The genomes of eukaryotic cells are under continuous assault by environmental agents and endogenous metabolic byproducts. Damage induced in DNA usually leads to a cascade of cellular events, the DNA damage response. F...The genomes of eukaryotic cells are under continuous assault by environmental agents and endogenous metabolic byproducts. Damage induced in DNA usually leads to a cascade of cellular events, the DNA damage response. Failure of the DNA damage response can lead to development of malignancy by reducing the efficiency and fidelity of DNA repair. The NBS1 protein is a component of the MRE11/RAD50/NBS 1 complex （MRN） that plays a critical role in the cellular response to DNA damage and the maintenance of chromosomal integrity. Mutations in the NBS1 gene are responsible for Nijmegen breakage syndrome （NBS）, a hereditary disorder that imparts an increased predisposition to development of malignancy. The phenotypic characteristics of cells isolated from NBS patients point to a deficiency in the repair of DNA double strand breaks. Here, we review the current knowledge of the role of NBS1 in the DNA damage response. Emphasis is placed on the role of NBS1 in the DNA double strand repair, modulation of the DNA damage sensing and signaling, cell cycle checkpoint control and maintenance oftelomere stability.展开更多
AIM To determine the prevalence and diagnostic value of autoantibodies inα-fetoprotein(AFP)-negative hepatocellular carcinoma(HCC).METHODS Fifty-six serum samples from AFP-negative HCC cases,86 from AFP-positive HCC ...AIM To determine the prevalence and diagnostic value of autoantibodies inα-fetoprotein(AFP)-negative hepatocellular carcinoma(HCC).METHODS Fifty-six serum samples from AFP-negative HCC cases,86 from AFP-positive HCC cases,168 from chronic liver disease cases,and 59 from normal human controls were included in this study.Autoantibodies to nucleophosmin(NPM)1,14-3-3zeta and mouse double minute 2 homolog(MDM2)proteins in AFP-negative HCC serum were evaluated by enzymelinked im munosorbent assay.Partially positive sera were further evaluated by western blotting.Immunohistochemistry was used to detect the expression of three tumor-associated antigens(TAAs)in AFP-negative HCC and normal control tissues.RESULTS The frequency of autoantibodies to the three TAAs in AFP-negative HCC sera was 21.4%,19.6%and 19.6%,which was significantly higher than in the chronic liver disease cases and normal human controls(P<0.01)as well as AFP-positive HCC cases.The sensitivity of the three autoantibodies for diagnosis of AFP-negative HCC ranged from 19.6%to 21.4%,and the specificity was approximately 95%.When the three autoantibodies were combined,the sensitivity reached 30.4%and the specificity reached 91.6%.CONCLUSION Autoantibodies to NPM1,14-3-3zeta and MDM2 may be useful biomarkers for immunodiagnosis of AFP-negative HCC.展开更多
The development of low-cost,earth-abundant and environmentally benign transition metal catalysts,which can catalyze multiple different types of asymmetric reactions,is an important objective in mod-ern asymmetric cata...The development of low-cost,earth-abundant and environmentally benign transition metal catalysts,which can catalyze multiple different types of asymmetric reactions,is an important objective in mod-ern asymmetric catalysis.Herein we demonstrate that a chiral Ni/P-Phos catalyst achieves three types of asymmetric reactions:allenylic substitution of racemic allenic ethers,1,4-hydroalkylation of prochiral 1,3-enynes and double alkylation of newly designed enynyl ether reagents.Three methods complement each other and produce various axially chiral allene derivatives bearing a pyrazolidine-3,5-dione unit,which is widely present in drugs and biologically active molecules with versatile pharmacological activities.展开更多
The clinical treatment of DNA-repair defective tumours has been revolutionised by the use of poly(ADP)ribose polymerase(PARP)inhibitors.However,the efficacy of these compounds is hampered by resistance,which is attrib...The clinical treatment of DNA-repair defective tumours has been revolutionised by the use of poly(ADP)ribose polymerase(PARP)inhibitors.However,the efficacy of these compounds is hampered by resistance,which is attributed to numerous mechanisms including rewiring of the DNA damage response to favour pathways that repair PARP inhibitor-mediated damage.Here,we comment on recent findings by our group identifying the lysine methyltransferase SETD1A as a novel factor that conveys PARPi resistance.We discuss the implications,with a particular focus on epigenetic modifications and H3K4 methylation.We also deliberate on the mechanisms responsible,the consequences for the refinement of PARP inhibitor use in the clinic,and future possibilities to circumvent drug resistance in DNA-repair deficient cancers.展开更多
