhibited strong larvicidal activity against the early fourth instar larvae of A. albopictus with LC(50) values of 12.51, 17.02, and 26.16 μg/ml, respectively. Limonin and evodol also possessed larvicidal activity against the Asian tiger mosquitoes with LC(50) values of 32.43 and 52.22 μg/ml, respectively, while the ethanol extract had a LC(50) value of 43.21 μg/ml. The results indicated that the ethanol extract of E. rutaecarpa and the five isolated constituents have a good potential as a source for natural larvicides.

New Antifungal Compounds from Aspergillus terreus Isolated from Desert Soil

Two new butyrolactone I derivatives: 3-[3-hydroxy-4-(3-methyl-but-2-enyl)-phenyl]-5-(-4-hydroxybenzyl)-4-methyl-dihydrofuran-2(3H)-one (1) and (Z)-3-[3-hydroxy-4-(3-methyl-but-2-enyl)-phenyl]-5-(-4-hydroxybenzylidene)-4-methyl-dihydrofuran-2(3H)-one (2), in addition to the previously described (S)-methyl-4-hydroxy-2-[4-hydroxy-3-(3-methyl-but-2-enyl)-benzyl]-3-(4-hydroxy-phenyl)-5-oxo-2,5-dihydro-furan-2-carboxylic acid methyl ester (3), were identified from a strain of Aspergillus terreus Thom (Trichocomaceae) isolated from desert soil. The antifungal activities of both intra- and extracellular metabolites of A. terreus grown on yeast extract sucrose and malt extract media were determined. Only the secondary metabolites of A. terreus grown on yeast extract sucrose medium were active against Aspergillus fumigatus RCMB 002008. The antifungal activity of A. terreus was attributed to the presence of the compounds (1) and (2), whose minimum inhibitory concentrations (MIC) against A. fumigatus were found to be 32.00 and 16.00 µg/mL respectively. Structure elucidation was carried out using UV spectrometry, electrospray ionization mass spectrometry (ESIMS), high resolution electron impact (HREIMS) spectrometry, (1)H- and (13) C-NMR, proton-proton correlation spectroscopy ((1)H-(1)H Cosy), distortionless enhancement by polarization transfer (DEPT), heteronuclear single quantum coherence (HSQC) and heteronuclear multiple bond correlations (HMBC) spectroscopy.

Evaluation of Homoleptic Guanidinate and Amidinate Complexes of Gadolinium and Dysprosium for MOCVD of Rare-Earth Nitride Thin Films

Metal−organic chemical vapor deposition (MOCVD) of thin films of two representative rare-earth nitrides is reported here for the first time. Four homoleptic, all-nitrogen-coordinated, rare-earth (RE) complexes were evaluated as precursors for the respective nitride thin film materials. Two guanidinato complexes [RE{(iPrN)2C(NMe2)}3] [RE = Gd (1), Dy (2)] and two amidinato complexes [RE{(iPrN)2CMe}3] [RE = Gd (3), Dy (4)] were compared and used either as single source precursors or together with ammonia for MOCVD of gadolinium nitride (GdN) and dysprosium nitride (DyN), respectively. The thermal properties of the precursors were studied and the fragmentation patterns were characterized by high-resolution electron impact−mass spectrometry (HR EI-MS). The obtained nitride films were investigated using a series of techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), nuclear reaction analysis (NRA), Rutherford backscattering (RBS), and X-ray photoelectron spectroscopy (XPS). The f...

All-Nitrogen Coordinated Amidinato/Imido Complexes of Molybdenum and Tungsten: Syntheses and Characterization

The first all-nitrogen coordinated bis(alkylamidinato)/bis(alkylimido) complexes of molybdenum and tungsten, [Mo(NtBu)(2){(iPrN)(2)CMe}(2)]and [W(NtBu)(2){(iPrN)(2)CMe}(2)], have been synthesized and fully characterized by (1)H and (13)C NMR spectroscopy, elemental analyses, high-resolution electron impact mass spectrometry, and Fourier transform infrared spectroscopy. Density functional theory calculations of the tungsten complex allow for geometry optimization and structural characterization by assignment of the NMR data, in particular a comparison of the experimental (13)C NMR signals with the calculated ones. Both compounds sublime without decomposition at 130 °C and 1 mTorr and show rapid decomposition above 250 °C, hence representing promising vapor-phase deposition routes for metal nitride based thin-film materials.

