The reductive cyclocoupling of isocyanides is a pivotal reaction that facilitates the rapid construction of intricate cyclic compounds in a single-step process.In this work,treatment of simple precursor1(Cp^(#)CrLCl,L...The reductive cyclocoupling of isocyanides is a pivotal reaction that facilitates the rapid construction of intricate cyclic compounds in a single-step process.In this work,treatment of simple precursor1(Cp^(#)CrLCl,L=CAAC,NHC,PCy_(3),or PPh_(2)Et;Cp^(#)=Cp^(*)or Cp^(*TMS))with XylNC(2,6-dimethylphenyl isocyanide)led to the reductive coupling of isocyanides,yielding either complex 2{(Cp^(*TMS)Cr)_(2)[μ-C_(4)(NXyl)_(4)]}or complex 6{(Cp^(*)CrCl)_(2)[μ-C_(4)(NXyl)_(4)]},corresponding to the tetramerization of isocyanides.Control experiments and in-situ monitoring were carried out to understand the reaction mechanism,revealing various side reaction pathways during the isocyanide tetramerization.SQUID and DFT calculations provided insights into the electronic structures.In complex 2,the energies of nonet and broken-symmetry singlet states are close and significantly lower than other spin states,indicating two independent highspin Cr(Ⅱ)centers with weak antiferromagnetic coupling.A similar situation is observed in complex 6,where two independent high-spin Cr(Ⅲ)centers are coupled antiferromagnetically.In both complexes 2 and 6,the tetrameric isocyanide rings,receiving two electrons from Cr centers,show averaged bond lengths and display moderate aromatic characteristics.展开更多
A new isopropenyl benzofuran-type tetramer was isolated from the roots of ligularia stenocephala and its structure was established by spectroscopic methods.
A hydrothermal reaction of copper acetate with ammonium molybdate, 4,4-bpy (4,4-bipyridine) and 1,10-phen (1,10-phenanthroline) led to the formation of brown crystals of [Cu2(1,10-phen)2(4,4-bpy)]2 [Mo8O26]4H2O 1. Si...A hydrothermal reaction of copper acetate with ammonium molybdate, 4,4-bpy (4,4-bipyridine) and 1,10-phen (1,10-phenanthroline) led to the formation of brown crystals of [Cu2(1,10-phen)2(4,4-bpy)]2 [Mo8O26]4H2O 1. Single-crystal X-ray analysis has revealed that 1 (C68H56N12O30Cu4Mo8) crystallizes in the triclinic system, space group P with a = 11.270(3), b = 13.113(6), c = 13.906(3) ? = 103.33(4), b = 98.54(2), g = 101.29(2)? V = 1920.1(1) ?3, Mr = 2542.93, Z = 1, Dc = 2.199 g/cm3, m = 2.435 mm-1, F(000) = 1240, the final R = 0.0445, wR = 0.1082 and S = 1.021 for 5052 observed reflections with I >2s(I). It consists of copper (Ⅰ) tetramer units and -[Mo8O26]4- anions, which are further attached into a three-dimensional framework through hydrogen bonding and - stacking interactions.展开更多
Two novel diphoshinoamine ligands have been synthesized. Combination of Cr（Ⅲ） and methylaluminoxane（MAO） generated active catalytic system which can catalyze tetramerization of ethylene with high catalytic activi...Two novel diphoshinoamine ligands have been synthesized. Combination of Cr（Ⅲ） and methylaluminoxane（MAO） generated active catalytic system which can catalyze tetramerization of ethylene with high catalytic activity up to 2.5×10^6 g/mol Cr.h and high selectivity to produce 1-octene （Cs in products is being 89.80 wt%）.展开更多
N-acetylatedα-synuclein(αSyn)has long been established as an intrinsically disordered protein associated with a dysfunctional role in Parkinson’s disease.In recent years,a physiologically relevant,higher order conf...N-acetylatedα-synuclein(αSyn)has long been established as an intrinsically disordered protein associated with a dysfunctional role in Parkinson’s disease.In recent years,a physiologically relevant,higher order conformation has been identified as a helical tetramer that is tailored by buried hydrophobic interactions and is distinctively aggregation resistant.The canonical mechanism by which the tetramer assembles remains elusive.As novel biochemical approaches,computational methods,pioneering purification platforms,and powerful imaging techniques continue to develop,puzzling information that once sparked debate as to the veracity of the tetramer has now shed light upon this new counterpart inαSyn neurobiology.Nuclear magnetic resonance and computational studies on multimericαSyn structure have revealed that the protein folding propensity is controlled by small energy barriers that enable large scale reconfiguration.Alternatively,familial mutations ablate tetramerization and reconfigure polymorphic fibrillization.In this review,we will discuss the dynamic landscape ofαSyn quaternary structure with a focus on the tetrameric conformation.展开更多