Three guests with two moiety probes for different Cucurbit[n = 6—8]urils have been synthesized. They are N-(2-methylenethiophen)-adamataneamine, N-(2-methylene pyrrole)- adamataneamine and N-(2-methylenefurfuran)-ada...Three guests with two moiety probes for different Cucurbit[n = 6—8]urils have been synthesized. They are N-(2-methylenethiophen)-adamataneamine, N-(2-methylene pyrrole)- adamataneamine and N-(2-methylenefurfuran)-adamataneamine. The probes are methyle-nepyridyl typically for Q[6] and adamataneamine typically for Q[7]. The host-guest complexes of Cucurbit[n = 6—8]urils with these guests have been investigated by using NMR techniques and ESMS method. Also, thermoanalysis has been used for exploring relationship of enthalpy and stability of the host-guest complexes.展开更多
To study the effect of Green plum citron double strain fermentation filtrate(DSF)on the proliferation rate of HaCaT keratinocytes by CCK8 assay.The effect of DSF on the mRNA transcription levels of filagolin(FLG),lori...To study the effect of Green plum citron double strain fermentation filtrate(DSF)on the proliferation rate of HaCaT keratinocytes by CCK8 assay.The effect of DSF on the mRNA transcription levels of filagolin(FLG),loricrin(LOR),and occludin 1(CLD1)in HaCaT cells in sodium dodecyl sulfate(SLS)model was investigated by qPCR.The effect of DSF on the content of TNF-αin the supernatant of HaCaT cells in the model was investigated by Elisa.The results showed that DSF had no toxicity to HaCaT cells,but it could increase the mRNA transcription levels of FLG,LOR and CLD1 in HaCaT cells in the model,and reduce the content of TNF-αin the supernatant of HaCaT cells in the model.DSF had a certain effect on skin care of strengthening skin barrier.展开更多
DNA double-strand breaks(DSBs)are involved in many cellular mechanisms,including replication,transcription,and genome rearrangements.The recent observation that hot spots of DSBs in human chromosomes delimit DNA domai...DNA double-strand breaks(DSBs)are involved in many cellular mechanisms,including replication,transcription,and genome rearrangements.The recent observation that hot spots of DSBs in human chromosomes delimit DNA domains that possess coordinately expressed genes suggests a strong relationship between the organization of transcription patterns and hot spots of DSBs.In this study,we performed mapping of hot spots of DSBs in a human 43-kb ribosomal DNA(rDNA)repeated unit.We observed that rDNA units corresponded to the most fragile sites in human chromosomes and that these units possessed at least nine specific regions containing clusters of extremely frequently occurring DSBs,which were located exclusively in non-coding intergenic spacer(IGS)regions.The hot spots of DSBs corresponded to only a specific subset of DNase-hypersensitive sites,and coincided with CTCF,PARP1,and HNRNPA2B1 binding sites,and H3K4me3 marks.Our rDNA-4C data indicate that the regions of IGS containing the hot spots of DSBs often form contacts with specific regions in different chromosomes,including the pericentromeric regions,as well as regions that are characterized by H3K27ac and H3K4me3 marks,CTCF binding sites,ChIA-PET and RIP signals,and high levels of DSBs.The data suggest a strong link between chromosome breakage and several different mechanisms of epigenetic regulation of gene expression.展开更多
T lymphocytes bearing the ab T cell receptor(TCR)but lacking CD4,CD8,and markers of natural killer(NK)cell differentiation are known as‘double-negative’(DN)T cells and have been described in both humans and rodent m...T lymphocytes bearing the ab T cell receptor(TCR)but lacking CD4,CD8,and markers of natural killer(NK)cell differentiation are known as‘double-negative’(DN)T cells and have been described in both humans and rodent models.We and others have shown that DN T cells can act as regulatory T cells(Tregs)that are able to prevent allograft rejection,graft-versus-host disease,and autoimmune diabetes.In the last few years,new data have revealed evidence of DN Treg function in vivo in rodents and humans.Moreover,significant advances have been made in the mechanisms by which DN Tregs target antigen-specific T cells.One major limitation of the field is the lack of a specific marker that can be used to distinguish truly regulatory DN T cells(DN Tregs)from non-regulatory ones,and this is the central challenge in the coming years.Here,we review recent progress on the role of DN Tregs in transplantation and autoimmunity,and their mechanisms of action.We also provide some perspectives on how DN Tregs compare with Foxp31 Tregs.展开更多
