The synthesis of ferrierite(FER)zeolite using piperidine as an organic structure‐directing agent was investigated.X‐ray diffraction,X‐ray fluorescence,N2‐adsorption,and scanning electron microscopy were used to ch...The synthesis of ferrierite(FER)zeolite using piperidine as an organic structure‐directing agent was investigated.X‐ray diffraction,X‐ray fluorescence,N2‐adsorption,and scanning electron microscopy were used to characterize the crystal phases,textural properties,and particle morphologies of the zeolite samples.The crystallization behavior of the FER zeolite was found to be directly related to crystallization temperature.At150?C,pure FER phase was observed throughout crystallization.At160–170?C,MWW phase appeared first and gradually transformed into FER phase over time,indicating that the FER phase was thermodynamically favored.In the piperidine‐Na2O‐H2O synthetic system,alkalinity proved to be the crucial factor determining the size and textural properties of FER zeolite.Furthermore,the obtained FER samples exhibited good catalytic performance in the skeletal isomerization of1‐butene.展开更多
A novel melting-assisted solvent-free route using solid oxalic acid was proposed for the post-treatment of SAPO-11 zeolite,followed by loading with 0.5 wt%Pt by the incipient wetness impregnation method.Subsequently,t...A novel melting-assisted solvent-free route using solid oxalic acid was proposed for the post-treatment of SAPO-11 zeolite,followed by loading with 0.5 wt%Pt by the incipient wetness impregnation method.Subsequently,the performance of the obtained bifunctional catalysts toward the hydroisomerization of n-dodecane was examined.The prepared samples were characterized by XRD,SEM,BET,XRF,Py-IR,and solid-state NMR.From the results,it was found that the high crystallinity and uniform morphology were retained after the post-treatment and that more(002)crystal faces were exposed,which was beneficial since more acid sites were provided.More importantly,the total Bronsted acid sites and the ratio(Ra)of the micropore area to the total surface area were optimized by this method.Thus,the catalytic performance was enhanced significantly,and the prepared Pt-SAPO-11-10%catalyst had the highest i-dodecane yield of 80.1%compared to 55.3%of Pt-SAPO-11.Expectedly,this facile and cost-effective method is promising for the hydroisomerization of normal paraffin in the production of lubricant base oils.展开更多
Energy raolved mass spectra (ERMS) of 2, 3-DNT and 3, 5-DNT isomers was mported. The fragmentation of this pair of DNTisomers was studied by ERMS in electron impact (EI),and their breakdown curves were discussed , T...Energy raolved mass spectra (ERMS) of 2, 3-DNT and 3, 5-DNT isomers was mported. The fragmentation of this pair of DNTisomers was studied by ERMS in electron impact (EI),and their breakdown curves were discussed , These nitraromaic isomers can be characterized according to the differences between their ERMS in MS/MS展开更多
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 c...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.展开更多
Metal-loaded zeolite catalysts were synthesized and examined in the hydroisomerization of n-decane.Specifically,zeolite Y was impregnated with 0.1 wt%Pd and varying amounts of Ni（0.1-0.5 wt%].The crystallinity of the...Metal-loaded zeolite catalysts were synthesized and examined in the hydroisomerization of n-decane.Specifically,zeolite Y was impregnated with 0.1 wt%Pd and varying amounts of Ni（0.1-0.5 wt%].The crystallinity of the metal-loaded catalysts was characterized by X-ray diffraction,and the average metal particle size was determined by transmission electron microscopy.The states of Pd and Ni were identified by X-ray photoelectron spectroscopy.Ammonia temperature-programmed desorption analysis revealed the occurrence of ion-exchange of some of the catalyst acid sites with Ni-（2＋）.The reducibility of the HY zeolite-supported Pd,Ni,and Pd-Ni catalysts was studied by temperature-programmed reduction.The hydroisomerization of n-decane over the prepared catalyst was conducted at 200-450℃ under 1 atm.Ni addition of up to 0.3 wt%over 0.1 wt%Pd/HY enhanced the n-decane conversion and isomerization product selectivity.The improved selectivity of the mono- and dibranched isomers suggested the occurrence of a protonated cyclopropane intermediate mechanism.However,further Ni addition above 0.3 wt%considerably reduced the activity and isomerization selectivity.The bimetallic catalysts were more selective toward the formation of dibranched isomers,i.e.,those containing a higher octane number.展开更多
