Critical approaches in the catalytic transformation of sugar isomerization and epimerization after Fischer-History,challenges,and prospects

The transformation of aldose to ketose or common sugars into rare saccharides,including rare ketoses and aldoses,is of great value and interest to the food industry and for saccharidic biomass utilization,medicine,and the synthesis of drugs.Nowadays,high-fructose corn syrup(HFCS)is industrially produced in more than 10 million tons annually using immobilized glucose isomerase.Some low-calorie saccharides such as tagatose and psicose,which are becoming popular sweeteners,have also been produced on a pilot scale in order to replace sucrose and HFCS.However,current catalysts and catalytic processes are still difficult to utilize in biomass conversion and also have strong substrate dependence in producing high-value,rare sugars.Considering the specific reaction properties of saccharides and catalysts,since the pioneering discovery by Fischer,various catalysts and catalytic systems have been discovered or developed in attempts to extend the reaction pathways,improve the reaction efficiency,and to potentially produce commercial products.In this review,we trace the history of sugar isomerization/epimerization reactions and summarize the important breakthroughs for each reaction as well as the difficulties that remain unresolved to date.

RuCl_3·3H_2O Mediated Olefin Isomerizations in Ionic Liquids: A Highly Recyclable System for Olefin Isomerizations

Herein lies a convenient and highly efficient method of olefin isomerization in the presence of RuCl3？3H2O in ionic liquid（IL）. More importantly, RuCl3？3H2O is a robust and recyclable catalyst. Nine cycles of RuCl3？3H2O as the catalyst were performed for the isomerization reactions of the selected substrate in IL and MeOH.

Study on Isomerous CAD Model Exchange Based on Feature

A model-exchange method based on feature between isomerous CAD systems is put forward in this paper.In this method,CAD model information is accessed at both feature and geometry levels and converted according to standard feature opera- tion.The feature information including feature tree,dimensions and constraints,which will be lost in traditional data conver- sion,as well as geometry are converted completely from source CAD system to destination one.So the transferred model can be edit- ed through feature operation,which cannot be implemented by general model-exchange interface.

Two Novel Isomers of HPS3 System

Two new isomers of HPS3 system, HP(S)S2 and HSSPS, are predicted by means of B3LYP method with 6-311++G(3df,3pd) basis set. The two isomers can isomerize into thermodynamically the most stable species HSPS2, which have been experimentally identified, with relatively higher reaction barriers. In view of their higher thermodynamical and kinetic stability and the experimental observation for HP(O)O2 and HOOPO in previous study, we can reasonably believe that the two species can be spectrosymmetrically characterized in future experiments.

A Theoretical Study on the Isomerization of HSOF System

Ab initio Hartree-Fock theory at the aug-cc-pvtz level is used to investigate the equilibrium structures and isomerization of HSOF system. All of the transition states have been calculated and confirmed by the intrinsic reaction coordinate (IRC). Four equilibrium structures, HSOF, HOSF, SO(H)F and OS(H)F, are predicted in this paper. Though OSF2 has been observed experimentally, the present calculated results suggest that the linear form isomer, HOSF, is more stable than OS(H)F by 35.2 kJ/mol. The linear form HSOF and the branched SO(H)F isomer are more unstable and the computed relative energies are 318.3 and 510.0 kJ/mol, respectively with respect to HOSF isomer corrected with zero point vibrational energy.

Ab Initio Studies on the [Os(PR_3)_4H(H_2)]^+ System

The [Os(PH3)4H(H2)]+ system was studied using the Gaussian 88 and the energy gradient technique at the restricted Hartree-Fock level under the effective core potential (ECP) approximation. The two different isomers of complex [Os(PH3)4H (H2)] (cis and trans) were optimized, and several orientations of the hydrogen molecule were considered for the cis isomer. When the hydride is placed in the cis position and oriented suitably, there is a strongly attractive effect between it and the molecular hydrogen.

ELECTRON TRANSFER AND PHOTOCHEMICAL VALENCE ISOMERIZATION IN ANTHRACENE AND NORBORNADIENE SYSTEMS

To harvest the sun light and to promote the amount of energy stored,a new binary compound which links a sensitizer(electron donor), anthracene,and substrate(electron acceptor),norbornadiene,in a non- conjugated manner without increase in molecular weight was synthesized.The inter-and intramolecular photosensitized isomerization and the mechanism were studied.