A flexible double betaine 1,4-bis（pyridinil-4-carboxylato）-1,4-dimethylbenzene L has been used to generate two Cu（Ⅱ）-containing metal complexes that exhibit different polymeric structures： [Cu（H2O）2 L].2NO3 1 ...A flexible double betaine 1,4-bis（pyridinil-4-carboxylato）-1,4-dimethylbenzene L has been used to generate two Cu（Ⅱ）-containing metal complexes that exhibit different polymeric structures： [Cu（H2O）2 L].2NO3 1 and [Cu（H2O）3 L].2Cl.H2O 2. The crystal structures of 1 and 2 have been determined by single-crystal X-ray diffraction method. Crystal data for 1： triclinic, space group PT, a = 5.253（2）, b = 7.406（3）, c = 14.792（5） A, α = 84.195（5）, β = 80.014（5）, γ = 78.053（5）°, V= 553.2（3）A^3, Z = 1, F（000） = 293, Dc = 1.717 g/cm^3, the final R = 0.0385 and wR = 0.1079 for 1883 observed reflections （I 〉 2σ（I））; and those for 2： monoclinic, space group P21/c, a = 10.222（3）, b = 25.287（7）, c = 9.277（3）A, β = 93.572（5）°, V = 2393.2（12）A^3, Z = 4, F（000） = 1140, Dc = 1.540 g/cm^3, the final R = 0.0472 and wR = 0.0956 for 3204 observed reflections （I 〉2o（/））.展开更多
Using the optical-optical double resonance （OODR） technique, we have studied the collisional broadening of some 21△g←B1πu lines in Na2 molecules. A single line Ar＋ laser is used to pump the sodium dimers from t...Using the optical-optical double resonance （OODR） technique, we have studied the collisional broadening of some 21△g←B1πu lines in Na2 molecules. A single line Ar＋ laser is used to pump the sodium dimers from thermally populated ground state X^1∑^＋g level to the intermediate B1πu state. Then, a single-mode diode laser is used to probe the doubly excited 21△g state. The broadening rate coefficient is determined from the slope of the total linewidth versus Ne density curve. We obtain the average value kbr = （1.1 ± 0.5）×10^-8 cm^3 8^-1. The collisional excitation transfer between rotational levels of the B1πu state （i.e.,B1πu（2,83/84） ←B1Ⅱu （2,82）） is also investigated. The rates can be determined from the relative intensities of the main peak and satellite lines, combined with a rate equation model. The rates of 1.25 × 106 and 1.07 × 106 s^-1 are obtained, respectively.展开更多
The calcined Mg-A1 layered double hydroxides （LDHs） with a Mg/A1 molar ratio of 3 ： 1 were synthesized and characterized thoroughly by X-ray diffraction （XRD）, temperature-programmed desorption （TPD） of CO2, an...The calcined Mg-A1 layered double hydroxides （LDHs） with a Mg/A1 molar ratio of 3 ： 1 were synthesized and characterized thoroughly by X-ray diffraction （XRD）, temperature-programmed desorption （TPD） of CO2, and thermogravimetric analysis （TGA）. Thus the calcined Mg-A1 LDHs were used as catalyst for the catalytic synthesis of disubstituted ureas from amines and CO2. The effects of reaction time, reaction temperature, pressure, solvent and calcined temperature on activity have been investigated. The results indicated that aliphatic amines, cyclo- hexylamine and benzylamine can be converted to the corresponding ureas selectively over the calcined Mg-A1 LDHs catalysts with N-methyl-2-pyrrolidone （NMP） as solvent without using any dehydrating regent. The catalyst can be recycled several times with only slight loss of activity.展开更多
Excited-state double proton transfer(ESDPT)is a controversial issue which has long been plagued with theoretical and experimental communities.Herein,we took 1,8-dihydroxy-2-naphthaldehyde(DHNA)as a prototype and used ...Excited-state double proton transfer(ESDPT)is a controversial issue which has long been plagued with theoretical and experimental communities.Herein,we took 1,8-dihydroxy-2-naphthaldehyde(DHNA)as a prototype and used combined complete active space selfconsistent field(CASSCF)and multi-state complete active-space second-order perturbation(MS-CASPT2)methods to investigate ESDPT and excited-state deactivation pathways of DHNA.Three different tautomer minima of S1-ENOL,S1-KETO-1,and S1-KETO-2 and two crucial conical intersections of S1 S0-KETO-1 and S1 S0-KETO-2 in and between the S0 and S1 states were obtained.S1-KETO-1 and S1-KETO-2 should take responsibility for experimentally observing dual-emission bands.In addition,two-dimensional