To compare genetic markers for population genetics analysis, allozyme electrophoresis and random amplified polymorphic DNA （RAPD） were used to detect the genetic structure of scallop Chlamysfarreri population. Thirt...To compare genetic markers for population genetics analysis, allozyme electrophoresis and random amplified polymorphic DNA （RAPD） were used to detect the genetic structure of scallop Chlamysfarreri population. Thirteen enzymes （MDH, ME, IDH, GPI, PGM, PEP-LG, PEP-pp, ACP, AK, PK, AAT, SOD, EST） in three butter systems （TC, pH6.9; TMME, pH 7.4; and EBT, pHS.9） were selected and 22 loci were used for the analysis, among them 7 loci （Gpi, Pgm, Pep.m-l, Pep.pp. Aat-2, Est-2, Est-3） were polymorphic which attributed 31.82% to the total. The average of heterozygosity was 0.113 and most of the studied loci showed heterozygote deficiencies. The same specimens were investigated using 10 arbitrarily selected primers （10-base）. Twenty two of 54 RAPD fragments were polymorphic with average heterozygosity of 0.194. The result indicated that the two types of markers reflected a consistent trend in the parameter values of genetic diversity of the population, but RAPD revealed more information of genetic variation than allozyme electrophoresis.展开更多
The aromaticity of all possible substituted fullerene isomers of C18N2, C18B2, C18BN, and their molecular ions which originate from the C20 （Ih） cage were studied by the topological resonance energy （TRE） and the ...The aromaticity of all possible substituted fullerene isomers of C18N2, C18B2, C18BN, and their molecular ions which originate from the C20 （Ih） cage were studied by the topological resonance energy （TRE） and the percentage topological resonance energy methods. The relationship between the aromaticity of C18BxNy isomers and the sites where the heteroatoms dope at the C20 （Ih） cage is discussed. Calculation results show that at the neutral and cationic states all the isomers are predicted to be antiaromatic with negative TREs, but their polyvalent anions are predicted to be aromatic with positive TREs. The most stable isomer is formed by heteroatom doping at the 1,11-sites in C18N2. C18B2, and C18BN. Heterofullerenes are more aromatic than C20. The stability order in the neutral states is C18N2〉C18BN〉C18B2〉C20. The stability order in closed-shell is C18B2^8- 〉C20^6- 〉C18BN^6- 〉C18N2^4-. This predicts theoretically that their polyvalent anions have high aromaticity.展开更多
The complex model of Thermus thermophilus xylose isomerase （TtXI） with D-xylose was constructed, and molecular dynamics （MD） simulations were carried out at 300 and 360 K for 10 ns by NAMD2.5. The radius of gyrati...The complex model of Thermus thermophilus xylose isomerase （TtXI） with D-xylose was constructed, and molecular dynamics （MD） simulations were carried out at 300 and 360 K for 10 ns by NAMD2.5. The radius of gyration （Rg）, subunit interactions, and residue flexibility were analyzed. The results show that residues 60-69, 142-148, 169-172, and 332-340 have high flexibility at 300 and 360 K. Residues with higher flexibility at 360 K than that at 300 K can mainly be divided into two groups： one locates in the helix-loophelix region consisting of residues 55-80 in catalytic domain; the other at subunit interfaces. The Rg of catalytic domain at 360 K shows 0.16 A higher than that at 300 K, but Rg of small C-terminal domain has no obvious difference. The results indicate that enhanced Rg of catalytic domain may lead to the intense motion of the active site of TtXI and promote the D-xylose isomization reaction. Eight hydrogen bonds and five ion pairs are reduced at subunit interfaces at 360 K compared with 300 K, that may be the main reason for the decrease in rigidity and increase in activity at high temperature of TtXI. This result also help to explain the cold-adaption phenomenon of TtXI E372G mutant reported previously. Our results reveal the relationship between temperature and structure flexibility of TtXI, and play an important role in understanding the thermostability of thermophile protein with multiple subunits.展开更多
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 thi...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.展开更多
