简介:At-hyperwheel(t≥3)oflengthl(orW(t)lforbrevity)isat-uniformhypergraph(V,E),whereE={e1,e2,...,el}andv1,v2,...,vlaredistinctverticesofV=∪eii=1lsuchthatfori=1,...,l,vi,vi+1∈eiandei∩ej=P,j∈/{i1,i,i+1},wheretheoperationonthesubscriptsismodulolandPisavertexofVwhichisdifferentfromvi,1≤i≤l.Inthispaper,theminimumcoveringproblemofMCλ(3,W(3)4,v)isinvestigated.DirectandrecursiveconstructionsonMCλ(3,W(3)4,v)arepresented.Thecoveringnumbercλ(3,W(3)4,v)isfinallydeterminedforanypositiveintegersv≥5andλ.
简介:DrugsSPD-304(6,7-dimethyl-3-{[methyl-(2-{methyl-[1-(3-trifluoromethyl-phenyl)-1H-indol-3-ylmethyl]-amino}-ethyl)-amino]-methyl}-chromen-4-one)andzafirlukastcontainacommonstructuralelementof3-substitutedindolemoietywhichcloselyrelatestoadehydrogenatedreactioncatalyzedbycytochromeP450s(CYPs).ItwasreportedthatthedehydrogenationcanproduceareactiveelectrophilicintermediatewhichcausetoxicitiesandinactivateCYPs.DrugL-745,870(3-{[4-(4-chlorophenyl)piperazin-1-yl]-methyl}-1H-pyrrolo2,3-β-pyridine)mighthavesimilareffectsinceitcontainsthesamestructuralelement.Weusedmoleculardockingapproachcombinedwithmoleculardynamics(MD)simulationtomodelthree-dimensional(3D)complexstructuresofSPD-304,zafirlukastandL-745,870intoCYP3A4,respectively.Theresultsshowthatthesethreedrugscanstablybindintotheactivesiteandthe3-methylenecarbonsofthedrugskeepareasonablereactivedistancefromthehemeiron.ThecomplexstructureofSPD-304-CYP3A4isinagreementwithexperimentaldata.Forzafirlukast,thecalculationresultsindicatethat3-methylenecarbonmightbethedehydrogenationreactionsite.DockingmodelofL-745,870-CYP3A4showsapotentialpossibilityofL-745,870dehydrogenatedbyCYP3A4at3-methylenecarbonwhichisinagreementwithexperimentinvivo.Inaddition,residuesinthephenylalanineclusteraswellasS119andR212playacriticalroleintheligandsbindingbasedonourcalculations.ThedockingmodelscouldprovidesomecluestounderstandthemetabolicmechanismofthedrugsbyCYP3A4.
简介:以化学沉淀法制备单相的铕离子掺杂硼铝酸盐红色荧光粉YAl3(BO3)4:Eu3+,考察了焙烧温度、掺铕量等因素对材料性能的影响,用X射线衍射、扫描电镜、激发光谱和发射光谱对荧光粉的结构、形貌和发光性能进行了表征.以尿素为沉淀剂,900℃焙烧沉淀前驱体可得到单相荧光粉YAl3(BO3)4:Eu3+,反应温度比传统高温固相法降低了300℃;沉淀法制备的荧光粉粒径分布范围小,无团聚现象,粒径约300nm.掺铕量为10%(物质的量比)时发光强度最大.在260nIn的紫外光激发下,Eu3+的5D0→F72的电偶极跃迁最强,发射光为618nm的红光.