potential energy surfaces(2 D-PESs)and linear interpolated internal coordinate paths connecting relevant structures were calculated at the MS-CASPT2//CASSCF level and confirmed a stepwise ESDPT mechanism.Specifically,the first proton transfer from S1-ENOL to S1-KETO-1 is barrierless,whereas the second one from S1-KETO-1 to S1-KETO-2 demands a barrier of ca.6.0 kcal/mol.The linear interpolated internal coordinate path connecting S1-KETO-1(S1-KETO-2)and S_(1) S0-KETO-1(S1 S0-KETO-2)is uphill with a barrier of ca.12.0 kcal/mol,which will trap DHNA in the S_(1) state while therefore enabling dual-emission bands.On the other hand,the S1/S0 conical intersections would also prompt the S_(1) system to decay to the S_(0) state,which could be to certain extent suppressed by locking the rotation of the C5-C8-C9-O10 dihedral angle.These mechanistic insights are not only helpful for understanding ESDPT but also useful for designing novel molecular materials with excellent photoluminescent performances.展开更多
Carbon capture and storage technology have been rapidly developed to reduce the carbon dioxide(CO2)emission into the environment.It has been found that the amine-based organic molecules could absorb CO_(2) efficiently...Carbon capture and storage technology have been rapidly developed to reduce the carbon dioxide(CO2)emission into the environment.It has been found that the amine-based organic molecules could absorb CO_(2) efficiently and form the bicarbonate salts through hydrogen-bond(H-bond)interactions.Recently,the aqueous 1,3-diphenylguanidine(DPG)solution was developed to trap and convert CO_(2) to valuable chemicals under ambient conditions.However,how the DPG molecules interact with CO_(2) in an aqueous solution remains unclear.In this work,we perform molecular dynamics simulations to explore the atomistic details of CO_(2) in the aqueous DPG.The simulated results reveal that the protonated DPGH+and the bicarbonate anions prefer to form complexes through different H-bond patterns.These double H-bonds are quite stable in thermodynamics,as indicated from the accurate density functional theory calculations.This study is helpful to understand the catalytic mechanism of CO_(2) conversion in the aqueous DPG.展开更多
Meiotic prophase I is a long and complex phase. Homologous recombination is an important process that occurs between homologous chromosomes during meiotic prophase I. Formation of chiasmata, which hold homologous chro...Meiotic prophase I is a long and complex phase. Homologous recombination is an important process that occurs between homologous chromosomes during meiotic prophase I. Formation of chiasmata, which hold homologous chromosomes together until the metaphase I to anaphase I transition, is critical for proper chromosome segregation. Recent studies have suggested that the SPO 11 proteins have conserved functions in a number of organisms in generating sites of double-stranded DNA breaks （DSBs） that are thought to be the starting points of homologous recombination. Processing of these sites of DSBs requires the function of RecA homologs, such as RAD5 1, DMC 1, and others, as suggested by mutant studies; thus the failure to repair these meiotic DSBs results in abnormal chromosomal alternations, leading to disrupted meiosis. Recent discoveries on the functions of these RecA homologs have improved the understanding of the mechanisms underlying meiotic homologous recombination.展开更多
文摘The genomes of eukaryotic cells are under continuous assault by environmental agents and endogenous metabolic byproducts. Damage induced in DNA usually leads to a cascade of cellular events, the DNA damage response. Failure of the DNA damage response can lead to development of malignancy by reducing the efficiency and fidelity of DNA repair. The NBS1 protein is a component of the MRE11/RAD50/NBS 1 complex （MRN） that plays a critical role in the cellular response to DNA damage and the maintenance of chromosomal integrity. Mutations in the NBS1 gene are responsible for Nijmegen breakage syndrome （NBS）, a hereditary disorder that imparts an increased predisposition to development of malignancy. The phenotypic characteristics of cells isolated from NBS patients point to a deficiency in the repair of DNA double strand breaks. Here, we review the current knowledge of the role of NBS1 in the DNA damage response. Emphasis is placed on the role of NBS1 in the DNA double strand repair, modulation of the DNA damage sensing and signaling, cell cycle checkpoint control and maintenance oftelomere stability.