The rational design of photochemical molecular device(PMD)and its hybrid system has great potential in improving the activity of photocatalytic hydrogen production.A series of Pd6L3 type metal-organic cages,denoted as...The rational design of photochemical molecular device(PMD)and its hybrid system has great potential in improving the activity of photocatalytic hydrogen production.A series of Pd6L3 type metal-organic cages,denoted as MOC-Py-M(M=H,Cu,and Zn),are designed for PMDs by combining metalloporphyrin-based ligands with catalytically active Pd^(2+)centers.These metal-organic cages(MOCs)are first successfully hybridized with graphitic carbon nitride(g-C_(3)N_(4))to form direct Z-scheme heterogeneous MOC-Py-M/g-C_(3)N_(4)(M=H,Cu,and Zn)photocatalysts via π-πinteractions.Benefiting from its better light absorption ability,the MOC-Py-Zn/g-C_(3)N_(4) catalyst exhibits high H_(2) production activity under visible light(10348μmol g^(-1) h^(-1)),far superior to MOC-Py-H/g-C_(3)N_(4) and MOC-Py-Cu/g-C_(3)N_(4).Moreover,the MOC-Py-Zn/g-C_(3)N_(4) system obtains an enhanced turn over number(TON)value of 32616 within 100 h,outperforming the homogenous MOC-Py-Zn(TON of 507 within 100 h),which is one of the highest photochemical hybrid systems based on MOC for visible-light-driven hydrogen generation.This confirms the direct Z-scheme heterostructure can promote effective charge transfer,expand the visible light absorption region,and protect the cages from decomposition in MOC-Py-Zn/g-C_(3)N_(4).This work presents a creative example that direct Z-scheme PMD-based systems for effective and persistent hydrogen generation from water under visible light are obtained by heterogenization approach using homogeneous porphyrin-based MOCs and g-C_(3)N_(4) semiconductors.展开更多
Investigations show that in monomer water heterogeneous systems polymerization, located in the interface, can disperse the system. Following polymerization in the density gradient field it is shown that in such system...Investigations show that in monomer water heterogeneous systems polymerization, located in the interface, can disperse the system. Following polymerization in the density gradient field it is shown that in such systems latex particles are nucleated from monomer microdroplets, containing a certain amount of polymer molecules. It could be considered that, independently of the nature of the monomer itself, polymerization in monomer water statistic heterogeneous systems modulate emulsion polymerization process.展开更多
Exo-tetrahydrodicyclopentadiene （exo-TCD） is an important high-energy fuel. Silicotungstic acid （SiW） immobilized on H-type β zeolite （Hβ） at room temperature were used to prepare the Hβ zeolite catalysts wit...Exo-tetrahydrodicyclopentadiene （exo-TCD） is an important high-energy fuel. Silicotungstic acid （SiW） immobilized on H-type β zeolite （Hβ） at room temperature were used to prepare the Hβ zeolite catalysts with different SiW contents. Catalytic performances of the catalysts were investigated during the preparation of exo-TCD via isomerization of endo-tetrahydrodicyclopentadiene （endo-TCD）. The properties of catalysts were characterized by XRD, temperature pro- grammed desorption of ammonia （NHa-TPD）, FT-IR, and N2-adsorption techniques. SiW was highly dispersed on the surface of Hβ zeolite, and the 10% SiW/Hβ zeolite catalyst had the highest amount of weak acidity among all SiW/Hβ zeolite catalysts. The influence of different factors on isomerization reaction was investigated. At a reaction temperature of 240 ℃, a n（cyclohexane） / n（endo-TCD） ratio of 10, a m（catalyst）/m（endo-TCD） ratio of 0.3, an initial pressure of 1.0 MPa, and a reaction time of 1.5 h in the presence of 10% SiW/Hβ catalyst calcined at 400 ℃, the conversion of endo-TCD reached up to 92.0%, with the yield of exo-TCD equating to 51.0%.展开更多
The performance of MCM-22 zeolite for catalytic isomerization of 1-hexene has been studied. At a n(H2)/n(1-hexene) ratio of 8, the influence of steam treatment temperature, reaction temperature and reaction pressure o...The performance of MCM-22 zeolite for catalytic isomerization of 1-hexene has been studied. At a n(H2)/n(1-hexene) ratio of 8, the influence of steam treatment temperature, reaction temperature and reaction pressure on the performance of MCM-22 zeolite for catalytic skeletal isomerization of 1-hexene was examined. The experimental results showed that at a steam treatment temperature of 500℃, a reaction temperature of 270℃, a space velocity of 1.0 h-1 and a reaction pressure of 0.2 MPa, the MCM-22 zeolite exhibited excellent performance for catalytic skeletal isomerization of 1-hexene with the i-hexene yield reaching 66.15%. Compared with other commonly used molecular sieve catalysts, the MCM-22 zeolite catalyst exhibited better catalytic performance for skeletal isomerization of 1-hexene.展开更多
