Search

Isomerized amino acid residues have been identified in many peptides extracted from tissues or excretions of humans and animals. These isomerized residues can play key roles by affecting biological activity or by exerting an influence on the process of aging. Isomerization occurs spontaneously and does not result in a mass shift. Thus, identifying and localizing isomerized residues in biological samples is challenging. Herein, we introduce a fast and efficient method using tandem mass spectrometry (MS) to locate isomerized residues in peptides. Although MS2 spectra are useful for identifying peptides that contain an isomerized residue, they cannot reliably localize isomerization sites. We show that this limitation can be overcome by utilizing MS3 experiments to further evaluate each fragment ion from the MS2 stage. Comparison at the MS3 level, utilizing statistical analyses, reveals which MS2 fragments differ between samples and, therefore, must contain the isomerized sites. The approach is similar to previous work relying on ion mobility to discriminate MS2 product ions by collision cross-section. The MS3 approach can be implemented using either ion-trap or beam-type collisional activation and is compatible with the quantification of isomer mixtures when coupled to a calibration curve. The method can also be implemented in combination with liquid chromatography in a targeted approach. Enabling the identification and localization of isomerized residues in peptides with an MS-only methodology will expand accessibility to this important information.

Doxepin is an antihistamine and tricyclic antidepressant that binds to the histamine H1 receptor (H1R) with high affinity. Doxepin is an 85:15 mixture of the E‐ and Z‐isomers. The Z‐isomer is well known to be more effective than the E‐isomer, whereas based on the crystal structure of the H1R/doxepin complex, the hydroxyl group of Thr1123.37 is close enough to form a hydrogen bond with the oxygen atom of the E‐isomer. The detailed binding characteristics and reasons for the differences remain unclear. In this study, we analyzed doxepin isomers bound to the receptor following extraction from a purified H1R protein complexed with doxepin. The ratio of the E‐ and Z‐isomers bound to wild‐type (WT) H1R was 55:45, indicating that the Z‐isomer was bound to WT H1R with an approximately 5.2‐fold higher affinity than the E‐isomer. For the T1123.37V mutant, the E/Z ratio was 89:11, indicating that both isomers have similar affinities. Free energy calculations using molecular dynamics (MD) simulations also reproduced the experimental results of the relative binding free energy differences between the isomers for WT and T1123.37V. Furthermore, MD simulations revealed that the hydroxyl group of T1123.37 did not form hydrogen bonds with the E‐isomer, but with the adjacent residues in the binding pocket. Analysis of the receptor‐bound doxepin and MD simulations suggested that the hydroxyl group of T1123.37 contributes to the formation of a chemical environment in the binding pocket, which is slightly more favorable for the Z‐isomer without hydrogen bonding with doxepin. [ABSTRACT FROM AUTHOR]

Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

ABSTRACT Two isomeric homoleptic Ir(III) complexes with pyridinopyridazine derivative ligands were prepared first. Due to its stronger intramolecular hydrogen bonding and intermolecular interactions, complex IrPPM has a higher decomposition temperature (5% weight loss) of 387°C than IrPPP (354°C). They have similar UV–Vis absorption and photoluminescence spectra in CH2Cl2 solution with photoluminescence peaks around 635–636 nm. However, the emission peak of IrPPM in neat powder obviously red‐shifted to 652 nm, and that of IrPPP blue‐shifted to 626 nm. Simultaneously, complex IrPPM has a lower photoluminescence quantum yield of 0.3 than IrPPP (0.5). Efficient saturated red OLED devices are developed with Commission Internationale de L'Eclairage color coordinates of (0.67, 0.32) and (0.66, 0.32), respectively. The maximum external quantum efficiencies of both devices exceed 11%. These results demonstrate the great potential of pyridinopyridazine derivatives for developing new iridium complexes for OLED applications. [ABSTRACT FROM AUTHOR]

Fe3(CO)12 reacted with azadiethylthiols afforded [Fe2(μ‐S(CH2)2NR(CH2)2S)(CO)6]2 (R = nPr, 1A; iPr, 2A). Structure analysis revealed that 1A features the anti‐(a,e,a,e) configuration, while its iso‐propyl 2A adopts the syn‐(a,e,a,e) arrangement. NMR measurements at room temperature confirmed this structure, showing distinct signals for 2 NCH2 and 2 SCH2 methylene groups. Acid treatment of 1–2 yielded N‐protonated species (1A–H, 2A–H), maintaining the anti‐(a,e,a,e) configuration. Isolation of 1B–H revealed both the syn‐(a,e,e,a) and anti‐(a,e,e,a) configuration by X‐ray single‐crystallography. Protonation of 1A–H induced downfield shifts in methylene proton signals, with NH hydrogen recorded at 6.96 ppm. Furthermore, 1B–H displays similar NMR behavior, indicating the coexistence of two isomeric molecules of 1B–H, syn‐(a,e,e,a) and anti‐(a,e,e,a), which is consistent with the crystallographic results. Moreover, ion mobility‐mass spectrometry (IM‐MS) is harnessed for the swift identification and differentiation of these isomeric complexes in solution. By leveraging accurate mass measurements and MS/MS analyses, the molecular formula and constituents are validated. The sample mobility enables straightforward characterization of 1A, 1B, and 2A in relation to their stereo‐ and regio‐configurations, obviating the need for extensive time or sample quantities. Integration of findings from X‐ray crystallography, NMR, and IM‐MS furnishes precise and comprehensive structural insights into the coordination complexes. [ABSTRACT FROM AUTHOR]

Mass spectrometry (MS) is a versatile analytical tool used in various fields such as biochemistry, pharmacology, omics, and clinical analysis for determining and quantifying compounds based on their molecular mass and structure through the mass-to-charge ratio. While MS offers high specificity and selectivity, it encounters challenges including matrix effects, in-source fragmentation, and other interferences caused by natural isotopic abundance, as well as isomeric and isobaric compounds. These challenges can impede accurate qualitative and quantitative analysis. Visual aids such as graphical illustrations can help elucidate the chemical differences and similarities among isotopes, isomers, and isobaric compounds.

The technique for investigating isomeric states of nuclei with a large values of energy and total momentum created in the neutron capture reaction has been developed. The technique is based on the spectrometry of multiplicity, energy, and time of registration of instantaneous and delayed gamma cascades of isomer occupancy and decay, respectively. The technique was tested in measurements of the isomeric ratio of the 183W level with energy Eiz = 1.285 MeV with total moment Jπiz = 4-, 5- and lifetime Tiz = 8.2 μs in the neutron absorption reaction, which is equal to αiz = (4.7 ± 0.9)⋅10-3. At large values of the efficiency of registration of acts of settlement and decay of the isomer (0.6 - 0.8), the level of the corresponding background of the spectrometer is only 3.5⋅10-4 s-1. At the countable load at the spectrometer input ∼1.5⋅103 s-1, the expected sensitivity of determining the isomeric ratio in measurements with the mono isotope of the sample is αiz ∼(0.3 ± 1.0)⋅10-4.