基金Supported by Clinical Research Cooperation Fund of the Capital Medical University,No.15JL67Project of Science and Technology Development Plan of Beijing Municipal Education Commission,No.KM201610025021+2 种基金High-Tech Personnel Training Program of Beijing Health System,No.2015-3-104Beijing Municipal Science and Technology Commission,No.Z151100004015066Shaanxi Science and Technology Coordination and Innovation Project,No.2016KTZDSF02-02
文摘AIM To determine the prevalence and diagnostic value of autoantibodies inα-fetoprotein(AFP)-negative hepatocellular carcinoma(HCC).METHODS Fifty-six serum samples from AFP-negative HCC cases,86 from AFP-positive HCC cases,168 from chronic liver disease cases,and 59 from normal human controls were included in this study.Autoantibodies to nucleophosmin(NPM)1,14-3-3zeta and mouse double minute 2 homolog(MDM2)proteins in AFP-negative HCC serum were evaluated by enzymelinked im munosorbent assay.Partially positive sera were further evaluated by western blotting.Immunohistochemistry was used to detect the expression of three tumor-associated antigens(TAAs)in AFP-negative HCC and normal control tissues.RESULTS The frequency of autoantibodies to the three TAAs in AFP-negative HCC sera was 21.4%,19.6%and 19.6%,which was significantly higher than in the chronic liver disease cases and normal human controls(P<0.01)as well as AFP-positive HCC cases.The sensitivity of the three autoantibodies for diagnosis of AFP-negative HCC ranged from 19.6%to 21.4%,and the specificity was approximately 95%.When the three autoantibodies were combined,the sensitivity reached 30.4%and the specificity reached 91.6%.CONCLUSION Autoantibodies to NPM1,14-3-3zeta and MDM2 may be useful biomarkers for immunodiagnosis of AFP-negative HCC.
基金supported by the National Natural Science Foundation of China (No.22171240)
文摘The development of low-cost,earth-abundant and environmentally benign transition metal catalysts,which can catalyze multiple different types of asymmetric reactions,is an important objective in mod-ern asymmetric catalysis.Herein we demonstrate that a chiral Ni/P-Phos catalyst achieves three types of asymmetric reactions:allenylic substitution of racemic allenic ethers,1,4-hydroalkylation of prochiral 1,3-enynes and double alkylation of newly designed enynyl ether reagents.Three methods complement each other and produce various axially chiral allene derivatives bearing a pyrazolidine-3,5-dione unit,which is widely present in drugs and biologically active molecules with versatile pharmacological activities.
基金supported by a PhD studentship from the University of Birmingham and Cancer Research UK(C17422/A25154)awarded to Sweatman E and Higgs MRa Breast Cancer Now project grant(2019AugPR1320)supporting Bayley R(awarded to Garcia P)an MRC Career Development Fellowship(MR/P009085/1)awarded to Higgs MR.