A study of the influence of magnetic field on the tautomerism, the authors proposed a new method for predicting possible new intra- and intermolecular rearrangements due to tautomerism. The authors have proposed a gen...A study of the influence of magnetic field on the tautomerism, the authors proposed a new method for predicting possible new intra- and intermolecular rearrangements due to tautomerism. The authors have proposed a general mechanism of possible rearrangements and tautomerism.展开更多
The manuscript deals with the possibility of application of collective behavior of quantum particles to realize the quantum calculation procedure. The above collective behavior is likely resulted from interelectron co...The manuscript deals with the possibility of application of collective behavior of quantum particles to realize the quantum calculation procedure. The above collective behavior is likely resulted from interelectron correlations, characteristic for strongly correlated systems containing atoms with unoccupied 3d-, 4f- and 5f- shells. Among such systems can be the heterospin systems, complexes of paramagnetic ions of transition metals with organic radicals, because for such objects, spin-spin interaction between unpaired electron spins of different paramagnetic centers is typical. To apply the aforementioned possibility for the organization of real quantum calculations, it is necessary to synthesize such paramagnetic molecules （paramagnetic clusters）, where the entangled states will be realized naturally by self-organization of atoms incorporated in these molecules, i.e., without additional external effect of q-bits on the system. The specified self-organization may be due to intramolecular processes and, in particular, intramolecular rearrangement called valence tautomerism, which leads to heterogeneous magnetic states, i.e., to phase layering in paramagnetic cluster owing to interelectron correlations. The states realized during the phase layering can be used for coding the digits. Since such states correspond to specific structures of para-magnetic molecule, they can exist as much as long under certain conditions. In turn, it means that the account of the interelectron correlations, which take place in strongly correlated compounds, allows （at least, in principle） one to create elementary quantum bit of the information capable of modeling the elementary logical operations. Creation of a network of such quantum bits combined in a certain sequence should be considered as a practical step on a way to experimental realization of the idea of quantum computer creation. The group consisting of three quantum points can make the basis of quantum computer. In such a gate, quantum points can be connected via the interaction modeled by spin-spin interaction, characteristic for ABX system in NMR spectroscopy. The tunnel effect, which can be easily realized and controlled, can act as an indicator of bonding in such a block. The calculation procedure can be organized assuming that the initial state of the group corresponds to 1. Infringement of such a state indicates to zero （or, on the contrary）. Thus, the calculation in the binary system becomes organized. The creation of a network on the basis of combination of such processors in certain sequence should be considered as a practical step on a way to experimental realization of the idea of the quantum computer creation.展开更多
基金supported by the National Natural Science Foundation of China(21376235)Natural Science Foundation of Liaoning Province(201602740)~~
文摘The synthesis of ferrierite(FER)zeolite using piperidine as an organic structure‐directing agent was investigated.X‐ray diffraction,X‐ray fluorescence,N2‐adsorption,and scanning electron microscopy were used to characterize the crystal phases,textural properties,and particle morphologies of the zeolite samples.The crystallization behavior of the FER zeolite was found to be directly related to crystallization temperature.At150?C,pure FER phase was observed throughout crystallization.At160–170?C,MWW phase appeared first and gradually transformed into FER phase over time,indicating that the FER phase was thermodynamically favored.In the piperidine‐Na2O‐H2O synthetic system,alkalinity proved to be the crucial factor determining the size and textural properties of FER zeolite.Furthermore,the obtained FER samples exhibited good catalytic performance in the skeletal isomerization of1‐butene.