The ginsenoside isomers were analyzed and distinguished by using inlet ionization-high resolution mass spectrometry technology under positive and negative ion modes with optimum inlet temperatures. The results showed that under the full scanning mode of positive and negative ion modes with the optimum experimental temperature, different types of ions were formed according to the characteristics of different numbers of polymers formed by isomeric monomers of ginsenoside, and the identification of ginsenoside isomers was realized. For the identification of ginsenoside CK and Rh2, there was no obvious difference in their MS spectra under positive ion mode. However, under negative ion mode with the inlet temperature of 200 ℃, ginsenoside CK tended to form polymers of [M+Cl]－, Rh2 tended to form polymers of [M+COOH]－, and the number of polymers of CK was significantly higher than that of Rh2. For the identification of ginsenoside Rb2 and Rc, under positive ion mode with the inlet temperature of 200 ℃, ginsenoside Rb2 and Rc could produce polymers of [M+Na]+, but the polymers peak intensity of Rb2 was significantly higher than that of Rc. Under negative ion mode with the inlet temperature of 200 ℃, Rb2 tended to form polymers of [M+Cl]－, and Rc tended to form polymers of [M+COOH]－. For the identification of ginsenoside Rg1 and Rf, there was no obvious difference in their MS spectra under the positive ion mode. Under negative ion mode with the inlet temperature of 200 ℃, Rg1 and Rf tended to form polymers of [M+Cl]－ and [M−H]−, respectively. In this study, the three pairs of isomers in ginsenosides were basically identified by using the full MS scanning method and the control of the mass spectrometry inlet temperature. The experimental method is simple, fast, and has the characteristics of low consumption. This study confirms that the entrance ionization mass spectrometry technique can provide a theoretical reference for the rapid discrimination and identification of ginsenoside isomers.

Polyhedral oligomeric silsesquioxane (POSS) is an organic‐inorganic hybrid molecule with two structural variations, closed‐ and open‐cage configurations, referred to as completely condensed POSS (CC‐POSS) and corner‐opened POSS (CO‐POSS), respectively. In this study, we synthesized 12 dimers by combining CC‐ and CO‐POSS variants decorated with isobutyl or phenyl substituents to explore their structure‐property relationships. The choice of substituents, both at the cage vertices and open sites, significantly affected the thermal and optical properties of the materials. Modifying the substituents on CO‐ and CC‐POSS, which are isomers, led to significant alterations in the material properties. Notably, isomer‐bearing carbazole substituents exhibited a substantially higher quantum yield (0.32) than its counterpart isomer (0.13), underscoring the crucial role of structural nuances in determining material performance. These results offer valuable insights for the design of novel silsesquioxane‐based materials. [ABSTRACT FROM AUTHOR]

A series of carboxylated carbosilane surfactants with methyl, ethyl, branching CH3, phenyl, and cyclohexyl (Me‐Si2C‐COONa, Et‐Si2C‐COONa, Si2C‐La‐COONa, Ph‐Si2C‐COONa, and Cy‐Si2C‐COONa) were prepared. The effect of isomer and steric hindrance on their micellization in aqueous solution was investigated by surface tension, conductivity, transmission electron microscopy (TEM) and dynamic light scattering (DLS). Si2C‐La‐COONa with branching CH3 shows a lower γCMC value and higher the CMC value compared with Et‐Si2C‐COONa. Cy‐Si2C‐COONa with cyclohexyl (41.6 mN m−1) and Ph‐Si2C‐COONa with phenyl (43.9 mN m−1) have larger γCMC values due to the distinct steric hindrance and hydrophobicity. In aqueous solution, the aggregation behavior of Si2C‐La‐COONa, Cy‐Si2C‐COONa, and Ph‐Si2C‐COONa is enthalpy‐driven. However, the micellization process of Me‐Si2C‐COONa and Et‐Si2C‐COONa is governed by the enthalpy‐driven at high temperature and entropy‐driven at low temperature. DLS and TEM results indicate that the carboxylated carbosilane surfactants can self‐assemble into aggregate with hydrodynamic diameters of 50–400 nm. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) possess a considerable number of beneficial features for latent applications in biotargeted drugs, electronic transistors, and encrypted information. The synthesis of fluorescent carbon dots has become a trend in contemporary research, especially in the field of controllable multicolor fluorescent carbon dots. In this study, an elementary one-step hydrothermal method was employed to synthesize the multicolor fluorescent carbon dots by co-doping unique phenylenediamine isomers (o-PD, m-PD, and p-PD) with B and P elements, which under 365 nm UV light exhibited signs of lavender-color, grass-color, and tangerine-color fluorescence, respectively. Further investigations reveal the distinctness in the polymerization, surface-specific functional groups, and graphite N content of the multicolor CDs, which may be the chief factor regarding the different optical behaviors of the multicolor CDs. This new work offers a route for the exploration of multicolor CDs using B/P co-doping and suggests great potential in the field of optical materials, important information encryption, and commercial anticounterfeiting labels. [ABSTRACT FROM AUTHOR]

Abstract: The ginsenoside isomers were analyzed and distinguished by using inlet ionization-high resolution mass spectrometry technology under positive and negative ion modes with optimum inlet temperatures. The results showed that under the full scanning mode of positive and negative ion modes with the optimum experimental temperature, different types of ions were formed according to the characteristics of different numbers of polymers formed by isomeric monomers of ginsenoside, and the identification of ginsenoside isomers was realized. For the identification of ginsenoside CK and Rh2, there was no obvious difference in their MS spectra under positive ion mode. However, under negative ion mode with the inlet temperature of 200 ℃, ginsenoside CK tended to form polymers of [M+Cl]－, Rh2 tended to form polymers of [M+COOH]－, and the number of polymers of CK was significantly higher than that of Rh2. For the identification of ginsenoside Rb2 and Rc, under positive ion mode with the inlet temperature of 200 ℃, ginsenoside Rb2 and Rc could produce polymers of [M+Na]+, but the polymers peak intensity of Rb2 was significantly higher than that of Rc. Under negative ion mode with the inlet temperature of 200 ℃, Rb2 tended to form polymers of [M+Cl]－, and Rc tended to form polymers of [M+COOH]－. For the identification of ginsenoside Rg1 and Rf, there was no obvious difference in their MS spectra under the positive ion mode. Under negative ion mode with the inlet temperature of 200 ℃, Rg1 and Rf tended to form polymers of [M+Cl]－ and [M−H]−, respectively. In this study, the three pairs of isomers in ginsenosides were basically identified by using the full MS scanning method and the control of the mass spectrometry inlet temperature. The experimental method is simple, fast, and has the characteristics of low consumption. This study confirms that the entrance ionization mass spectrometry technique can provide a theoretical reference for the rapid discrimination and identification of ginsenoside isomers. [ABSTRACT FROM AUTHOR]

