简介:采用密度泛函理论(DFT)对P450酶活性中心铁卟啉CpdI催化二乙基亚硝胺(NDEA)代谢活化的反应机理进行了研究.结果表明,CpdI催化NDEA羟基化的过程包含氢抽提反应和回弹反应2个步骤.其中,氢抽提反应为控速步骤,氢自由基从NDEA转移到铁卟啉的FeO上,是典型的氢原子传递(HAT)过程;紧接着铁卟啉上的羟基经历无能垒的反应过程回弹到NDEA自由基上,形成羟基化代谢产物.NDEA羟基化过程中高自旋态(HS)和低自旋态(LS)均参与反应,整个羟基化过程呈现明显的双态反应性(TSR).研究比较了NDEA分子侧链上C^αH和C^βH羟基化反应的差异,得到C^αH和C^βH羟基化所需跨越的能垒分别为57.7/57.7kJ/mol(LS/HS)和76.4/74.3kJ/mol(LS/HS),表明C^αH比C^βH更易于在P450作用下发生羟基化;此外,C^βH羟基化所需克服的能垒并未过高,使得C^βH羟基化在生理条件下完全也有可能发生.本研究为深入揭示亚硝胺经代谢活化导致癌症的作用机制提供了可靠的理论依据.
简介:Thecrystalandmolecularstructuresof[(C3H7O)2PS2]2(CCDCNo.217201)weredeterminedbymeansofX-raycrystallography.ItcrystallizedinatriclinicsystemwithspacegroupP1^-andlatticeparametersa=0.82794(3)nm,b=0.84764(2)nm,c=0.85034(3)nm,α=97.78(3)°β=110.77(3)°,γ=94.95(3)°,V=0.54701(9)nm^3,Z=1.Inthismolecule,thetwodiisopropyldithiophosphategroups,[(C3H7O)2PS2]2,whichareparalleltoeachother,arelinkedbyanS--Sbondandthereexistinversioncentersinthemolecule,Inthestructure,theP=Sbondsinthetwodithiophosphateunitsaretrans-orientedtoeachother.
简介:研究了YBaCu3O6~7超导催化剂上CO2的加氢制醇反应。考察了温度、压力和空速等条件对催化剂反应性能的影响。反应的主要产物是甲醇、CO和少量甲醚。利用XPS、XRD和AFM等技术对催化剂的结构、铜的存在状态和反应活性位进行表征发现,在反应过程中,YBa2Cu3O6~7由orthombic相转变为tetragonal相。反应活性位可能是Cu(I)物种。反应后催化剂颗粒的分散程度明显提高
简介:Lifetimemeasurementsoflow-lyingexcitedstatesin^87Zrhavebeenperformedviaβ-γcoincidences.The127MeV^32SbeamwasdeliveredfromtheSector-FocusingCyclotron(SFC)oftheHeavyIonResearchFacilityinLanzhou(HIRFL).Theparentnuclei^87Nbwereproducedbythereaction58Ni(32S,2p1n),atabeamenergy127MeVthrougha8umAldegrader.A200ug/cm^2layerof58Nievaporatedontoa200ug/cm^2thickcarbonfoilwasemployedasthetarget.Afterevaporationresidueswereseparatedfromtheprojectilebeamsbythegas-filledrecoilseparatorSHANS[1],thenucleiofinterest87Zrcanbeobtainedwithahigherpurityandthenwereimplantedintoa300umsilicondetector.
简介:TheapplicationofLanthanumBromide(LaBr3)detectorsprovidesauniqueopportunitytomeasurelifetimeofexcitedstatesinpicosecond-nanosecondregion.Reducingthebackgroundisofcriticalimportancetogetpreciseresults.Forsomeexcitedstatesfeedingfromisomerswithlifetimelongerthan1μs,itcanbeachievedbytheSpectrometerforHeavyAtomandNuclearStructure(SHANS)[1].143Eunucleiwerepopulatedviathe123Sb(24Mg,4n)fusion-evaporationreaction.Mostoftheevaporationresiduesatgroundstateorlong-livedisomersweretransferredtodetectionterminalafteraflightofabout1.4μsinSHANS.Inthecaseof143Eu,threetransitionshavebeenobserved(Fig.1).