Lignans from the Tuber-barks of Colocasia antiquorum var. esculenta and Their Antimelanogenic Activity

Colocasia antiquorum var. esculenta , a variant of C. antiquorum , commonly known as "Imperial Taro", is an edible vegetable in many tropical and subtropical regions of the world. This study with the aim of evaluating the potential of C. antiquorum var. esculenta as a functional food with a depigmenting effect resulted in the identification of a new sesquilignan, named colocasinol A (1), and a new acyclic phenylpropane lignanamide, named cis-grossamide K (2), together with 10 known compounds (3-12). The identification and structural elucidation of these compounds were based on 1D and 2D nuclear magnetic resonance (NMR) spectroscopic data analysis as well as high-resolution fast atom bombardment mass spectrometry (FABMS) and electron impact mass spectrometry (EIMS). Quantitation of the melanin contents and cell viability in murine melanocyte melan-a cells was used to assess the antimelanogenic activities of the isolated compounds. Among them, cis-grossamide K (2), isoamericanol A (3), americanol A (4), 2-hydroxy-3,2'-dimethoxy-4'-(2,3-epoxy-1-hydroxypropyl)-5-(3-hydroxy-1-propenyl)biphenyl (5), and (-)-pinoresinol (6) showed inhibitory effects on melanin production. Compounds 2, 5, and 6 exerted a particularly strong antimelanogenic activity on the cells without high cell toxicity (IC(50) = 54.24, 53.49, and 56.26 microM, and LD(50) = 163.60, 110.23, and >500 microM, respectively).

Structure elucidation and NMR assignments for two xanthone derivatives from a mangrove endophytic fungus (No. ZH19)

The structure elucidations and complete (1)H and (13)C NMR assignments are reported for two new xanthone derivatives: 1,7-dihydroxy-2-methoxy-3-(3-methylbut-2-enyl)-9H-xanthen-9-one (1) and 1-hydroxy-4,7-dimethoxy-6-(3-oxobutyl)-9H-xanthen-9-one (2). Both of these secondary metabolites were isolated from the fermentation medium of a mangrove endophytic fungus (No. ZH19). High-resolution electron impact mass spectrometry (HREIMS), Fourier transform infrared (FT-IR) absorption spectrometry, and NMR experiments including gCOSY, gHMQC, and gHMBC were used for the determination of the structures and NMR spectral assignments. Preliminary pharmacological test showed that compounds (1) and (2) inhibited KB cells with IC(50) values of 20 and 35 micromol/ml, and KB(V)200 cells with IC(50) values of 30 and 41 micromol/ml, respectively.

ANALYSIS OF ELECTRON-IMPACT EXCITATION AND EMISSION OF THE np σ 1 Σ + u AND np π 1 Π u RYDBERG SERIES OF H 2

Calculated and recently measured photoabsorption transition probabilities of the H2 npσ1Σ+u and npπ1Πu − X1Σ+g band systems have been examined with high-resolution (Δλ = 95–115 mÅ) electron-impact induced emission spectra obtained previously by Jonin et al. and Liu et al. When localized rovibronic coupling is insignificant, transition probabilities calculated with the adiabatic approximation are found to be generally consistent with experiment. However, in the presence of significant coupling, the transition probabilities obtained from a nonadiabatic calculation of B'1Σ+u, D1Π+u, , D'1Π+u, and 5pσ1Σ+u state coupling give better agreement with the experimental spectra. Emission yields obtained by comparison of the calculated and experimental spectra are also consistent with the measured predissociation and autoionization yields. In addition, more accurate excitation and emission cross sections and nonradiative yields have been obtained for a number of the npσ1Σ+u and npπ1Πu states. The results obtained in the present investigation lead to a significantly more accurate calibration of the Cassini UVIS instrument and laboratory spectrometers in the range 790–920 Å. They are also an important step toward an accurate model of extreme ultraviolet H2 auroral and dayglow emissions in the outer planet atmospheres.

Structure elucidation and NMR assignments for two amide alkaloids from a Mangrove endophytic Fungus (No. ZZF‐22)

The structure elucidations and complete (1)H and (13)C NMR assignments are reported for two new natural products: 3-benzylidene-8,8a-dihydroxy-2-methyl-hexahydro-pyrrolo[1,2-a]pyrazine-1,4-dione(1) and 4-hydroxy-6-(hydroxy-phenyl-methyl)-N-(3-methyl-butyryl)-nicotinamide (2). Both of these secondary metabolites were isolated from the fermentation medium of a Mangrove endophytic fungus. High resolution electron impact mass spectrometry (HREIMS), FT-IR Spectroscopy and NMR experiments including gCOSY, gHMQC, gHMBC and NOE were used for determination of the structures and assignments of the amide alkaloids.