Systematics of Isomeric Cross Section Ratio for(n,t)Reaction at 14.6 MeV

On the basis of Hauser-Feshbach theory and some approximations,parametrized formulae of isomeric cross section ratio including two adjustableparameters for(n,t)reaction at 14.6MeV are derived.By fitting these formulae to theavailable measured data,parameters are obtained and the systematic behaviour of theisomeric cross section ratio are studied.The isomeric cross section ratio predicted by thepresent work is in good agreement with the limited measured data.

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.

Scheme for the excitation of thorium-229 nuclei based on electronic bridge excitation

Thorium-229 possesses the lowest first nuclear excited state,with an energy of approximately 8 eV.The extremely narrow linewidth of the first nuclear excited state,with an uncertainty of 53 THz,prevents direct laser excitation and realization of the nuclear clock.We present a proposal using the Coulomb crystal of a linear chain formed by229Th^(3+)ions,where the nuclei of229Th3+ions in the ion trap are excited by the electronic bridge(EB)process.The 7 P1∕2state of the thorium-229 nuclear ground state is chosen for EB excitation.Using the two-level optical Bloch equation under experimental conditions,we calculate that 2 out of 36 prepared thorium ions in the Coulomb crystal can be excited to the first nuclear excited state,and it takes approximately 2 h to scan over an uncertainty of 0.22 eV.Taking advantage of the transition enhancement of EB and the long stability of the Coulomb crystal,the energy uncertainty of the first excited state can be limited to the order of 1 GHz.

Measurement of^(134)Xe(n,2n)^(133m),gXe reaction cross sections in 14‑MeV region with detailed uncertainty quantification

A lead-shielded HPGe detector and offlineγ-ray spectra of the residual product were used to measure the cross section(CS)and ratios of isomeric CS(σm/σg)in^(134)Xe(n,2n)^(133m),gXe reactions at different energies(13.5 MeV,13.8 MeV,14.1 MeV,14.4 MeV,14.8 MeV)relative to the^(93)Nb(n,2n)^(92)mNb reaction CS.The target was high-purity natural Xe gas under high pressure.The T(d,n)4He reaction produces neutrons.TALYS code(version 1.95)for nuclear reactions was used for calculations,with default parameters and nuclear level density models.The uncertainties in the measured CS data were thoroughly analyzed using the covariance analysis method.The results were compared with theoretical values,evaluation data,and previous experimental findings.CS data of the 134Xe(n,2n)133mXe and 134Xe(n,2n)133gXe reactions and the corresponding isomeric CS ratios at 13.5 MeV,13.8 MeV,and 14.1 MeV neutron energies are reported for the first time.This research advances our knowledge of pre-equilibrium emission in the(n,2n)reaction channel by resolving inconsistencies in the Xe data.

Classifying Cardiac Anomalies in Right and Left Isomerism:Concordant and Discordant Patterns

Aims:Evidence is emerging that,in the setting of isomerism,the atrial and bronchial arrangement are not always concordant,nor are these patterns always harmonious with the arrangement of the abdominal organs.We aimed to evaluate the concordance between these features in a cohort of patients with cardiac malformations in the setting of known isomerism,seeking to determine whether it was feasible to assess complexity on this basis,in this regard taking note of the potential value of bronchial as opposed to appendage morphology.Methods and Results:We studied 78 patients known to have isomerism of the bronchuses,43 with right and 35 with left isomerism.Appendage anatomy could be determined in 49 cases(63%),all but one of these being concordant with bronchial anatomy.When assessing abdominal features,in only 59 cases(76%)was splenic morphology in keeping with the thoracic findings.As expected,right isomerism was associated with greater complexity of cardiac malformations,with an odds ratio of 6.53,with confidence intervals from 2.2–19.3(p<0.001).The odds were slightly decreased with thoraco-abdominal disharmony,when lesions shown to carry higher risk were then found in the setting of left isomerism.Conclusion:Harmony is excellent between bronchial and appendage isomerism,but less so with the arrangement of the abdominal organs.Right isomerism in our cohort,was indicative of a sixfold increase in intracardiac complexity.When discordance was found between the systems,however,the cardiac anomalies were less typical of the anticipated findings for right vs.left isomerism of the appendages.