文摘The clinical treatment of DNA-repair defective tumours has been revolutionised by the use of poly(ADP)ribose polymerase(PARP)inhibitors.However,the efficacy of these compounds is hampered by resistance,which is attributed to numerous mechanisms including rewiring of the DNA damage response to favour pathways that repair PARP inhibitor-mediated damage.Here,we comment on recent findings by our group identifying the lysine methyltransferase SETD1A as a novel factor that conveys PARPi resistance.We discuss the implications,with a particular focus on epigenetic modifications and H3K4 methylation.We also deliberate on the mechanisms responsible,the consequences for the refinement of PARP inhibitor use in the clinic,and future possibilities to circumvent drug resistance in DNA-repair deficient cancers.
文摘Three guests with two moiety probes for different Cucurbit[n = 6—8]urils have been synthesized. They are N-(2-methylenethiophen)-adamataneamine, N-(2-methylene pyrrole)- adamataneamine and N-(2-methylenefurfuran)-adamataneamine. The probes are methyle-nepyridyl typically for Q[6] and adamataneamine typically for Q[7]. The host-guest complexes of Cucurbit[n = 6—8]urils with these guests have been investigated by using NMR techniques and ESMS method. Also, thermoanalysis has been used for exploring relationship of enthalpy and stability of the host-guest complexes.
文摘To study the effect of Green plum citron double strain fermentation filtrate(DSF)on the proliferation rate of HaCaT keratinocytes by CCK8 assay.The effect of DSF on the mRNA transcription levels of filagolin(FLG),loricrin(LOR),and occludin 1(CLD1)in HaCaT cells in sodium dodecyl sulfate(SLS)model was investigated by qPCR.The effect of DSF on the content of TNF-αin the supernatant of HaCaT cells in the model was investigated by Elisa.The results showed that DSF had no toxicity to HaCaT cells,but it could increase the mRNA transcription levels of FLG,LOR and CLD1 in HaCaT cells in the model,and reduce the content of TNF-αin the supernatant of HaCaT cells in the model.DSF had a certain effect on skin care of strengthening skin barrier.
基金supported bya grant from the Molecular and Cellular Biology Program of the Russian Academy of Sciences and by grantsfrom the Russian Foundation for Basic Research(#12-04-01416-a,#12-04-01311-a,#14-04-01638-a,and#15-04-00299-a)by a President Grant for Government Support of Young Russian Scientists MK-1934.2014.4.
文摘DNA double-strand breaks(DSBs)are involved in many cellular mechanisms,including replication,transcription,and genome rearrangements.The recent observation that hot spots of DSBs in human chromosomes delimit DNA domains that possess coordinately expressed genes suggests a strong relationship between the organization of transcription patterns and hot spots of DSBs.In this study,we performed mapping of hot spots of DSBs in a human 43-kb ribosomal DNA(rDNA)repeated unit.We observed that rDNA units corresponded to the most fragile sites in human chromosomes and that these units possessed at least nine specific regions containing clusters of extremely frequently occurring DSBs,which were located exclusively in non-coding intergenic spacer(IGS)regions.The hot spots of DSBs corresponded to only a specific subset of DNase-hypersensitive sites,and coincided with CTCF,PARP1,and HNRNPA2B1 binding sites,and H3K4me3 marks.Our rDNA-4C data indicate that the regions of IGS containing the hot spots of DSBs often form contacts with specific regions in different chromosomes,including the pericentromeric regions,as well as regions that are characterized by H3K27ac and H3K4me3 marks,CTCF binding sites,ChIA-PET and RIP signals,and high levels of DSBs.The data suggest a strong link between chromosome breakage and several different mechanisms of epigenetic regulation of gene expression.
基金Research in our laboratory has been supported by Canadian Institutes of Health Research Grant (#14431)Canadian Cancer Society to L.Z.S.C.J.received salary support from a Terry Fox Foundation/National Cancer Institute of Canada Clinical Research Fellowship (#18014)the Clinician-Scientist Training Program,Department of Medicine,University of Toronto.
文摘T lymphocytes bearing the ab T cell receptor(TCR)but lacking CD4,CD8,and markers of natural killer(NK)cell differentiation are known as‘double-negative’(DN)T cells and have been described in both humans and rodent models.We and others have shown that DN T cells can act as regulatory T cells(Tregs)that are able to prevent allograft rejection,graft-versus-host disease,and autoimmune diabetes.In the last few years,new data have revealed evidence of DN Treg function in vivo in rodents and humans.Moreover,significant advances have been made in the mechanisms by which DN Tregs target antigen-specific T cells.One major limitation of the field is the lack of a specific marker that can be used to distinguish truly regulatory DN T cells(DN Tregs)from non-regulatory ones,and this is the central challenge in the coming years.Here,we review recent progress on the role of DN Tregs in transplantation and autoimmunity,and their mechanisms of action.We also provide some perspectives on how DN Tregs compare with Foxp31 Tregs.