In this paper, we describe the teaching material and practice of early STEAM education for junior high school students using graph theory. The classification problem of structural isomers of organic compounds as a teaching material for mathematics was considered. By regarding chemical molecules as estimate and considering the differences of mathematical property, we can consider the difference of isomers. We developed and practiced a mathematical teaching material for Junior high school students to discover the difference of molecules by themselves using graphs and determine the number of isomers. The result of the questionnaire suggested that this material was effective in generating interest in science and mathematics. [ABSTRACT FROM AUTHOR]

To date, the systematic summarization and comprehensive review of analysis, distribution, migration, and degradation of chiral antibiotics in the vadose zone are limited. This review indicates that the physicochemical characteristics of chiral antibiotics are quite different, for instance, the solubility and octanol-water partition coefficient (lg Kow) of S-gemifloxacin are 301 times and 9.8 times larger than the values of R-gemifloxacin, which will affect their migration and degradation in the environment. High performance liquid chromatography with chiral column and chiral ligand-exchange chromatography are the common methods on the chiral antibiotics analysis. The concentrations of chiral antibiotics in soils, waters, and agricultural products in China and abroad are reported; flumequine, lomefloxacin and ofloxacin are the most common antibiotics. The adsorption rate and partition coefficient (Kd) of chiral antibiotics during their adsorption on minerals and microplastics are different, especially in the presence of natural organic matter (NOM); however, there is no relationship among the various types of chiral antibiotics. Chiral antibiotics can be complexed with the common cations, and their stability constants are quite different in the groundwater, for instance, the stability constant of Mg2+-levofloxacin is 22.9 times larger than that of Mg2+-ofloxacin. During the biodegradation process, the degradability and rate of chiral antibiotics are also different. Additionally, the chiral antibiotics can be transformed reciprocally. In this review, the distribution, migration, and degradation of chiral antibiotics in the vadose zone are investigated, which is beneficial to the study on the chiral antibiotics in the groundwater. As to the environmental fate of chiral antibiotics in the vadose zone, the following researches are recommended: (1) the resolution, analysis, toxicology, and standard establishment of chiral antibiotics; (2) the investigation, migration, and degradation of multiple chiral antibiotics; (3) the environmental processes of chiral antibiotics in the multi-interface.

Ultra-intense laser-plasma wakefield accelerator possess several superior properties compared with the traditional radio-frequency accelerators. These characteristics include femtosecond duration, micro-source size, and ultra-dense beam density, result in highly advantageous for various important applications. In this paper, we reviewed the generation of ultra-intense and high charge electron beam based on laser-plasma acceleration and its nuclear applications in Shanghai Jiao Tong University, including the production of 10 s nC charge beams, the generation of ultra-high flux neutron source on the order of 1019 n/cm2/s, and the excitation of nuclear isomers with the peak efficiency on the order of 1015 particle/s. This laser driving ultra-dense electron source, in conjunction with the plasma environment, presents immense potential in addressing critical problems in astrophysics, and facilitating various nuclear applications. Based on above progress in nuclear astrophysics, a new research plateform about laboratory astrophysics with a 2.5 PW laser will be constructed in TDLI institute.

The tree Eucalyptus camaldulensis is a ubiquitous member of the Eucalyptus genus, which includes several hundred species. Despite the extensive sequencing and assembly of nuclear genomes from various eucalypts, the genus has only one fully annotated and complete mitochondrial genome (mitogenome). Plant mitochondria are characterized by dynamic genomic rearrangements, facilitated by repeat content, a feature that has hindered the assembly of plant mitogenomes. This complexity is evident in the paucity of available mitogenomes. This study, to the best of our knowledge, presents the first E. camaldulensis mitogenome. Our findings suggest the presence of multiple isomeric forms of the E. camaldulensis mitogenome and provide novel insights into minor rearrangements triggered by nested repeat sequences. A comparative sequence analysis of the E. camaldulensis and E. grandis mitogenomes unveils evolutionary changes between the two genomes. A significant divergence is the evolution of a large repeat sequence, which may have contributed to the differences observed between the two genomes. The largest repeat sequences in the E. camaldulensis mitogenome align well with significant yet unexplained structural variations in the E. grandis mitogenome, highlighting the adaptability of repeat sequences in plant mitogenomes. [ABSTRACT FROM AUTHOR]

This study aimed to explore the isomer-specific, sex-specific, and joint associations of PFAS and red blood cell indices. We used data of 1,238 adults from the Isomers of C8 Health Project in China. Associations of PFAS isomers and red blood cell indices were explored using multiple linear regression models, Bayesian Kernel Machine Regression models and subgroup analysis across sex. We found that serum concentration of linear (n-) and branched (Br-) isomers of perfluorooctane sulfonate (PFOS) and perfluorohexanesulfonic acid (PFHxS) were significantly associated with red blood cell indices in single-pollutant models, with stronger associations observed for n-PFHxS than Br-PFHxS, in women than in men. For instance, the estimated percentage change in hemoglobin concentration for n-PFHxS (3.65%; 95% CI: 2.95%, 4.34%) was larger than that for Br-PFHxS (0.96%; 95% CI: 0.52%, 1.40%). The estimated percentage change in red blood cell count for n-PFHxS in women (2.55%; 95% CI: 1.81%, 3.28%) was significantly higher than that in men (0.12%; 95% CI: −1.04%, 1.29%) (Pinter < 0.001). Similarly, sex-specific positive association of PFAS mixture and outcomes was observed. Therefore, the structure, susceptive population, and joint effect of PFAS isomers should be taken into consideration when evaluating the health risk of chemicals. [ABSTRACT FROM AUTHOR]