Synthesis of MgO-doped ordered mesoporous carbons by Mg^(2+)-tannin coordination for efficient isomerization of glucose to fructose

In-situ MgO-doped ordered mesoporous carbon(OMC@MgO)was fabricated by formaldehyde-free self-assembly method,in which biomass-derived tannin was used as carbon precursor replacing fossil-based phenolics,Mg^(2+)as both cross-linker and precursor of catalytic sites.Up to~20 wt% MgO could be doped in the carbon skeleton with good dispersion retaining well-ordered mesoporous structures,while more MgO content(35 wt%)led to the failing in the formation of ordered mesoporous structure.The OMC@MgO possessed a high specific surface area(298.8 m^(2) g^(-1)),uniform pore size distribution(4.8 nm)and small crystallite size of MgO(1.73 nm)due to the confinement effect of ordered mesoporous structure.Using OMC@MgO as the heterogeneous catalyst,a maximum fructose yield of 32.4% with a selectivity up to 81.1%was achieved from glucose in water(90℃,60 min),which is much higher than that obtained using the MgO doped active carbon via conventional post-impregnation method(26.5%yield with 58.3% selectivity).Higher reaction temperature(>90℃)resulted in decrease of selectivity due to the formation of humins.The designed OMC@MgO displayed tolerant to high initial glucose concentrations(10 wt%)and could remain good recyclability without significant loss of activity for three cycles.

Drug adulteration analysis based on complexation with cyclodextrin and metal ions using ion mobility spectrometry

Drug adulteration and contamination are serious threats to human health therefore,their accurate monitoring is very important.Allopurinol(Alp)and theophylline(Thp)are commonly used drugs for the treatment of gout and bronchitis,while their isomers hypoxanthine(Hyt)and theobromine(Thm)have no effect and affect the efficacy of the drug.In this work,the drug isomers of Alp/Hyt and Thp/Thm are simply mixed withα-,β-,γ-cyclodextrin(CD)and metal ions and separated using trapped ion mobility spectrometry-mass spectrometry(TIMS-MS).TIMS-MS results showed that Alp/Hyt and Thp/Thm isomers could interact with CD and metal ions and form corresponding binary or ternary complexes to achieve their TIMS separation.Different metal ions and CDs showed different separation effect for the isomers,among which Alp and Hyt could be successfully distinguished from the complexes of[Alp/Hyt+γ-CD+Cu–H]^(+)with separation resolution(RP–P)of 1.51;whereas Thp and Thm could be baseline separated by[Thp/Thm+γ-CD+Ca–H]^(+)with RP–P of 1.96.Besides,chemical calculations revealed that the complexes were in the inclusion forms,and microscopic interactions were somewhat different,making their mobility separation.Moreover,relative and absolute quantification was investigated with an internal standard to determine the precise isomers content,and good linearity(R^(2)>0.99)was obtained.Finally,the method was applied for the adulteration detection where different drugs and urine were analyzed.In addition,due to the advantages of fast speed,simple operation,high sensitivity,and no chromatographic separation required,the proposed method provides an effective strategy for the drug adulteration detection of isomers.

A novel synthesis of highly active and highly stable non-noble-nickel-modified persulfated Al_(2)O_(3)@ZrO_(2) core-shell catalysts for n-pentane isomerization