简介:Atacertainhightemperature,thiscyclewillbedominantandendtherp-processtoheavierregion[2].Itprovidesanuppertemperaturelimitforrp-processalongtheprotondriplinetoproducenuclidesbeyondA=84,includingthelightpnuclidesof92;94Mo,96;94Ru.TheexistenceofZr-Nbcycleisanimportantquestioninrp-process[2].α-separationenergy(Sα)of84Moplaysanimportantroleintheformationofthiscycle.Astrongenhancementof83Nb(p,α)reactionrateisduetoaverylowSαof84Mo[1].
简介:标题化合物C26H26O5以2,3-萘二甲醛和5-甲基-1,3-环己二酮为原料,在醋酸溶剂中,室温下经搅拌多组分一锅法合成得到.其结构通过单晶X-射线衍射法确定,晶体属单斜晶系,空间群P21,相对分子质量Mr=418.47,晶胞参数a=0.99004(8)nm,b=1.09098(9)nm,c=1.04246(11)nm,V=1.08753(17)nm3,Z=2,晶胞密度Dc=1.278g/cm3,吸收系数μ=0.088mm-1,单胞中电子的数目F(000)=444.晶体结构用直接法解出,经全矩阵最小二乘法对原子参数进行修正,最终的偏离因子为R1=0.0533,wR2=0.1293.在晶体结构中新形成的吡喃环为半椅式构象,而茚中五元环则为信封式构象.
简介:Theneworganic-inorganiccompound,[C_6H_7N_2O_2]_3TeCl_5·2Clwassynthesizedanditsstructurewasdeterminedatroomtemperatureinthetriclinicsystem(P~-1)withthefollowingparameters:a=10.5330(11)?,b=10.6663(11)?,c=15.9751(16)?,α=82.090(2)°,β=71.193(2)°,γ=68.284(2)°andZ=2.ThefinalcycleofrefinementledtoR=0.057andRw=0.149.ThecrystalstructurewasstabilizedbyanextensivenetworkofN--H···Clandnon-classicalC--H···Clhydrogenbondsbetweenthecationandtheanionicgroup.Severalthermalanalysistechniquessuchasthermogravimetricanalysis,differentialscanningcalorimetricanalysisandevolvedgasanalysiswereused.Weusedisoconversionalkineticsmethodstodeterminethekineticsparameters.Weobservethatthedecompositionof[C_6H_7N_2O_2]_3TeCl_5·2Clentailstheformationhydrochloricacidofnitroanilineasvolatiles.Theinfraredspectrawererecordedinthe4000–400cm~(-1)frequencyregion.TheRamanspectrawererecordedintheexternalregionoftheanionicsublatticevibration50–1500cm~(-1).TheopticalbandgapwascalculatedfromtheUV-VisabsorbancespectrausingclassicalTaucrelationwhichwasfoundtobe3.12and3.67eV.
简介:Fourkeyreactions,12C(,)13O,13C(,n)16O,25Mg(p,)26Aland19F(p,)16O,willbestudiedforthefirsttimewithinorneartheastrophysicalrelevantenergyregions(Gamowwindow)atJinpingUndergroundlaboratoryforNuclearAstrophysics(JUNA)[1],whichwilltaketheadvantageoftheultra-lowbackgroundofChinaJinPingundergroundLaboratory(CJPL),highcurrentacceleratorbasedonECRsourceandahighlysensitivedetectionsystem.
