Structural Isomers:Small Change with Big Difference in Anion Storage

Organic electrode materials are promising for batteries.However,the reported organic electrodes are often facing the challenges of low specific capacity,low voltage,poor rate capability and vague charge storage mechanisms,etc.Isomers are good platform to investigate the charge storage mechanisms and enhance the performance of batteries,which,however,have not been focused in batteries.Herein,two isomers are reported for batteries.As a result,the isomer tetrathiafulvalene(TTF)could store two monovalent anions reversibly,deriving an average discharge voltage of 1.05 V and a specific capacity of 220 mAh g−1 at a current density of 2 C.On the other hand,the other isomer tetrathianaphthalene could only reversibly store one monovalent anion and upon further oxidation,it would undergo an irreversible solid-state molecular rearrangement to TTF.The molecular rearrangement was confirmed by electrochemical performances,X-ray diffraction patterns,nuclear magnetic resonance spectra,and 1H detected heteronuclear multiple bond correlation spectra.These results suggested the small structural change could lead to a big difference in anion storage,and we hope this work will stimulate more attention to the structural design for boosting the performance of organic batteries.

Photonuclear production of nuclear isomers using bremsstrahlung induced by laser-wakefield electrons

In this study,we theoretically investigate the feasibility of using laser-wakefield accelerated(LWFA)electrons for the photonuclear measurement of nuclear isomers according to the characteristics of the electrons obtained from LWFA experiments conducted at the Compact Laser-Plasma Accelerator(CLAPA)laboratory.The experiments at the CLAPA show that a stable electron beam with an energy of 78-135 MeV and a charge of 300-600 pC can be obtained.The bremsstrahlung spectra were simulated using Geant4,which suggests that a bremsstrahlung source with a peak intensity of 10^(19) photons/s can be generated.Theoretical calculations of isomer production cross sections from the photonuclear reactions on six target nuclei,^(197)Au,^(180)Hf,^(159)Tb,^(115)In,^(103)Rh,and ^(90)Zr,were performed and compared with the available experimental data in EXFOR,which suggest that further experiments are required for a series of photonuclear reaction channels.Flux-averaged cross sections and isomer ratios(IR)resulting from such bremsstrahlung sources are theoretically deduced.The results suggest that IR measurements can be used to constrain nuclear components,such asγstrength function and optical model potential.In addition,the detection of the decay characteristics was evaluated with Geant4 simulations.The use of the LWFA electron beam and its bremsstrahlung for photonuclear studies involving nuclear isomers is anticipated.

Fragmentation stability and retention time-shift obtained by LC-MS/MS to distinguish sialylated N-glycan linkage isomers in therapeutic glycoproteins

Sialylated N-glycan isomers withα2-3 orα2-6 linkage(s)have distinctive roles in glycoproteins,but are difficult to distinguish.Wild-type(WT)and glycoengineered(mutant)therapeutic glycoproteins,cytotoxic T lymphocyte-associated antigen-4-immunoglobulin(CTLA4-Ig),were produced in Chinese hamster ovary cell lines;however,their linkage isomers have not been reported.In this study,N-glycans of CTLA4-Igs were released,labeled with procainamide,and analyzed by liquid chromatography-tandem mass spectrometry(MS/MS)to identify and quantify sialylated N-glycan linkage isomers.The linkage isomers were distinguished by comparison of 1)intensity of the N-acetylglucosamine ion to the sialic acid ion(Ln/Nn)using different fragmentation stability in MS/MS spectra and 2)retention time-shift for a selective m/z value in the extracted ion chromatogram.Each isomer was distinctively identified,and each quantity(>0.1%)was obtained relative to the total N-glycans(100%)for all observed ionization states.Twenty sialylated N-glycan isomers with onlyα2-3 linkage(s)in WT were identified,and each isomer's sum of quantities was 50.4%.Furthermore,39 sialylated N-glycan isomers(58.8%)in mono-(3 N-glycans;0.9%),bi-(18;48.3%),tri-(14;8.9%),and tetra-(4;0.7%)antennary structures of mutant were obtained,which comprised mono-(15 N-glycans;25.4%),di-(15;28.4%),tri-(8;4.8%),and tetra-(1;0.2%)sialylation,respectively,with onlyα2-3(10 N-glycans;4.8%),bothα2-3 andα2-6(14;18.4%),and onlyα2-6(15;35.6%)linkage(s).These results are consistent with those forα2-3 neuraminidase-treated N-glycans.This study generated a novel plot of Ln/Nn versus retention time to distinguish sialylated N-glycan linkage isomers in glycoprotein.