The technique for investigating isomeric states of nuclei with a large values of energy value and total momentum created in the neutron capture reaction has been developed. The technique is based on the spectrometry of multiplicity, energy, and time of registration of instantaneous and delayed gamma cascades of isomer occupancy and decay, respectively. The technique was tested in measurements of the isomeric ratio of the 183W level with energy Eiz = 1.285 MeV with total moment 4,5 Jπiz = and lifetime Tiz = 8.2 μs in the neutron absorption reaction, which is equal to αiz = (4.7 ± 0.9)·10−3. At large values of the efficiency of registration of acts of settlement and decay of the isomer (0.6 - 0.8), the level of the corresponding background of the spectrometer is only 3.5·10−4 s−1 . At the countable load at the spectrometer input ~1.5·10³ s −1, the expected sensitivity of determining the isomeric ratio in measurements with the mono isotope of the sample is αiz ~(0.3 ± 1.0)·10−4 . [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology & Engineering Geology / Shuiwendizhi Gongchengdizhi is the property of Hydrogeology & Engineering Geology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The substitution of heteroatoms and the expansion of π‐conjugated units have significant effects on the photoelectric properties of polycyclic aromatic hydrocarbons (PAHs). In this study, based on the experimental molecule PBC, 10 acene derivatives containing the pyrrole group were designed by three strategies: (1) changing the connection position of the pyrrole group, (2) exchanging the position of the N atom, and (3) increasing the length of the π‐linker. Density functional theory (DFT) was used to optimize the molecular geometric structure. Time‐dependent density functional theory (TD‐DFT) was used to calculate the relevant parameters of the excited states. The results show that both of the pyrrole group and the N atom in the para‐position, and the addition of the π‐linker can reduce the energy gap, cause redshift of the linear absorption peak, and increase the two photon absorption (TPA) cross‐section. The analyses of the charge density difference (CDD) and the charge‐transfer matrix (CTM) proved that the electron transfer is mainly concentrated in the π‐linker. Moreover, the participation of the multi‐ring skeleton on both sides decreases gradually with the increase of the length of the π‐linker. The length of the π‐linker changes the dominant transition channel and intramolecular charge‐transfer (ICT) characteristics of TPA, thus affecting the transition dipole moments and nonlinear absorption properties. The second hyperpolarizability of the designed molecule PBI5‐p5 is also significantly superior to that of similar materials reported. It is expected that the above molecular design strategies and comprehensive analysis of nonlinear optical (NLO) properties could provide theoretical support for the research on acene derivatives. [ABSTRACT FROM AUTHOR]

The systematization of possible ways to form C28 and C30 fullerene isomers has been completed in this work. An additional confirmation was obtained that fullerenes created by incorporating dimers into the initial structure had a minimum energy. Two other methods for the formation of new fullerenes were also considered, namely, the connection of two domes with the same symmetry and that of fullerenes with compatible symmetry. The symmetry order of the studied fullerenes varied from the second to the seventh ones. A collaboration analysis of the formation energy values and geometric simulation results allowed us to draw conclusions about the structural changes in the resulting fullerenes.

In situ separation and visualization of synthetic and naturally occurring isomers from heterogeneous plant tissues, especially when they share similar molecular structures, are a challenging task. In this study, we combined the ion mobility separation with desorption electrospray ionization mass spectrometry imaging (DESI-IM-MSI) to achieve a direct separation and visualization of two synthetic auxin derivatives, auxinole and its structural isomer 4pTb-MeIAA, as well as endogenous auxins from Arabidopsis samples. Distinct distribution of these synthetic isomers and endogenous auxins in Arabidopsis primary roots and hypocotyls was achieved in the same imaging analysis from both individually treated and cotreated samples. We also observed putative metabolites of synthetic auxin derivatives, i.e. auxinole amino acid conjugates and hydrolysed 4pTb-MeIAA product — 4pTb-IAA, based on their unique drifting ion intensity patterns. Furthermore, DESI-IM-MSI-revealed abundance of endogenous auxins and synthetic isomers was validated by liquid chromatography–mass spectrometry (LC-MS). Our results demonstrate that DESI-IM-MSI could be used as a robust technique for detecting endogenous and exogenous isomers and provide a spatiotemporal evaluation of hormonomics profiles in plants. [ABSTRACT FROM AUTHOR]

The physical properties of silsesquioxane materials are commonly controlled by varying the proportion of silane coupling agents with different substituents. In contrast, with cage silsesquioxanes (polyhedral oligomeric silsesquioxane, POSS) that allow for precise molecular design, the material properties can be controlled by isomers, similar to organic materials. In this study, we synthesized polyurethanes with corner‐opened POSS (CO‐POSS) and completely condensed POSS (CC‐POSS) in the main and side chains, respectively. For the substituents on POSS, we used a combination of phenyl and isobutyl groups and investigated their effects on the physical properties by changing this combination. Notably, the thermal and mechanical properties changed in polymers where the substituents of CO‐POSS (main chain) and CC‐POSS (side chain) were interchanged. This demonstrates that the isomeric structure significantly affects the properties of silsesquioxane‐based materials and provides important design guidelines for these materials. [ABSTRACT FROM AUTHOR]

In toxic substance detection devices based on ion mobility spectrometry with atmospheric pressure chemical ionization, hydrated ammonium (H2O)n is increasingly used as a reagent ion instead of the commonly used hydrated hydroxonium H3O+(H2O)n ion and ions preceding and accompanying its formation. The use of hydrated ammonium makes it possible to increase the specificity of devices in the presence of such problematic interferences as exhaust gases of internal combustion engines and motor fuel vapors. In this paper, the mechanism of increasing specificity in the presence of alkanes, significantly predominant in these interferences, is justified. In the absence of ammonia, which is used to produce hydrated ammonium, the chemical ionization of alkanes occurs as a result of fast exergonic reactions with ions preceding ( , , , H2O+ , and H3O+) and accompanying (NO+ and NO+(H2O)) the formation of hydrated hydroxonium. When ammonia is added, these ions react with it and are almost completely consumed in fast exergonic reactions. Thereby ammonia suppresses the chemical ionization of alkanes by precursor and accompanying ions. The direct chemical ionization of alkanes with the help of hydrated ammonium does not occur due to the endergonicity of the reactions and the almost complete shift of their equilibrium towards the formation of the initial reagents. As a result, the devices do not give false-positive signals when exposed to alkanes. In addition, the devices do not produce false-negative signals when analytes are detected in a mixture with alkanes, since hydrated ammonium is practically not consumed in reactions with alkanes. [ABSTRACT FROM AUTHOR]