简介:Thispaperreportstwolanthanidecomplexesofformula(C9H7)Ln(C8H8)·(THF)2whereLnisProrNd,C9H7isindenyl,andC8H8iscyclooctatetraene(COT).ThecomplexeswerepreparedbythereactionofLnCl3withK(C9H7)andK2(C8H8)inTHF.(C9H7)Pr(C8H8)·(THF)2crystallizesinTHFat-15℃inthemonoclinicspacegroupP21:withunitcelldimensionsa=8.446(0),b=10.083(2),c=13.407(3),β=105.48(1)°,V=1100.43(35)3,Dc=1.52g/cm3andZ=2.ThefinalRvalueis0.033,Rwvalueis0.030,respectively.In(C9H7)Pr(C8H8)·(THF)2afive-memberedringcentroidofC9H7,theC8H8ringcentroidandthetwooxygenatomsfromthetwoTHFmoleculesformadistortedtetrahedralgeometryaroundthemetal.
简介:8,8′-Dibromo-6,6′,7,7′-tetramethoxy-5,5′-diisopropyl-3,3′-oxydimethylenedinaphtho[2,1-b:2′,1′-d]furan,C32H30Br2O;M.W.=670;triclinic;spacegroupP1;a=8.896(2),b=10.216(1),c=10.423(1)A,α=108.48(1),β=119.36(1),γ=99.26(1);V=723.5A3;Z=1,Dcal.=1.479g.cm-3.MoKα=28.11cm-1,F(000)=326,T=293K.Thestructurewassolvedbydirectmethodandfull-matrixleast-squaresrefinementconvergedatR=0.034for2377observedreflections.Theoxygenatominseven-memberedringexistsinadisorderedarrangement.Bothbisnaphthaleneandoxygen-containingfive-memberedringhaveplanarconformationswithdihedralangle6°,showingmarkedaromaticfeature.
简介:合成了通式为K10H5[Ln(PMo7W2VO39)2].nH2O(Ln-La^3+,Ce^3+,Pr^3+,Nd^3+,Sm^3+,Eu^3+,Gd^3+,Dy^3+,Yb^3)的9种五元新型杂多配合物,并用元素化学分析,TG,ICP,IR,UV,31^1P,51V-NMR,ESR,XPS,XRD进行了表征,结果表明新配合物仍保持Keggin结构,稀土元素处于配合物的内界。借助TG-DTA,不同温度下的IR,XRD的水溶性实验考察了新配合物的热解性质,得出了热稳定的温度范围为400℃-500℃,为催化研究提供了依据。
简介:Kineticsofchloride/sulfate,chloride/nitrateandnitrate/sulfateforwardexchangesandreverseexchangesatsolutionconcentrationsof1N,0.2Nand0.02Non201×7strongbaseanionexchangeresin,respectively,havebeenexaminedat25℃.Itisfoundthattheforwardandthereverseexchangeratesofthetwogivenionsatlowsolutionconcentration,respectively,underidenticalconditionscanbecontrolledbydifferentmechanisms,whilethoseathighsolutionconcentrationareallcontrolledbyparticlediffusion.Theternaryexchangeratesofsulfate/(chloride+nitrate)andnitrate/(chloride+sulfate)havealsobeenexamined.
简介:InsituhighpressureenergydispersiveX-raydiffractionmeasurementsonlayeredperovskite-likemanganateCa3Mn2O7underpressuresupto35GPahavebeenPerformedbyusingdiamondanvilcellwithsynchrotronradiation.Theresultsshowthatthestructureoflayeredperovskite-likemanganateCa3Mn2O7isunstableunderpressureduetotheeasycompressionofNaCl-typeblocks.ThestructureofCa3Mn2O7underwenttwophasetransitionsunderpressuresintherangeof0-35GPa.Onewasatabout1.3GPawiththecrystalstructurechangingfromtetragonaltgoorthorhombic.Theotherwasatabout9.5GPawiththecrystalstructurechangingformorthorhombicbacktoanothertetragonal.
简介:Anewapproachtodeterminealltheelectro-elasticconstantsofthepiezoelectriccrystalsinclass4mmhasbeenputforward.Asanexample,alltheconstantsofLithiumTetraborate(Li2B4O7)crystalhavebeenmeasuredbymeansoftheapproach.Theoutstandingadvantageoftheapproachisthatiton-lyneedstoemployinmeasurementthreecrystalplatesdifferentlyoriented.