基金supported by the National Natural Science Foundation of China(21776295)the Youth Innovation Promotion Association,CAS(2017355)~~
文摘A novel melting-assisted solvent-free route using solid oxalic acid was proposed for the post-treatment of SAPO-11 zeolite,followed by loading with 0.5 wt%Pt by the incipient wetness impregnation method.Subsequently,the performance of the obtained bifunctional catalysts toward the hydroisomerization of n-dodecane was examined.The prepared samples were characterized by XRD,SEM,BET,XRF,Py-IR,and solid-state NMR.From the results,it was found that the high crystallinity and uniform morphology were retained after the post-treatment and that more(002)crystal faces were exposed,which was beneficial since more acid sites were provided.More importantly,the total Bronsted acid sites and the ratio(Ra)of the micropore area to the total surface area were optimized by this method.Thus,the catalytic performance was enhanced significantly,and the prepared Pt-SAPO-11-10%catalyst had the highest i-dodecane yield of 80.1%compared to 55.3%of Pt-SAPO-11.Expectedly,this facile and cost-effective method is promising for the hydroisomerization of normal paraffin in the production of lubricant base oils.
文摘Energy raolved mass spectra (ERMS) of 2, 3-DNT and 3, 5-DNT isomers was mported. The fragmentation of this pair of DNTisomers was studied by ERMS in electron impact (EI),and their breakdown curves were discussed , These nitraromaic isomers can be characterized according to the differences between their ERMS in MS/MS
文摘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.
文摘Metal-loaded zeolite catalysts were synthesized and examined in the hydroisomerization of n-decane.Specifically,zeolite Y was impregnated with 0.1 wt%Pd and varying amounts of Ni（0.1-0.5 wt%].The crystallinity of the metal-loaded catalysts was characterized by X-ray diffraction,and the average metal particle size was determined by transmission electron microscopy.The states of Pd and Ni were identified by X-ray photoelectron spectroscopy.Ammonia temperature-programmed desorption analysis revealed the occurrence of ion-exchange of some of the catalyst acid sites with Ni-（2＋）.The reducibility of the HY zeolite-supported Pd,Ni,and Pd-Ni catalysts was studied by temperature-programmed reduction.The hydroisomerization of n-decane over the prepared catalyst was conducted at 200-450℃ under 1 atm.Ni addition of up to 0.3 wt%over 0.1 wt%Pd/HY enhanced the n-decane conversion and isomerization product selectivity.The improved selectivity of the mono- and dibranched isomers suggested the occurrence of a protonated cyclopropane intermediate mechanism.However,further Ni addition above 0.3 wt%considerably reduced the activity and isomerization selectivity.The bimetallic catalysts were more selective toward the formation of dibranched isomers,i.e.,those containing a higher octane number.
基金Supported by Chinese Basic Research Project (G1999012007) and Na-tional Natural Science Foundation of China (No. 39700017).
文摘To compare genetic markers for population genetics analysis, allozyme electrophoresis and random amplified polymorphic DNA （RAPD） were used to detect the genetic structure of scallop Chlamysfarreri population. Thirteen enzymes （MDH, ME, IDH, GPI, PGM, PEP-LG, PEP-pp, ACP, AK, PK, AAT, SOD, EST） in three butter systems （TC, pH6.9; TMME, pH 7.4; and EBT, pHS.9） were selected and 22 loci were used for the analysis, among them 7 loci （Gpi, Pgm, Pep.m-l, Pep.pp. Aat-2, Est-2, Est-3） were polymorphic which attributed 31.82% to the total. The average of heterozygosity was 0.113 and most of the studied loci showed heterozygote deficiencies. The same specimens were investigated using 10 arbitrarily selected primers （10-base）. Twenty two of 54 RAPD fragments were polymorphic with average heterozygosity of 0.194. The result indicated that the two types of markers reflected a consistent trend in the parameter values of genetic diversity of the population, but RAPD revealed more information of genetic variation than allozyme electrophoresis.
文摘The aromaticity of all possible substituted fullerene isomers of C18N2, C18B2, C18BN, and their molecular ions which originate from the C20 （Ih） cage were studied by the topological resonance energy （TRE） and the percentage topological resonance energy methods. The relationship between the aromaticity of C18BxNy isomers and the sites where the heteroatoms dope at the C20 （Ih） cage is discussed. Calculation results show that at the neutral and cationic states all the isomers are predicted to be antiaromatic with negative TREs, but their polyvalent anions are predicted to be aromatic with positive TREs. The most stable isomer is formed by heteroatom doping at the 1,11-sites in C18N2. C18B2, and C18BN. Heterofullerenes are more aromatic than C20. The stability order in the neutral states is C18N2〉C18BN〉C18B2〉C20. The stability order in closed-shell is C18B2^8- 〉C20^6- 〉C18BN^6- 〉C18N2^4-. This predicts theoretically that their polyvalent anions have high aromaticity.