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on the safety of a change of specifications of the novel food (NF) oleoresin from Haematococcus pluvialis containing astaxanthin (ATX) pursuant to Regulation (EU) 2015/2283. The NF is already authorised as ingredient for the use in food supplements as defined in Directive 2002/46EC in accordance to Regulation (EU) 2017/2470. The NF concerns an oleoresin which contains ~ 10% ATX, obtained by supercritical CO2 extraction of the homogenised and dried biomass of cultivated H. pluvialis. This NF has been assessed by the Panel in 2014. With the present dossier, the applicant proposed to lower the minimum specification limits for protein and ATX monoesters for the NF, and to increase the maximum specification limit for the relative amount of ATX diesters in total ATX. An increase of the maximum specification limit for the 9‐cis isomer is also applied for. Although the data are limited regarding bioavailability and distribution in humans of these three naturally occurring ATX isomers, the available in vitro and in vivo data suggest that the 13‐cis rather than the 9‐cis ATX is selectively absorbed, i.e. has a higher bioavailability and/or possibly emerges from isomerisation of all‐trans ATX. The Panel notes that the toxicity of the individual ATX isomers has not been studied individually. However, the ADI of 0.2 mg/kg, which was established for synthetic ATX and ATX from H. pluvialis, applies also for ATX in the oleoresin from H. pluvialis with the proposed changes of specifications. The Panel concludes that the NF, oleoresin from H. pluvialis containing ATX, is safe with the proposed specification limits. [ABSTRACT FROM AUTHOR]

BackgroundPrevious research indicated that isomers and alternatives of per- and polyfluoroalkyl substances (PFAS) probably disturb glucose metabolism; however, current epidemiological evidence on the associations of PFAS with fasting blood glucose is inconsistent. Besides, studies on the joint association of multiple components of PFAS and fasting blood glucose as well as the key component are scarce. ObjectiveTo evaluate the associations of PFAS isomers and alternatives with fasting blood glucose and their joint effects, as well as identify the key component among population without glucose metabolism problems. MethodsWe selected 923 adults without glucose metabolism problems or missing data from the Isomers of C8 Health Project in China (2015—2016). Serum PFAS isomers and alternatives and fasting blood glucose were measured using ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) and automatic biochemical analyzer. We applied multiple linear regression to explore the associations of 16 pollutants which were detected among over 80% participants with fasting blood glucose. Meanwhile, we utilized qgcomp and Bayesian kernel machine regression (BKMR) models to explore the joint effects of PFAS isomers and alternatives mixture on target outcome indicators and identify the key component. ResultsThe average age among the 923 participants in this study was (62.4±13.8) years old, including 472 men (51.1%) and 451 women (48.9%). Among selected PFAS isomers and alternatives, the highest serum concentration was ∑3+4+5m-PFOS (perfluoro-3/4/5-methylheptanesulfonate) with a median concentration of 10.20 ng·mL−1. The concentrations of linear perfluorooctane sulfonate (n-PFOS, 9.61 ng·mL−1), perfluorooctanoic acid (PFOA, 4.55 ng·mL−1), linear perfluorohexane sulfonic acid (n-PFHxS, 2.48 ng·mL−1), 6:2 chlorinated polyfluorinated ethersulfonic acid (6:2 Cl-PFESA, 1.90 ng·mL−1), perfluoro-6-methylheptanesulfonate (iso-PFOS, 1.85 ng·mL−1), perfluorobutanoic acid (PFBA, 1.81 ng·mL−1), perfluorinated n-nonanoic acid (PFNA, 1.39 ng·mL−1), and perfluoro-1-methylheptanesulfonate (1m-PFOS, 1.27 ng·mL−1) were higher than 1.00 ng·mL−1. After being adjusted for selected confounders, PFAS isomers and alternatives were positively associated with fasting blood glucose. With 1 ln unit concentration increment of 6:2 Cl-PFESA and PFNA, the estimated changes of fasting blood glucose were 0.18 (95%CI: 0.13, 0.23) mmol·L−1 and 0.24 (95%CI: 0.18, 0.30) mmol·L−1, respectively. The multi-pollutant models indicated a joint association of PFAS isomers and alternatives mixture with fasting blood glucose. The BKMR models reveals that as the quantiles of mixture elevated from the 50th to the 75th percentile, the values of fasting blood glucose increased 0.25 (95%CI: 0.21, 0.30) mmol·L−1, and the posterior inclusion probability of PFNA was 0.92, implying that PFNA was the key component. ConclusionPFAS isomers and alternatives are positively associated with fasting blood glucose. PFNA is the key component of the joint association.

Carbon dots (CDs) possess a considerable number of beneficial features for latent applications in biotargeted drugs, electronic transistors, and encrypted information. The synthesis of fluorescent carbon dots has become a trend in contemporary research, especially in the field of controllable multicolor fluorescent carbon dots. In this study, an elementary one-step hydrothermal method was employed to synthesize the multicolor fluorescent carbon dots by co-doping unique phenylenediamine isomers (o-PD, m-PD, and p-PD) with B and P elements, which under 365 nm UV light exhibited signs of lavender-color, grass-color, and tangerine-color fluorescence, respectively. Further investigations reveal the distinctness in the polymerization, surface-specific functional groups, and graphite N content of the multicolor CDs, which may be the chief factor regarding the different optical behaviors of the multicolor CDs. This new work offers a route for the exploration of multicolor CDs using B/P co-doping and suggests great potential in the field of optical materials, important information encryption, and commercial anticounterfeiting labels.

Synthetic cathinones, the designer analogs of the naturally occurring cathinone found in Khat, largely entered the recreational drug market at the end of the 2000s. They are a large class of new psychoactive substances (NPS) often used as substitutes for cocaine, which may cause psychostimulant and hallucinogenic effects and a number of fatalities worldwide. N-Ethylpentylone, one of the most famous synthetic cathinones on the clandestine market, was controlled in China since September 1, 2018. Recently, three uncontrolled isomers of N-ethylpentylone, namely hexylone, dipentylone and N-propylbutylone, were identified in the suspected samples. In order to investigate the mass fragmentation characteristics of synthetic cathinones with similar chemical structures, the four isomers were analyzed using gas chromatography-Orbitrap mass spectrometry (GC-Orbitrap-MS) and ultra high performance liquid chromatography-quadrupole time of flight-mass spectrometry (UPLC-QTOF-MS). High-resolution mass spectra were obtained by electron impact (EI) and electrospray ionization-collision induced dissociation (ESI-CID), and the structures and fragmentation pathways of main product ions were deduced. Under the EI mode, four isomers presented similar mass spectra with same base peak ion C6H14N+, which was originated from the α-cleavage of the C—N bond, the dominant fragmentation pathway of all synthetic cathinones. C8H5O3+ and C7H5O2+, the characteristic ions of cathinones with methylenedioxy substituted phenyl ring in the molecular structure, were also observed for all of them. However, there were variances in the low m/z ions generated by further cleavage of C6H14N+. Under the ESI-CID mode, the mass spectra were significantly different from each other, hence the alkyl substitution at different positions could be determined through the fragment ions generated by loss of H2O, amino groups and other groups from ［M+H］+. By investigating the mass spectrometric characteristics of the four isomers, their key distinguishing features were summarized, which provided a reference for the identification of synthetic cathinone, especially the substances with similar chemical structures.