The non-noble metal modified sulfated zirconia was found easy to deactivate.Herein,highly active and highly stable non-noble core-shell Ni-S_(2)O_(8)^(2−)/Al_(2)O_(3)@ZrO_(2) catalysts(Ni-SA@Z-x,x=Al content in wt%)have been successfully prepared and investigated for n-pentane isomerization.The results showed that the core-shell Ni-SA@Z-30 provided a sustained high isopentane yield(63.1%)with little or no deactivation within 5000 min at a mild reaction pressure of 2.0 MPa,which can be attributed to the following factors:(i)carbon deposition was greatly suppressed by the large pore size and huge pore volume;(ii)the loss of sulfur entities was suppressed because the small and highly dispersed tetragonal ZrO_(2) particles can bond with the S species strongly;(iii)strong Brønsted acidity can be maintained well after the isomerization.The pore structures and acid nature of the core-shell Ni-SA@Z-x are entirely different from those of the normal structure Ni-S_(2)O_(8)^(2−)/ZrO_(2)-Al_(2)O_(3),even though the Al content and the compositions of the individual components are the same.The Al_(2)O_(3)cores endow the catalysts with high internal surface area and high mechanical strength.Meanwhile,the ZrO_(2) shell,which consists of more and smaller tetragonal ZrO_(2) particles because of the large surface area of the Al_(2)O_(3)core,promotes the formation of more stable sulfur species and stronger binding sites.

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.

Quantum Dynamics Calculations on Isotope Effects of Hydrogen Transfer Isomerization in Formic Acid Dimer

We present a quantum dynamics study on the isotope effects of hydro-gen transfer isomerization in the formic acid dimer,and this is achieved by multidimensional dy-namics calculations with an efficient quantum mechanical theoretical scheme developed by our group,on a full-dimensional neural network ab initio potential energy surface.The ground-state and fundamental tun-neling splittings for four deuterium isotopologues of formic acid dimer are considered,and the calculated results are in very good general agreement with the avail-able experimental measurements.Strong isotope effects are revealed,the mode-specific funda-mental excitation effects on the tunneling rate are evidently influenced by the deuterium sub-stitution of H atom with the substitution on the OH bond being more effective than on the CH bond.Our studies are helpful for acquiring a better understanding of isotope effects in the double-hydrogen transfer processes.

Seed-solution-induced Synthesis of FER Zeolite and Its Catalytic Application in the Skeletal Isomerization of n-Butene

A series of Ferrierite(FER)zeolites were prepared via hydrothermal synthesis in the absence of organic templates with the aid of sodium-type FER zeolite(NaFER)or NaFER suspensions(NaFERsus)acquired by NaOH solution treatment as seeds.The differences in the structures and acid sites of the obtained FER zeolite catalysts arising from the choice of seed were investigated,and the catalytic performances of the obtained FER zeolites were evaluated in the skeletal isomerization of n-butene.The results indicate that the samples synthesized using NaFERsus feature more Br?nsted acid sites(BAS)in the 10-membered-ring(10-MR)at the expense of strong acid and Lewis acid sites(LAS),compared with samples derived from NaFER.Therefore,the FER samples synthesized using NaFERsus outperformed the NaFER counterparts as the BAS in 10-MR and LAS were the main active sites,while BAS in 8-MR and LAS were responsible for side reactions,such as polymerization,cracking,and carbon deposition in n-butene isomerization.The optimized FER catalyst was continuously used for 720 h at 350℃ at 0.1 MPa under an n-butene space velocity of 2.0 h^(-1),during which the n-butene conversion remained at>40%,and the isobutylene yield was>37.5%.

Irvingia Fat Ageing: Study of Chemical Characteristics Related to MIR Spectroscopy

The Irvingia gabonensis kernels, which have been extensively studied for their numerous virtues, including the ability to act against the accumulation of fats in the body[1], contain an oil. The aging of this oil under two different conditions of conservation was the subject of our work. One of the results was an increase in the content of long-chain carbonaceous fatty acids during aging for 11 months of storage at low temperature (6℃) and at 30℃. This behavior does not find a concordant explanation by the comparative analysis of the chemical indices. Hence, there is the need to use the Medium Infra-Red spectroscopy (MIR) which allowed to clarify the information of the saponification index, to justify the weakness of the formation of peroxides in the case of the conservation at 30℃ and to confirm the information given by the peroxide index. It also allowed to understand the formation of the long carbon chains by the “cis-trans” isomerization and the homolytic cuts which intervene within the matrix of the fat by the analysis of the number of -CH2 and -CH3 groups in the two conditions of conservation. This study reveals that the rapid solidification of Irvingia gabonensis oil at room temperature[2] is an advantage for its preservation at room temperature but a great weakness when the fat is stored at low temperature.