基金This work was supported by the National Natural Science Foundation of China （No.20336010） and the State Key Basic Research and Development Plan of China （No.2003CB716000）.
文摘The complex model of Thermus thermophilus xylose isomerase （TtXI） with D-xylose was constructed, and molecular dynamics （MD） simulations were carried out at 300 and 360 K for 10 ns by NAMD2.5. The radius of gyration （Rg）, subunit interactions, and residue flexibility were analyzed. The results show that residues 60-69, 142-148, 169-172, and 332-340 have high flexibility at 300 and 360 K. Residues with higher flexibility at 360 K than that at 300 K can mainly be divided into two groups： one locates in the helix-loophelix region consisting of residues 55-80 in catalytic domain; the other at subunit interfaces. The Rg of catalytic domain at 360 K shows 0.16 A higher than that at 300 K, but Rg of small C-terminal domain has no obvious difference. The results indicate that enhanced Rg of catalytic domain may lead to the intense motion of the active site of TtXI and promote the D-xylose isomization reaction. Eight hydrogen bonds and five ion pairs are reduced at subunit interfaces at 360 K compared with 300 K, that may be the main reason for the decrease in rigidity and increase in activity at high temperature of TtXI. This result also help to explain the cold-adaption phenomenon of TtXI E372G mutant reported previously. Our results reveal the relationship between temperature and structure flexibility of TtXI, and play an important role in understanding the thermostability of thermophile protein with multiple subunits.
基金supported by the National Natural Science Foundation of China (21641011, 21773313)the Natural Science Foundation of Fujian Province (2015J01053, 2016J01060)+1 种基金Program for New Century Excellent Talents in Fujian Province UniversityPromotion Program for Young and Middle-aged Teacher in Science, Technology Research of Huaqiao University (ZQN-PY104)~~
文摘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.
文摘The rational design of photochemical molecular device(PMD)and its hybrid system has great potential in improving the activity of photocatalytic hydrogen production.A series of Pd6L3 type metal-organic cages,denoted as MOC-Py-M(M=H,Cu,and Zn),are designed for PMDs by combining metalloporphyrin-based ligands with catalytically active Pd^(2+)centers.These metal-organic cages(MOCs)are first successfully hybridized with graphitic carbon nitride(g-C_(3)N_(4))to form direct Z-scheme heterogeneous MOC-Py-M/g-C_(3)N_(4)(M=H,Cu,and Zn)photocatalysts via π-πinteractions.Benefiting from its better light absorption ability,the MOC-Py-Zn/g-C_(3)N_(4) catalyst exhibits high H_(2) production activity under visible light(10348μmol g^(-1) h^(-1)),far superior to MOC-Py-H/g-C_(3)N_(4) and MOC-Py-Cu/g-C_(3)N_(4).Moreover,the MOC-Py-Zn/g-C_(3)N_(4) system obtains an enhanced turn over number(TON)value of 32616 within 100 h,outperforming the homogenous MOC-Py-Zn(TON of 507 within 100 h),which is one of the highest photochemical hybrid systems based on MOC for visible-light-driven hydrogen generation.This confirms the direct Z-scheme heterostructure can promote effective charge transfer,expand the visible light absorption region,and protect the cages from decomposition in MOC-Py-Zn/g-C_(3)N_(4).This work presents a creative example that direct Z-scheme PMD-based systems for effective and persistent hydrogen generation from water under visible light are obtained by heterogenization approach using homogeneous porphyrin-based MOCs and g-C_(3)N_(4) semiconductors.
文摘Investigations show that in monomer water heterogeneous systems polymerization, located in the interface, can disperse the system. Following polymerization in the density gradient field it is shown that in such systems latex particles are nucleated from monomer microdroplets, containing a certain amount of polymer molecules. It could be considered that, independently of the nature of the monomer itself, polymerization in monomer water statistic heterogeneous systems modulate emulsion polymerization process.