Ceiba pentandra (L.) Gaertn. (Bombacaceae) is popular for the quality of its wood. However, its leaf, stem bark and root bark have been popular in ethnomedicine and, apart from the inflorescence, have been subject of extensive phytochemical investigations. In this study, two compounds were isolated from the crude methanol extract of the inflorescence. Through data from UV, NMR, MS, electrochemical studies, differential scanning calorimetry, and thermogravimetric analysis, the structures were elucidated as 3-C-β-d-glucopyranosyl-1,3,6,7-tetrahydroxyxanthone (1) and 2-C-β-d-glucopyranosyl-1,3,6,7-tetrahydroxyxanthone (mangiferin, 2). They were assessed for antioxidant efficacy (DCFDA assay) and for anti-inflammatory efficacy using the lipopolysaccharide (LPS)-induced inflammation model in the RAW 264.7 macrophages (nitrite levels quantified, using Griess Assay, as surrogate for nitric oxide (NO)). Compound 1 (named ceibinin) was established as a novel positional isomer of mangiferin (2). While both 1 and 2 were antioxidant against basal and hydrogen peroxide (100 μM)-induced oxidative stress (6.25 μg/ml abrogated peroxide-induced oxidative stress), ceibinin (1) demonstrated no anti-inflammatory potential, unlike mangiferin (2) which, as previously reported, showed anti-inflammatory effect. Our work reports a positional isomer of mangiferin for the first time in C. pentandra and demonstrates how such isomerism could underlie differences in biological activities and thus the potential for development into therapeutics.

Abstract Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on the safety of a change of specifications of the novel food (NF) oleoresin from Haematococcus pluvialis containing astaxanthin (ATX) pursuant to Regulation (EU) 2015/2283. The NF is already authorised as ingredient for the use in food supplements as defined in Directive 2002/46EC in accordance to Regulation (EU) 2017/2470. The NF concerns an oleoresin which contains ~ 10% ATX, obtained by supercritical CO2 extraction of the homogenised and dried biomass of cultivated H. pluvialis. This NF has been assessed by the Panel in 2014. With the present dossier, the applicant proposed to lower the minimum specification limits for protein and ATX monoesters for the NF, and to increase the maximum specification limit for the relative amount of ATX diesters in total ATX. An increase of the maximum specification limit for the 9‐cis isomer is also applied for. Although the data are limited regarding bioavailability and distribution in humans of these three naturally occurring ATX isomers, the available in vitro and in vivo data suggest that the 13‐cis rather than the 9‐cis ATX is selectively absorbed, i.e. has a higher bioavailability and/or possibly emerges from isomerisation of all‐trans ATX. The Panel notes that the toxicity of the individual ATX isomers has not been studied individually. However, the ADI of 0.2 mg/kg, which was established for synthetic ATX and ATX from H. pluvialis, applies also for ATX in the oleoresin from H. pluvialis with the proposed changes of specifications. The Panel concludes that the NF, oleoresin from H. pluvialis containing ATX, is safe with the proposed specification limits.

The present paper is devoted to elastic potentials and the constitutive equations of mechanics of anisotropic micropolar solids, the kinematics of which can be specified by two independent vector fields: a contravariant field of translational displacements and a contravariant pseudovector field of microrotations of weight +1. The quadratic stress potential is represented by three constitutive tensors of the fourth rank, two of which are pseudotensor in nature and can be assigned weights –2 and –1. Such a solid is completely specified by the 171st micropolar elastic modulus. The main attention is focused on the model of a hemitropic (half-isotropic, demitropic) micropolar elastic solid characterized by nine constitutive constants. The components of the constitutive pseudo-tensor of weight ‒1 turn out to be sensitive to mirror reflection transformations in three-dimensional space. A peculiar algebraic structure of the constitutive tensors of a hemitropic solid, more precisely, their absolute analogues obtained by multiplying by integer powers of a pseudoscalar unity, is studied. It is shown that these tensors can always be constructed from isomers (isomer) of a tensor with constant components (generally insensitive to any transformations of the coordinate system) and one additional fourth-rank tensor constructed, in turn, from the components of the metric tensor. [ABSTRACT FROM AUTHOR]

Hydrofluoroethers (HFEs) represent a new family of promising engineering fluids suitable for technical cleaning and cooling of electronic and magnetic devices or as admixtures in refrigerant blends. Here, we report accurate data for the liquid density at 0.1 MPa and temperatures from 273.15 K to 343.15 K for a series of five HFEs, namely, HFE-7000, HFE-7100, HFE-7200, HFE-7300, and HFE-7500. A highly sensitive vibrating tube densimeter with a borosilicate glass U-tube calibrated according to the procedure by Prokopová et al. (J Chem Thermodyn 173:106855, 2022) provided density data with an expanded uncertainty ( k = 2 ) of 0.13 kg · m - 3 . Influences such as sample degassing, water content, or sample temperature before its dosing into the densimeter are discussed. Thanks to the high sensitivity of the used densimeter, an unexpected shift in the density of different HFE-7100 and HFE-7200 liquid samples was detected. Unlike other HFEs, HFE-7100 and HFE-7200 are mixtures of two hardly separable isomers, which were so far considered having identical thermophysical properties. Utilizing nuclear magnetic resonance spectroscopy, the ratio of n-isomer and iso-isomer was inspected for various liquid samples. In the range of iso-isomer mole fraction from 0.61 to 0.77, the new measurements revealed density differences of more than 5 kg · m - 3 in case of HFE-7100 and of about 3 kg · m - 3 in case of HFE-7200. Consequently, for some applications, the properties of different HFE isomers cannot be considered identical. The Rackett-type correlation for the saturated liquid density was fitted using the new and the literature data. [ABSTRACT FROM AUTHOR]

Copyright of Polymer Materials Science & Engineering is the property of Sichuan University, Polymer Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Commercially available molecular models are elaborately made but generally expensive, which hinders their distribution to all classroom students. Aiming at developing an affordable molecular model, we developed a structure model kit consisting of inexpensive electronic components including transistors and colored light-emitting diodes (LEDs) with a total cost of ca. 2 USD. The structure model kit was designed for building a family of environmental pollutant molecules known as dioxins, in which transistor, white LED, red LED, and yellow LED components are used to represent sp2 carbon, hydrogen, oxygen, and chlorine atoms, respectively. Herein, we report an activity directed to nonchemistry majors studying environmental science and electronic engineering to help them gain insight into the molecular structure of dioxins using the newly developed structure model kit. The activity was well received by many students, some of whom came to understand the relationship between the structure and nomenclature of dioxins, mainly 2,3,7,8-tetrachlorinated dibenzo-p-dioxin (2,3,7,8-TCDD) and its isomers.