基金This work was financially supported by Liuhui Center for Applied Mathematics, Nankai and Tianjin Universities (No. H10114)
文摘A flexible double betaine 1,4-bis（pyridinil-4-carboxylato）-1,4-dimethylbenzene L has been used to generate two Cu（Ⅱ）-containing metal complexes that exhibit different polymeric structures： [Cu（H2O）2 L].2NO3 1 and [Cu（H2O）3 L].2Cl.H2O 2. The crystal structures of 1 and 2 have been determined by single-crystal X-ray diffraction method. Crystal data for 1： triclinic, space group PT, a = 5.253（2）, b = 7.406（3）, c = 14.792（5） A, α = 84.195（5）, β = 80.014（5）, γ = 78.053（5）°, V= 553.2（3）A^3, Z = 1, F（000） = 293, Dc = 1.717 g/cm^3, the final R = 0.0385 and wR = 0.1079 for 1883 observed reflections （I 〉 2σ（I））; and those for 2： monoclinic, space group P21/c, a = 10.222（3）, b = 25.287（7）, c = 9.277（3）A, β = 93.572（5）°, V = 2393.2（12）A^3, Z = 4, F（000） = 1140, Dc = 1.540 g/cm^3, the final R = 0.0472 and wR = 0.0956 for 3204 observed reflections （I 〉2o（/））.
基金This work was supported by the National Natural Science Foundation of China under Grant No. 10264004.
文摘Using the optical-optical double resonance （OODR） technique, we have studied the collisional broadening of some 21△g←B1πu lines in Na2 molecules. A single line Ar＋ laser is used to pump the sodium dimers from thermally populated ground state X^1∑^＋g level to the intermediate B1πu state. Then, a single-mode diode laser is used to probe the doubly excited 21△g state. The broadening rate coefficient is determined from the slope of the total linewidth versus Ne density curve. We obtain the average value kbr = （1.1 ± 0.5）×10^-8 cm^3 8^-1. The collisional excitation transfer between rotational levels of the B1πu state （i.e.,B1πu（2,83/84） ←B1Ⅱu （2,82）） is also investigated. The rates can be determined from the relative intensities of the main peak and satellite lines, combined with a rate equation model. The rates of 1.25 × 106 and 1.07 × 106 s^-1 are obtained, respectively.
基金The authors are grateful for the support from the Na-tional Natural Science Foundation of China （No. 21073058）, the Research Fund for the Doctoral Program of Higher Education of China （20100074110014）, and the Fundamental Research Funds for the Central Uni-versities.
文摘The calcined Mg-A1 layered double hydroxides （LDHs） with a Mg/A1 molar ratio of 3 ： 1 were synthesized and characterized thoroughly by X-ray diffraction （XRD）, temperature-programmed desorption （TPD） of CO2, and thermogravimetric analysis （TGA）. Thus the calcined Mg-A1 LDHs were used as catalyst for the catalytic synthesis of disubstituted ureas from amines and CO2. The effects of reaction time, reaction temperature, pressure, solvent and calcined temperature on activity have been investigated. The results indicated that aliphatic amines, cyclo- hexylamine and benzylamine can be converted to the corresponding ureas selectively over the calcined Mg-A1 LDHs catalysts with N-methyl-2-pyrrolidone （NMP） as solvent without using any dehydrating regent. The catalyst can be recycled several times with only slight loss of activity.