Helicobacter pylori 3-Deoxy-D-manno-2-octulosonate-8-phosphate (KDO8P) synthase catalyzes the conversion of D-arabinose-5-phosphate (A5P) and phosphoenolpyruvate (PEP)
Chromium acetylacetonate and bis(diphenylphosphino)isopropylamine were coordinated in situ and supported on methylaluminoxane-modified silica. The catalyst structure and effects of reaction temperature, reaction press...Chromium acetylacetonate and bis(diphenylphosphino)isopropylamine were coordinated in situ and supported on methylaluminoxane-modified silica. The catalyst structure and effects of reaction temperature, reaction pressure and Al/Cr molar ratio on ethylene tetramerization were investigated in detail. Chromium was uniformly and firmly immobilized on the support and could not be leached off by methylaluminoxane. The supported catalyst, upon being activated with methylaluminoxane, exhibited catalytic activity of 1.70×107 g/(mol Cr·h) for ethylene tetramerization to form 1-octene at a reaction temperatures of 80 ℃, a pressure of 2.0 MPa and an Al/Cr molar ratio of 300. The supported catalyst presented a good tolerance to high temperature.展开更多
We investigate the quantum phase transition(QPT) and magnetocaloric effect(MCE) of a tetrameric chain with three-spin interaction using Green's function theory. The magnetization and gap analysis reveals a variety...We investigate the quantum phase transition(QPT) and magnetocaloric effect(MCE) of a tetrameric chain with three-spin interaction using Green's function theory. The magnetization and gap analysis reveals a variety of quantum phases tuned by magnetic field and three-spin interaction, which can open up an energy gap, giving rise to the occurrence of zero magnetization plateau. However, strong three-spin couplings causing strong frustration will destroy the intermediate 1/2 plateau with emergence of a new gapless phase between two cusps. It favors achieving an enhanced MCE at the critical fields, where the minima of isoentropes as well as the valley-peak structure of Gru¨neisen ratio, signaling the accumulation of entropy, lead to cooling via adiabatic(de)magnetization processes. It is also found that the temperature dependence of specific heat combined with Gru¨neisen ratio can testify various quantum phases explicitly.展开更多
A new resveratrol tetramer, sinicin A was isolated from the roots of Ampelopsis sinica, with four known tetramers: vitisin A, cis-vitisin B, ampelopsin H and hopeaphenol. The structure and stereochemistry of sinicin A...A new resveratrol tetramer, sinicin A was isolated from the roots of Ampelopsis sinica, with four known tetramers: vitisin A, cis-vitisin B, ampelopsin H and hopeaphenol. The structure and stereochemistry of sinicin A have been established on the basis of 1D and 2D NMR spectroscopic techniques.展开更多
A new mixed-ligand Zn（II） complex, [Zn（4,4′-bipy）2（H2O）4]-2ANS·6H2O （1, 4,4′- bipy = 4,4′-bipyridine, HANS = 2-aminonaphthalene-l-sulfonic acid）, has been isolated and structurally characterized by sin...A new mixed-ligand Zn（II） complex, [Zn（4,4′-bipy）2（H2O）4]-2ANS·6H2O （1, 4,4′- bipy = 4,4′-bipyridine, HANS = 2-aminonaphthalene-l-sulfonic acid）, has been isolated and structurally characterized by single-crystal X-ray diffwaction, FT-IR spectrum, TG and elemental analysis. It crystallizes in the monoclinic system, space group P2 1/c with a = 12.4852（8）, b = 18.3163（12）, c = 10.9707（7） A, β = 114.2600（10）°, V= 2287.3（3） A3, Dc = 1.455 g/cm3, Mr = 1002.37, Z = 2, F（000） = 1048,μ = 0.704 mm＂1, the final R = 0.0408 and wR = 0.962 for 4029 observed reflections with I 〉 2σ（I）. Interestingly, an unusual one-dimensional （1D） water tape with cyclic tetrameric water clusters can be observed in 1, which are further trapped via Zn-O coordination bonds exhibiting a 2D Zn（Ⅱ）-water layer. These 2D Zn（Ⅱ）-water layers are stacked together into a 3D interdigitated supramolecular architecture via weak π…π interactions, in which free ANS anions are tightly filled by hydrogen-bonding interactions. Thus, π…π and classical hydrogen-bonding interactions are fotmd as main driving forces to stabilize the 2D Zn（Ⅱ）-water layers.展开更多