The characteristic absorption spectra of three positional isomers of hydroxybenzoic acid are measured using a terahertz time-domain spectroscopy system (THz-TDS) in the 0.6–2.0 THz region at room temperature. Significant differences in their terahertz spectra are discovered, which indicates that THz-TDS is an effective means to identify positional isomers. In order to simulate their spectra, the seven molecular clusters of 2-, 3-, and 4-hydroxybenzoic acid (2-, 3-, and 4-HA) are calculated using the DFT-D3 method. Additionally, the potential energy distribution (PED) method is used to analyze their vibration modes. The analysis indicates that the vibration modes of 2-HA are mainly out-of-plane angle bending and bond angle bend in plane. The vibration modes of 3-HA are mainly bond length stretch and dihedral angle torsion. The vibration modes of 4-HA are mainly bond angle bend in plane and dihedral angle torsion. Interaction region indicator (IRI) analysis is used to visualize the location and type of intermolecular interactions in 2-, 3-, and 4-HA crystals. The results show that the weak interaction type of 2-, 3-, and 4-HA is dominated by van der Waals (vdW) interaction. Therefore, we can confirm that terahertz spectroscopy detection technology can be used as an effective means to identify structural isomers and detect the intermolecular interactions in these crystals. In addition, it can explain the absorption mechanism of terahertz waves interacting with matter. [ABSTRACT FROM AUTHOR]

Context: The synthesis of azobenzene materials is an important aspect of the research in the field of photo-switch materials. It is currently thought that azobenzene molecules exist in the cis and trans form of molecular structure configuration. However, the reaction process allowing for reversible energy switches from trans to cis form is still challenging. Therefore, it is crucial to understand the molecular properties of the azobenzene compounds in order to provide reference for future synthesis and application. Affirmation supporting this perspective has been substantially derived from theoretical results in the isomerization process and whether these molecular structures may affect the electronic properties entirely needs to be confirmed. In this study, I give my effort to understand the molecular structure properties of the cis and trans form of azobenzene molecule from 2-hydroxy-5-methyl-2ʹ-nitroazobenzene (HMNA). Their chemistry phenomena are investigated using the density functional theory (DFT) method. This study shows that the trans-HMNA has a molecular size of 9.0 Å and the cis-HMNA has a molecular size of 6.6 Å. The trans-HMNA exhibits an electronic transition of π → π* type driven by an azo bond, whereas the cis-HMNA exhibits an electronic transition of n → π* type with respect to the non-bonding electrons of oxygen and nitrogen atoms. Therefore, the HMNA mechanism pathway from trans to cis form is feasible to undergo at the inversion pathway in the ground state. Methods: All DFT calculations were performed using the Gaussian Software Packages (Gaussian 09 Revision-A.02 and GaussView 5.0.8). Gaussum 3.0 software was selected to visualize the molecular orbital levels in the density of states diagram. The optimized molecular geometrical parameter was calculated using B3LYP/cc-pVTZ level in the gas phase. TD-DFT with M06-2X/cc-pVTZ level was used as a method for the precise interpretation of excited states in molecular systems. [ABSTRACT FROM AUTHOR]

Synthetic cathinones, the designer analogs of the naturally occurring cathinone found in Khat, largely entered the recreational drug market at the end of the 2000s. They are a large class of new psychoactive substances (NPS) often used as substitutes for cocaine, which may cause psychostimulant and hallucinogenic effects and a number of fatalities worldwide. N-Ethylpentylone, one of the most famous synthetic cathinones on the clandestine market, was controlled in China since September 1, 2018. Recently, three uncontrolled isomers of N-ethylpentylone, namely hexylone, dipentylone and N-propylbutylone, were identified in the suspected samples. In order to investigate the mass fragmentation characteristics of synthetic cathinones with similar chemical structures, the four isomers were analyzed using gas chromatography-Orbitrap mass spectrometry (GC-Orbitrap-MS) and ultra high performance liquid chromatography-quadrupole time of flight-mass spectrometry (UPLC-QTOF-MS). High-resolution mass spectra were obtained by electron impact (EI) and electrospray ionization-collision induced dissociation (ESI-CID), and the structures and fragmentation pathways of main product ions were deduced. Under the EI mode, four isomers presented similar mass spectra with same base peak ion C6H14N+, which was originated from the α-cleavage of the C—N bond, the dominant fragmentation pathway of all synthetic cathinones. C8H5O3+ and C7H5O2+, the characteristic ions of cathinones with methylenedioxy substituted phenyl ring in the molecular structure, were also observed for all of them. However, there were variances in the low m/z ions generated by further cleavage of C6H14N+. Under the ESI-CID mode, the mass spectra were significantly different from each other, hence the alkyl substitution at different positions could be determined through the fragment ions generated by loss of H2O, amino groups and other groups from ［M+H］+. By investigating the mass spectrometric characteristics of the four isomers, their key distinguishing features were summarized, which provided a reference for the identification of synthetic cathinone, especially the substances with similar chemical structures. [ABSTRACT FROM AUTHOR]

Recently, different types of ion mobility techniques have sprung up. Combined with mass spectrometry, the utility of ion mobility spectrometry has been enhanced in metabolomics, natural products, characterization of supramolecular materials, and other research fields. Since small molecule metabolites provide deep insight into the dynamic phenotypes of biological systems and show potential value in disease diagnosis and functional interpretation, in-depth analysis of small molecule metabolites plays a key role in medicine and pharmacy. The potential benefits of ion mobility spectrometry used in chiral recognition of amino acids, structural analysis of glycans, and structural characterization of lipids and steroids have become the specific focus of work. However, small molecule metabolites possess a wide variety of chemical properties, ubiquitous isomerism, and various biological functions, so it is difficult to analyze small molecule metabolites comprehensively. On the other hand, small molecule metabolites with low concentrations usually exist in various complex biological matrices, such as plasma, feces, urine, saliva, sweat, infected tissues or exudates, breath, and breast milk, which pose additional challenges to researchers. Over the last few decades, ion mobility-mass spectrometry (IM-MS) has undergone inordinate growth in instrument development and performance, which has opened a new door to rapidly analyze small molecular metabolites in complex biological matrices. Small molecular metabolites and their isomers can be distinguished and characterized in milliseconds by IM-MS that offer high selectivity and three-dimensional information about them, including mass-charge ratio, collision cross section (CCS), and structural information. The collision cross section can be used as an additional identification basis in targeted and untargeted analyses. In this paper, the main commercial IM-MS instruments were briefly covered. An overview of the latest applications in small molecular metabolites was offered. Additionally, the advantages and shortcomings of IM-MS in the analysis of small molecular metabolites were discussed. And the future application of particular and unknown metabolites by IM-MS in the studies on the biological mechanism and precision medicine was prospected.