文摘Exo-tetrahydrodicyclopentadiene （exo-TCD） is an important high-energy fuel. Silicotungstic acid （SiW） immobilized on H-type β zeolite （Hβ） at room temperature were used to prepare the Hβ zeolite catalysts with different SiW contents. Catalytic performances of the catalysts were investigated during the preparation of exo-TCD via isomerization of endo-tetrahydrodicyclopentadiene （endo-TCD）. The properties of catalysts were characterized by XRD, temperature pro- grammed desorption of ammonia （NHa-TPD）, FT-IR, and N2-adsorption techniques. SiW was highly dispersed on the surface of Hβ zeolite, and the 10% SiW/Hβ zeolite catalyst had the highest amount of weak acidity among all SiW/Hβ zeolite catalysts. The influence of different factors on isomerization reaction was investigated. At a reaction temperature of 240 ℃, a n（cyclohexane） / n（endo-TCD） ratio of 10, a m（catalyst）/m（endo-TCD） ratio of 0.3, an initial pressure of 1.0 MPa, and a reaction time of 1.5 h in the presence of 10% SiW/Hβ catalyst calcined at 400 ℃, the conversion of endo-TCD reached up to 92.0%, with the yield of exo-TCD equating to 51.0%.
文摘The performance of MCM-22 zeolite for catalytic isomerization of 1-hexene has been studied. At a n(H2)/n(1-hexene) ratio of 8, the influence of steam treatment temperature, reaction temperature and reaction pressure on the performance of MCM-22 zeolite for catalytic skeletal isomerization of 1-hexene was examined. The experimental results showed that at a steam treatment temperature of 500℃, a reaction temperature of 270℃, a space velocity of 1.0 h-1 and a reaction pressure of 0.2 MPa, the MCM-22 zeolite exhibited excellent performance for catalytic skeletal isomerization of 1-hexene with the i-hexene yield reaching 66.15%. Compared with other commonly used molecular sieve catalysts, the MCM-22 zeolite catalyst exhibited better catalytic performance for skeletal isomerization of 1-hexene.
文摘A study of the influence of magnetic field on the tautomerism, the authors proposed a new method for predicting possible new intra- and intermolecular rearrangements due to tautomerism. The authors have proposed a general mechanism of possible rearrangements and tautomerism.
文摘The manuscript deals with the possibility of application of collective behavior of quantum particles to realize the quantum calculation procedure. The above collective behavior is likely resulted from interelectron correlations, characteristic for strongly correlated systems containing atoms with unoccupied 3d-, 4f- and 5f- shells. Among such systems can be the heterospin systems, complexes of paramagnetic ions of transition metals with organic radicals, because for such objects, spin-spin interaction between unpaired electron spins of different paramagnetic centers is typical. To apply the aforementioned possibility for the organization of real quantum calculations, it is necessary to synthesize such paramagnetic molecules （paramagnetic clusters）, where the entangled states will be realized naturally by self-organization of atoms incorporated in these molecules, i.e., without additional external effect of q-bits on the system. The specified self-organization may be due to intramolecular processes and, in particular, intramolecular rearrangement called valence tautomerism, which leads to heterogeneous magnetic states, i.e., to phase layering in paramagnetic cluster owing to interelectron correlations. The states realized during the phase layering can be used for coding the digits. Since such states correspond to specific structures of para-magnetic molecule, they can exist as much as long under certain conditions. In turn, it means that the account of the interelectron correlations, which take place in strongly correlated compounds, allows （at least, in principle） one to create elementary quantum bit of the information capable of modeling the elementary logical operations. Creation of a network of such quantum bits combined in a certain sequence should be considered as a practical step on a way to experimental realization of the idea of quantum computer creation. The group consisting of three quantum points can make the basis of quantum computer. In such a gate, quantum points can be connected via the interaction modeled by spin-spin interaction, characteristic for ABX system in NMR spectroscopy. The tunnel effect, which can be easily realized and controlled, can act as an indicator of bonding in such a block. The calculation procedure can be organized assuming that the initial state of the group corresponds to 1. Infringement of such a state indicates to zero （or, on the contrary）. Thus, the calculation in the binary system becomes organized. The creation of a network on the basis of combination of such processors in certain sequence should be considered as a practical step on a way to experimental realization of the idea of the quantum computer creation.