Analysis of the frequency of antigen-specific cytotoxic T lymphocytes (CTLs) ex vivo is largely dependent on the use of MHC/peptide tetramers. However, the latter reagents have not been widely available, most likely b...Analysis of the frequency of antigen-specific cytotoxic T lymphocytes (CTLs) ex vivo is largely dependent on the use of MHC/peptide tetramers. However, the latter reagents have not been widely available, most likely because of their costly and time-consuming production. In this report we utilized an economic strategy to construct HLA/peptide tetramers with recombinant peptide-linked β2 microglobulin (β2m). The HLA-A2-restricted, melanoma antigen MARTI-derived pep- tide MART127-35( AAGIGILTV) was fused to the N terminus of human β2m through a 15-amino acid (aa)-long linker before being refolded with the recombinant biotinylated HLA-A2 heavy chain ectodomain. The resulted 2-component (2C) monomer was then tetramerized with phycoerythin-labeled streptavidin. The experimental result showed that the 2C HLA-A2/ MART127-35 monomer was shown to bind to the HLA class complex-specific monoclonal antibody W6/32 and the HLA-A2/ MART127-35 complex-specific single chain antibody fragment (scFv) 8.3, suggesting the correctness of its specificity. Fur- thermore, the 2C HLA-A2/MART127-35 tetramer detected a specific CD8+ T cell population in HLA-A2-restricted melanoma infiltrating lymphocytes as the conventional 3C HLA-A2/MART127-35 tetramer. The yield of 2C HLA-A2/MART127-35 monomer was 2. 5 times more than that of the conventional 3C monomer. Taken together, these data indicate that the HLA-A2/ MART127-35 tetramer can be generated conveniently through the use of MART127-35 peptide-β2 m fusion proteins, which can fa- cilitate the monitoring of HLA-A2-restricted, MART1-specific CTL responses in patients with melanoma.展开更多
Natural killer(NK)cells are cytotoxic innate lymphocytes crucial for rapid immune responses against pathogens and tumors[1].A dynamic network of transcription factors(TFs)orchestrates NK cell specification,development...Natural killer(NK)cells are cytotoxic innate lymphocytes crucial for rapid immune responses against pathogens and tumors[1].A dynamic network of transcription factors(TFs)orchestrates NK cell specification,development,and maturation in a sequential,coordinated manner[2].展开更多
基金the financial support by the National Natural Science Foundation of China(No.22201013)。
文摘The reductive cyclocoupling of isocyanides is a pivotal reaction that facilitates the rapid construction of intricate cyclic compounds in a single-step process.In this work,treatment of simple precursor1(Cp^(#)CrLCl,L=CAAC,NHC,PCy_(3),or PPh_(2)Et;Cp^(#)=Cp^(*)or Cp^(*TMS))with XylNC(2,6-dimethylphenyl isocyanide)led to the reductive coupling of isocyanides,yielding either complex 2{(Cp^(*TMS)Cr)_(2)[μ-C_(4)(NXyl)_(4)]}or complex 6{(Cp^(*)CrCl)_(2)[μ-C_(4)(NXyl)_(4)]},corresponding to the tetramerization of isocyanides.Control experiments and in-situ monitoring were carried out to understand the reaction mechanism,revealing various side reaction pathways during the isocyanide tetramerization.SQUID and DFT calculations provided insights into the electronic structures.In complex 2,the energies of nonet and broken-symmetry singlet states are close and significantly lower than other spin states,indicating two independent highspin Cr(Ⅱ)centers with weak antiferromagnetic coupling.A similar situation is observed in complex 6,where two independent high-spin Cr(Ⅲ)centers are coupled antiferromagnetically.In both complexes 2 and 6,the tetrameric isocyanide rings,receiving two electrons from Cr centers,show averaged bond lengths and display moderate aromatic characteristics.
基金supoaed by the National Natural Science Foundation of China(No.29972017)
文摘A new isopropenyl benzofuran-type tetramer was isolated from the roots of ligularia stenocephala and its structure was established by spectroscopic methods.