Revealing the critical thermodynamic parameters determining the glass formation of substances is of great significance for understanding the glass transition and guiding the composition design of glass‐forming materials. Nevertheless, the direct access to glass‐forming ability (GFA) by thermodynamics for various substances remains to be substantiated. The strategy to seek the fundamental properties of glass formation is explored several decades ago, as pioneered by Angell, arguing that the GFA in isomeric xylenes depends on the low lattice energy manifested by the low melting point. Here, an in‐depth study is advanced using two more isomeric systems. Surprisingly, the results do not constantly support the reported relationship between the melting point and glass formation among isomeric molecules. Instead, molecules with enhanced glass formability are featured by the properties of low melting entropy without exception. Comprehensive studies of isomeric molecules find that the low melting entropy is roughly accompanied by the low melting point, explaining the apparent link between melting point and glass formation. Progressively, the viscosity measurements of the isomers uncover a strong dependence of the melting viscosity on melting entropy. These results emphasize the significance of the melting entropy in governing the glass formability of substances. [ABSTRACT FROM AUTHOR]

Buparvaquone 1a is a predominant anti-protozoal drug, it belongs to the pharmacologically active class of hydroxynaphthoquinones. There are numerous publications on the wide therapeutic applications of 1a, but only a few approaches were reported towards its synthesis. Most of the prior arts report the synthesis from expensive raw materials with low yield, whereas only a few involves the use of readily available and less expensive raw materials with moderate to better yield. The present review work covers the developments on therapeutic applications of 1a along with the synthetic approaches disclosed till date. [ABSTRACT FROM AUTHOR]

A zeolite-based mesostructured (MSU) molecular sieve material was synthesized, characterized, and used in the preparation of Pt (0.6 and 1 wt %) supported catalysts for hydroconversion of n-heptane under the experimental conditions of 300–450°C and 760 mmHg. Samples were characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherm, and NH3-TPD (temperature-programmed deposition) techniques. The activity test shows that catalysts have good activity and selectivity for isomerization reaction. Also, increasing metal sites, selectivity tends to the production of aromatization reaction in the heterogeneous catalytic process. Based on experimental results, a kinetic model of this reaction was carried out. Based on other publications and combining the examined features, a network of the reaction was proposed. It can be claimed that the results of converging the feed from the kinetic model are in good agreement with the experimental results. Some of the superiorities of this model compared to other models are the determination of kinetics parameters, source of isomers, aromatic, and cracked products distinctly with emphasis on the effect of site activity and residence time over metal-acid sites. [ABSTRACT FROM AUTHOR]

π-Extended pyrene compounds possess remarkable luminescent and semiconducting properties and are being intensively investigated as electroluminescent materials for potential uses in organic light-emitting diodes, transistors, and solar cells. Here, the synthesis of two sets of pyrene-containing π-conjugated polyaromatic regioisomers, namely 2,3,10,11,14,15,20,21-octaalkyloxypentabenzo[a,c,m,o,rst]pentaphene (BBPn) and 2,3,6,7,13,14,17,18-octaalkyloxydibenzo[j,tuv]phenanthro [9,10-b]picene (DBPn), is reported. They were obtained using the Suzuki–Miyaura cross-coupling in tandem with Scholl oxidative cyclodehydrogenation reactions from the easily accessible precursors 1,8- and 1,6-dibromopyrene, respectively. Both sets of compounds, equipped with eight peripheral aliphatic chains, self-assemble into a single hexagonal columnar mesophase, with one short-chain BBPn homolog also exhibiting another columnar mesophase at a lower temperature, with a rectangular symmetry; BBPn isomers also possess wider mesophase ranges and higher mesophases' stability than their DBPn homologs. These polycyclic aromatic hydrocarbons all show a strong tendency of face-on orientation on the substrate and could be controlled to edge-on alignment through mechanical shearing of interest for their implementation in photoelectronic devices. In addition, both series BBPn and DBPn display green-yellow luminescence, with high fluorescence quantum yields, around 30%. In particular, BBPn exhibit a blue shift phenomenon in both absorption and emission with respect to their DBPn isomers. DFT results were in good agreement with the optical properties and with the stability ranges of the mesophases by confirming the higher divergence from the flatness of DBPn compared with BBPn. Based on these interesting properties, these isomers could be potentially applied not only in the field of fluorescent dyes but also in the field of organic photoelectric semiconductor materials as electron transport materials. [ABSTRACT FROM AUTHOR]

Food lipid oxidation provides various volatile compounds involved in food flavor via the decomposition of lipid hydroperoxide (LOOH). This study predicted the pathways which can coherently explain LOOH decomposition focusing on hydroperoxy octadecadienoic acid (HpODE) isomers (9-EZ -HpODE, 9-EE-HpODE, 10-HpODE, 12-HpODE, 13-ZE-HpODE, and 13-EE-HpODE) which are the major LOOH contained in edible oils. Each standard was first prepared and thermally decomposed. Generated volatile and non-volatile compounds were analyzed by GC-MS and LC-MS/MS. The results showed that all HpODE decomposition was based on the factors such as favorable scission, radical delocalization, and cyclization. Interestingly, the formation of 8-HpODE and 14-HpODE were demonstrated during HpODE decomposition. The insights obtained in this study would explain the generation pathways of flavor involved in food quality. [ABSTRACT FROM AUTHOR]

A unified theoretical framework is presented for the isomeric excitation of the 229Th nucleus via electronic processes. These processes include nuclear excitation by electron transition (NEET), nuclear excitation by electron capture (NEEC), and nuclear excitation by inelastic electron scattering (NEIES). Detailed calculation results on the excitation rate and the excitation cross section are presented.