Research on the Relationship between Three Isomers of Microcystins and Environmental Factors

[Objective] The relationship between three isomers of microcystins and environmental factors were studied in the fields.[Method] Three isomers of microcystins （MC-LR,RR and YR） from water of five sampling spots in a northern reservoir were observed for one year with High Performance Liquid Chromatography analytical method in order to study the relationship between three isomers and environmental factors.[Result] The three isomers of microcystins showed positive correlation with chlorophyll a;LR and YR isomers all had significant linear positive correlations with the water temperature,but the RR isomer showed no significant correlation with the water temperature;LR and YR isomers had relatively significantly correlativities with the contents of total nitrogen,nitrate nitrogen and organic nitrogen,while the RR isomer only showed a significant negative correlation with the content of nitrate nitrogen;LR and RR isomers both showed significant positive correlations with the contents of total phosphorus and organic phosphorus,while the phosphorus hardly affected the YR isomer and showed no evident correlation.[Conclusion] The relationship between three isomers of microcystins and environmental factors such as chlorophyll a,water temperature,nitrogen,phosphorus were studied and investigated the reasons,which might offered a reference for controlling the growth of blue algae in water and toxin synthesis.

Differentiation of Positional Isomers of Propyl Alcohols Using Filament-Induced Fluorescence

We experimentally demonstrate the recognition of positional isomers of propyl alcohol vapor through nonlinear fluorescence induced by high-intensity femtosecond laser filaments in air. By measuring characteristic fluorescence of n-propyl and isopropyl alcohol vapors produced by femtosecond filament excitation, it is found that they show identical spectra, that is, those from molecular bands of CH, C2, Nit, OH and CN, while the relative intensities are different. By comparing the ratios of the CH and C2 signals, the two propyl alcohol isomers are differentiated. The different signal intensities are ascribed to different ionization potentials of the two isomer molecules, leading to different production efficiencies of fluorescing fragments.

Ohmefentanyl stereoisomers induce changes of CREB phosphorylation in hippocampus of mice in conditioned place preference paradigm

The present study was designed to determine the changes of phosphorylation of cAMP- response ele-ment binding protein (CREB) in hippocampus induced by ohmefentanyl stereoisomers (F9202 and F9204)in conditioned place preference (CPP) paradigm. The results showed that mice receiving F9202 and F9204displayed obvious CPP. They could all significantly stimulate CREB phosphorylation and maintained for along time without affecting total CREB protein levels. The effect of F9204 was similar to morphine whicheffect was more potent and longer than F9202. We also examined the effects of ketamine, a noncompetitiveN-mthyl-D-aspartate receptor (NR) antagonist, on morphine-, F9202- and F9204- induced CPP and phos-phorylation of CREB in hippocampus. Ketamine could suppress not only the place preference but also thephosphorylation of CREB produced by morphine, F9202 and F9204. These findings suggest that alterationsin the phosphorylation of CREB be relevant to opiates signaling and the development of opiates dependence.NR antagonists may interfere with opiates dependence and may have potential therapeutic implications.

Global characterization of modifications to the charge isomers of IgG antibody

Posttranslational modifications of antibody products affect their stability,charge distribution,and drug activity and are thus a critical quality attribute.The comprehensive mapping of antibody modifications and different charge isomers(CIs)is of utmost importance,but is challenging.We intended to quantitatively characterize the posttranslational modification status of CIs of antibody drugs and explore the impact of posttranslational modifications on charge heterogeneity.The CIs of antibodies were fractionated by strong cation exchange chromatography and verified by capillary isoelectric focusing-whole column imaging detection,followed by stepwise structural characterization at three levels.First,the differences between CIs were explored at the intact protein level using a top-down mass spectrometry approach;this showed differences in glycoforms and deamidation status.Second,at the peptide level,common modifications of oxidation,deamidation,and glycosylation were identified.Peptide mapping showed nonuniform deamidation and glycoform distribution among CIs.In total,10 N-glycoforms were detected by peptide mapping.Finally,an in-depth analysis of glycan variants of CIs was performed through the detection of enriched glycopeptides.Qualitative and quantitative analyses demonstrated the dynamics of 24 N-glycoforms.The results revealed that sialic acid modification is a critical factor accounting for charge heterogeneity,which is otherwise missed in peptide mapping and intact molecular weight analyses.This study demonstrated the importance of the comprehensive analyses of antibody CIs and provides a reference method for the quality control of biopharmaceutical analysis.