基金This work was supported by the National Natural Science Foundation of China (20073048) NSF of Fujian and the Chinese Academy of Sciences
文摘A hydrothermal reaction of copper acetate with ammonium molybdate, 4,4-bpy (4,4-bipyridine) and 1,10-phen (1,10-phenanthroline) led to the formation of brown crystals of [Cu2(1,10-phen)2(4,4-bpy)]2 [Mo8O26]4H2O 1. Single-crystal X-ray analysis has revealed that 1 (C68H56N12O30Cu4Mo8) crystallizes in the triclinic system, space group P with a = 11.270(3), b = 13.113(6), c = 13.906(3) ? = 103.33(4), b = 98.54(2), g = 101.29(2)? V = 1920.1(1) ?3, Mr = 2542.93, Z = 1, Dc = 2.199 g/cm3, m = 2.435 mm-1, F(000) = 1240, the final R = 0.0445, wR = 0.1082 and S = 1.021 for 5052 observed reflections with I >2s(I). It consists of copper (Ⅰ) tetramer units and -[Mo8O26]4- anions, which are further attached into a three-dimensional framework through hydrogen bonding and - stacking interactions.
文摘Two novel diphoshinoamine ligands have been synthesized. Combination of Cr（Ⅲ） and methylaluminoxane（MAO） generated active catalytic system which can catalyze tetramerization of ethylene with high catalytic activity up to 2.5×10^6 g/mol Cr.h and high selectivity to produce 1-octene （Cs in products is being 89.80 wt%）.
基金supported in part by Award No.18-7(to HRL)from the Commonwealth of Virginia’s Alzheimer’s and Related Diseases Research Award Fund,administered by the Virginia Center on Aging
文摘N-acetylatedα-synuclein(αSyn)has long been established as an intrinsically disordered protein associated with a dysfunctional role in Parkinson’s disease.In recent years,a physiologically relevant,higher order conformation has been identified as a helical tetramer that is tailored by buried hydrophobic interactions and is distinctively aggregation resistant.The canonical mechanism by which the tetramer assembles remains elusive.As novel biochemical approaches,computational methods,pioneering purification platforms,and powerful imaging techniques continue to develop,puzzling information that once sparked debate as to the veracity of the tetramer has now shed light upon this new counterpart inαSyn neurobiology.Nuclear magnetic resonance and computational studies on multimericαSyn structure have revealed that the protein folding propensity is controlled by small energy barriers that enable large scale reconfiguration.Alternatively,familial mutations ablate tetramerization and reconfigure polymorphic fibrillization.In this review,we will discuss the dynamic landscape ofαSyn quaternary structure with a focus on the tetrameric conformation.
文摘Helicobacter pylori 3-Deoxy-D-manno-2-octulosonate-8-phosphate (KDO8P) synthase catalyzes the conversion of D-arabinose-5-phosphate (A5P) and phosphoenolpyruvate (PEP)
基金supported by the National Natural Science Foundation of China (U1162114)the PetroChina Innovation Foundation (2012D-5006-0501)+2 种基金the Tianjin Municipal Education Commission of China (20110505)the Natural Science Foundation of Tianjin (12JCQNJC06000)the Program for New Century Excellent Talents in University (NCET-07-0142)
文摘Chromium acetylacetonate and bis(diphenylphosphino)isopropylamine were coordinated in situ and supported on methylaluminoxane-modified silica. The catalyst structure and effects of reaction temperature, reaction pressure and Al/Cr molar ratio on ethylene tetramerization were investigated in detail. Chromium was uniformly and firmly immobilized on the support and could not be leached off by methylaluminoxane. The supported catalyst, upon being activated with methylaluminoxane, exhibited catalytic activity of 1.70×107 g/(mol Cr·h) for ethylene tetramerization to form 1-octene at a reaction temperatures of 80 ℃, a pressure of 2.0 MPa and an Al/Cr molar ratio of 300. The supported catalyst presented a good tolerance to high temperature.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11204157,11174179,11247020the China Three Gorges University Project KJ2011B068
文摘We investigate the quantum phase transition(QPT) and magnetocaloric effect(MCE) of a tetrameric chain with three-spin interaction using Green's function theory. The magnetization and gap analysis reveals a variety of quantum phases tuned by magnetic field and three-spin interaction, which can open up an energy gap, giving rise to the occurrence of zero magnetization plateau. However, strong three-spin couplings causing strong frustration will destroy the intermediate 1/2 plateau with emergence of a new gapless phase between two cusps. It favors achieving an enhanced MCE at the critical fields, where the minima of isoentropes as well as the valley-peak structure of Gru¨neisen ratio, signaling the accumulation of entropy, lead to cooling via adiabatic(de)magnetization processes. It is also found that the temperature dependence of specific heat combined with Gru¨neisen ratio can testify various quantum phases explicitly.