基金supported by the National Key Research and Development Program of China for BinBin Xie(No.2019YFA0709400)the National Natural Science Foundation of China for Bin-Bin Xie(No.21903068)+1 种基金Xiang-Yang Liu(No.22003043)Natural Science Foundation of Zhejiang Province for Bin-Bin Xie(No.LQ19B030007)。
文摘Excited-state double proton transfer(ESDPT)is a controversial issue which has long been plagued with theoretical and experimental communities.Herein,we took 1,8-dihydroxy-2-naphthaldehyde(DHNA)as a prototype and used combined complete active space selfconsistent field(CASSCF)and multi-state complete active-space second-order perturbation(MS-CASPT2)methods to investigate ESDPT and excited-state deactivation pathways of DHNA.Three different tautomer minima of S1-ENOL,S1-KETO-1,and S1-KETO-2 and two crucial conical intersections of S1 S0-KETO-1 and S1 S0-KETO-2 in and between the S0 and S1 states were obtained.S1-KETO-1 and S1-KETO-2 should take responsibility for experimentally observing dual-emission bands.In addition,two-dimensional potential energy surfaces(2 D-PESs)and linear interpolated internal coordinate paths connecting relevant structures were calculated at the MS-CASPT2//CASSCF level and confirmed a stepwise ESDPT mechanism.Specifically,the first proton transfer from S1-ENOL to S1-KETO-1 is barrierless,whereas the second one from S1-KETO-1 to S1-KETO-2 demands a barrier of ca.6.0 kcal/mol.The linear interpolated internal coordinate path connecting S1-KETO-1(S1-KETO-2)and S_(1) S0-KETO-1(S1 S0-KETO-2)is uphill with a barrier of ca.12.0 kcal/mol,which will trap DHNA in the S_(1) state while therefore enabling dual-emission bands.On the other hand,the S1/S0 conical intersections would also prompt the S_(1) system to decay to the S_(0) state,which could be to certain extent suppressed by locking the rotation of the C5-C8-C9-O10 dihedral angle.These mechanistic insights are not only helpful for understanding ESDPT but also useful for designing novel molecular materials with excellent photoluminescent performances.
基金supported by the National Natural Science Foundation of China(No.21973015 and No.22125301)。
文摘Carbon capture and storage technology have been rapidly developed to reduce the carbon dioxide(CO2)emission into the environment.It has been found that the amine-based organic molecules could absorb CO_(2) efficiently and form the bicarbonate salts through hydrogen-bond(H-bond)interactions.Recently,the aqueous 1,3-diphenylguanidine(DPG)solution was developed to trap and convert CO_(2) to valuable chemicals under ambient conditions.However,how the DPG molecules interact with CO_(2) in an aqueous solution remains unclear.In this work,we perform molecular dynamics simulations to explore the atomistic details of CO_(2) in the aqueous DPG.The simulated results reveal that the protonated DPGH+and the bicarbonate anions prefer to form complexes through different H-bond patterns.These double H-bonds are quite stable in thermodynamics,as indicated from the accurate density functional theory calculations.This study is helpful to understand the catalytic mechanism of CO_(2) conversion in the aqueous DPG.
基金The authors thank Alexandra Surcel and Carey L Hendrix Lord for helpful comments on this manuscript.The work in our laboratory is supported by grants from the National Science Foundation(IBN-0077832,MCB-9896340,MCB-0092075)the National Institutes of Health(R0 1 GM63871)+3 种基金the US Department of Agriculture(2001-35301-10570 and 2003-35301-13313)Wuxing L was partially supported by the Intercollege Graduate Degree Program in Plant PhysiologyHong M gratefully acknowledges the support of the John Simon Guggenheim Foundationthe National Institutes of Health(F33 GM72245-1).
文摘Meiotic prophase I is a long and complex phase. Homologous recombination is an important process that occurs between homologous chromosomes during meiotic prophase I. Formation of chiasmata, which hold homologous chromosomes together until the metaphase I to anaphase I transition, is critical for proper chromosome segregation. Recent studies have suggested that the SPO 11 proteins have conserved functions in a number of organisms in generating sites of double-stranded DNA breaks （DSBs） that are thought to be the starting points of homologous recombination. Processing of these sites of DSBs requires the function of RecA homologs, such as RAD5 1, DMC 1, and others, as suggested by mutant studies; thus the failure to repair these meiotic DSBs results in abnormal chromosomal alternations, leading to disrupted meiosis. Recent discoveries on the functions of these RecA homologs have improved the understanding of the mechanisms underlying meiotic homologous recombination.