Aromatic Character of All Possible C_(36)H_2 Isomers

The stability of C36H2 isomers and selection rules for choosing position in addition reactions based on symmetrical C36（D6h and D2d） fullerene have been studied by means of Aihara＇s topological resonance energy （TRE） and bond resonance energy （BRE） methods. The relation between the addition pattern and BREs is established, showing high antiaromatic bonds are preferred for addition. These results show that TRE and BRE methods can be used to predict and interpret addition sites for these systems.

Separation and identification of cis and trans isomers of 2-butene-1,4-diol and lafutidine by HPLC and LC-MS

The cis and trans isomers separation of 2-butene-1,4-diol and lafutidine were studied by HPLC on two kinds of chiral columns: (S,S)-Whelk-O 1 and ChiraSpher. The isomers of 2-butene-1,4-diol can be separated on both chiral columns while the isomers of lafutidine can only be resolved on ChiraSpher column. The influence of different type and amount of mobile phase modifier on the isomers separation was extensively studied. The resolution of cis and trans isomers of 2-butene-1,4-diol was 2.61on (S,S)-Whelk-O 1 column with hexane-ethanol (97:3, v/v) as the mobile phase. The resolution of lafutidine was 1.89 on ChiraSpher column with hexane-ethanol-THF-diethylamine (92:3:5:0.1, v/v/v/v) as the mobile phase. LC-MS methods were developed to identify the isomer peaks.

Theoretical Studies on Stabilities of C_(26)BN Isomers

The possible stable structures of substituted fullerene C26BN formed on the initial C28 cage with Td symmetry have been systematically studied on UHF/3-21g level with constrained symmetry(Cs or C1), the charge and multiplicity of all the isomers are zero and five, respectively. The geometry optimization and the vibrational frequencies analysis were performed on the same level with constrained symmetry(Cs or C1). The results show that the most stable isomer of C26BN is formed by boron and nitrogen atoms doping at 5,2-sites.

DFT Study on Two C_4N_(12)O_4 Isomers with Pagodane- and Isopagodane-like Structures

Geometries, energies, and vibrational frequencies for two C4N12O4 isomers with pagodane- and isopagodane-like structures have been calculated at the B3LYP/6-31G＊ level.Isomers 1 and 2 are of D2h and D2d symmetry, respectively. Heats of formation for the two C4N12O4 isomers have been estimated in this paper, indicating they would be reasonable candidates for high energy density materials.

EFFECT OF NITRATE AND PHOSPHATE ON ACCUMULATION OF β-CAROTENE ISOMERS IN DUNALIELLA SALINA

DunaIiella salina, a halotolerent unicellular green alga, can accurmulate a Iarge amount of β-caroteneunder environmental conditions. The isorners of β-carotene extIacted from D. salina culturedin medium with different nitrate and phosphate concentrations were analysed by HPLC with Alox-Talumins column. At least six isomers were found in different proportions depending on the culture me-dia’s nitrate and/or phosphate concentrations. Nitrate and/or phosphae defidency was conducive tothe accumulation of totaI cis isomers but not of al1 trans isomer. lt is sUggeSted that 1 mmol/L KNO3and 0.1 mmol/L KH2, PO4 are favourable for accumulation of total cis β-carotene.

A density functional study on some cyclic N_(10) isomers

Polynitrogen compounds, comprising only nitrogen atoms, are rare. They are considered as promising candidates of clean(green) high energy density materials because of their high energy content and their sole decomposition product is N_2. Extending the previous work which was on cyclic N_8 isomers, in this study some cyclic N_(10) isomers having 1-4 cycles are considered within the limitations of density functional theory at the levels of B3LYP/6-311++G(d,p) and B3LYP/cc-PVTZ. Some of the structures,including the monocyclic one, decompose by eliminating certain number of N_2 units while some remain intact. All the stable isomers(1-3, 6-8) investigated presently are highly endothermic that they are candidates for clean high energy materials. Certain quantum chemical properties, IR and UV-VIS spectra as well as the specific impulse values for the stable structures are reported.

New tricks for an old dog: Visible light-driven hydrogen production from water catalyzed by fac-and mer-geometrical isomers of tris(thiosemicarbazide) cobalt(Ⅲ)