基金This research program was supported by the National Natural Science Foundation of China (No. 30070+2 种基金889). The authors thank the Department of Instrumental Analysis Institute of Materia Medica Chinese Academy of Medical Sciences & Peking Union Col
文摘A new resveratrol tetramer, sinicin A was isolated from the roots of Ampelopsis sinica, with four known tetramers: vitisin A, cis-vitisin B, ampelopsin H and hopeaphenol. The structure and stereochemistry of sinicin A have been established on the basis of 1D and 2D NMR spectroscopic techniques.
基金Supported by the Advanced Project for Young Teachers in Tianjin Normal University
文摘A new mixed-ligand Zn（II） complex, [Zn（4,4′-bipy）2（H2O）4]-2ANS·6H2O （1, 4,4′- bipy = 4,4′-bipyridine, HANS = 2-aminonaphthalene-l-sulfonic acid）, has been isolated and structurally characterized by single-crystal X-ray diffwaction, FT-IR spectrum, TG and elemental analysis. It crystallizes in the monoclinic system, space group P2 1/c with a = 12.4852（8）, b = 18.3163（12）, c = 10.9707（7） A, β = 114.2600（10）°, V= 2287.3（3） A3, Dc = 1.455 g/cm3, Mr = 1002.37, Z = 2, F（000） = 1048,μ = 0.704 mm＂1, the final R = 0.0408 and wR = 0.962 for 4029 observed reflections with I 〉 2σ（I）. Interestingly, an unusual one-dimensional （1D） water tape with cyclic tetrameric water clusters can be observed in 1, which are further trapped via Zn-O coordination bonds exhibiting a 2D Zn（Ⅱ）-water layer. These 2D Zn（Ⅱ）-water layers are stacked together into a 3D interdigitated supramolecular architecture via weak π…π interactions, in which free ANS anions are tightly filled by hydrogen-bonding interactions. Thus, π…π and classical hydrogen-bonding interactions are fotmd as main driving forces to stabilize the 2D Zn（Ⅱ）-water layers.
文摘Analysis of the frequency of antigen-specific cytotoxic T lymphocytes (CTLs) ex vivo is largely dependent on the use of MHC/peptide tetramers. However, the latter reagents have not been widely available, most likely because of their costly and time-consuming production. In this report we utilized an economic strategy to construct HLA/peptide tetramers with recombinant peptide-linked β2 microglobulin (β2m). The HLA-A2-restricted, melanoma antigen MARTI-derived pep- tide MART127-35( AAGIGILTV) was fused to the N terminus of human β2m through a 15-amino acid (aa)-long linker before being refolded with the recombinant biotinylated HLA-A2 heavy chain ectodomain. The resulted 2-component (2C) monomer was then tetramerized with phycoerythin-labeled streptavidin. The experimental result showed that the 2C HLA-A2/ MART127-35 monomer was shown to bind to the HLA class complex-specific monoclonal antibody W6/32 and the HLA-A2/ MART127-35 complex-specific single chain antibody fragment (scFv) 8.3, suggesting the correctness of its specificity. Fur- thermore, the 2C HLA-A2/MART127-35 tetramer detected a specific CD8+ T cell population in HLA-A2-restricted melanoma infiltrating lymphocytes as the conventional 3C HLA-A2/MART127-35 tetramer. The yield of 2C HLA-A2/MART127-35 monomer was 2. 5 times more than that of the conventional 3C monomer. Taken together, these data indicate that the HLA-A2/ MART127-35 tetramer can be generated conveniently through the use of MART127-35 peptide-β2 m fusion proteins, which can fa- cilitate the monitoring of HLA-A2-restricted, MART1-specific CTL responses in patients with melanoma.
基金supported in part by grants Biological BreedingMajor Projects(2023ZD04050 and 2023ZD04070)the National Natural Scientific Foundation of China(32130039 and 31970831)+3 种基金the National Key Research and Development Program of China(2024YFA1802400 and 2023YFF1000901)“Hundred”Level Of High-Level Innovative Talents in Guizhou Province(GCC[2023]040)the Pinduoduo-China Agricultural University Research Fund(PC2023B01011)the Innovation Program of Chinese Academy of Agricultural Sciences(CAAS-CSAB-202401).
文摘Natural killer(NK)cells are cytotoxic innate lymphocytes crucial for rapid immune responses against pathogens and tumors[1].A dynamic network of transcription factors(TFs)orchestrates NK cell specification,development,and maturation in a sequential,coordinated manner[2].