Increasing interest has been paid to the development of earth‐abundant metal complexes as promising surrogates of platinum for the electrocatalytically and photocatalytically driven hydrogen evolution reaction.In this work,we report on molecular H2‐evolving catalysts based on two octahedral complexes of cobalt thiosemicarbazide,fac‐[Co(Htsc)3]Cl3·3H2O(C1,Htsc=thiosemicarbazide)and mer‐[Co(Htsc)3]Cl3·4H2O(C2),which have facial(fac)and meridional(mer)geometry,respectively.Electrochemical studies confirmed that both C1and C2are active electrocatalysts in MeOH solution using acetic acid as the proton source,with the same overpotential of^640mV and TOF of^210s–1.The complex C1also exhibits electrocatalytic activity for hydrogen evolution reaction in aqueous media free of organic solvent with a moderate overpotential(560mV).Visible light‐driven hydrogen evolution experiments were carried out in combination with fluorescein as photosensitizer and triethylamine as sacrificial reductant in homogeneous environments.Our studies showed that both C1and C2can be used as efficient proton‐reduction catalysts in purely aqueous solution and have the same photocatalytic activities.A TOF of125h–1with a TON of900for photocatalytic H2generation using C1and C2in water were achieved for the noble‐metal‐free homogeneous system.It should be noted that this is the first reported study investigating the effect on the catalytic hydrogen production performance of using fac‐and mer‐isomers of molecular catalysts.

MULTIDIMENSIONAL GAS CHROMATOGRAPHY FOR THE SEPARATION OF TCDD ISOMERS

A multidimensional gas chromatographic technique with heartcutting was used for the determination of complex isomeric mixtures of tetra- chlorodibenzo-p-dioxins(TCDDs)which could not be completely separated on a single capillary column.When using so-called heartcutting technique ,only the interested single peak or section of the fraction eluting from the first column was transferred onto the second column with different stationary phase.Flame ionization detection was used as the monitor detector and electron capture detection as the main detector.This arrangement offers complete separation and avoids interference of the possible remained chlorinated solvents.The separation power of multi- dimensional GC was demonstrated by the determination of TCDD isomers.

Gas chromatographic separation and determination of chloroanthracene isomers on fly ash

An efficient, reproducible and rapid fused silica capillary column gas chromatographic method, in splitless mode, for analysing of the three chloroanthracene isomers is described. The method affords efficient separation and good linearity for each isomer in the range of 0.2 -200 μg/ml. The method can also be used in separation and determination of another thirty three aromatic and their halosubstituted compounds. This paper also presents the applications of the method in analysing of complex products mixture from reaction of the selected aromatic compounds with hydrogen chloride on fly ash surface from municipal incinerator.

A Good GC Stationary Phase for Separation of Xylene Isomers

An excellent separation of xylene isomers is reported using 2, 6-O-di-pentyl-3-O-acetyl-beta-CD as capillary stationary phase. The optimum conditions for the separation are also discussed.

The Crystal Structure of Biphenyltetracarboxylic Dianhydride Isomers

Biphenyltetracarboxylic dianhydride (2,2',3,3' BPDA), C 16 H 6O 6, M r =294.21, monoclinic, P2 1/c, a=11.694(2), b=8.111(2), c=13 494(3) , β=103.47(3)°, V=1244.7(4) 3, Z=4, D c =1.570 g/cm 3 , F (000)=450, Mo Kα radiation( λ =0.71073), μ (Mo Kα )=0.092 mm -1 , R =0.0329 for 2180 observed reflections 〔 I>2σ(I) 〕. 3,3',4,4' Biphenyltetracarboxylic dianhydride (3,3',4,4' BPDA), C 16 H 6O 6, M r =294.21, monoclinic, P2 1/n, a=6.8720(14), b=5.1870(10), c=17.288(4), β=94.96(3)°, V= 613.9(2) 3, Z=2, D c =1 592 gcm -3 , F(000)=300 , μ (Mo Kα )=0.125mm -1 , R =0.0331 for 1079 observed reflections〔 I>2σ(I) 〕. The dianhydride isomers have different symmetry caused by alternating two anhydride group positions and the dihedral angle between the two phenyl rings are 62.9°for 2,2',3,3', BPDA and 0°for 3,3',4,4' BPDA respectively.

STUDIES ON CHIRAL THIOPHOSPHORIC ACIDS AND THEIR DERIVATIVES 11.——THE RESOLUTION OF O-METHYL O-PHENYL THIOPHOSPHORIC ACID AND ABSOLUTE CONFIGURATIONS OF ITS OPTICAL ISOMERS

Racemic O-methyl O-pheayl thiophosphoric acid 1 has been successfully resolved through its quinine and brucine salts in methanol solution by fractional crystallization. The absolute configurations of the optically active 1 have been established as (+)-R-1 and (-)-S-1 by chemical correlation.

An Excellent Gas Chromatographic Stationary Phase for Separation of Phenol and Cresol Isomers--Heptakis(2,6-di-O-pentyl-3-O-allyl)-β-Cyclodextrin

Heptakis(2.6-di-O-pentyl-3-O-ally)-β-cyclodextrin as an excellent gas chromatographic stationary phase separating phenol and cresol isomers is described.