简介:以绿色荧光蛋白(GFP)基因作为报告基因,通过对比小鼠白蛋白启动子在不同来源细胞系中启动_GFP基因的转录活性,对小鼠白蛋白启动子的组织特异性进行了研究.结果发现,小鼠白蛋白启动子在小鼠肝癌细胞系Hepa1-6和人肝癌细胞系HepG2均有很强的转录起始功能,荧光显微镜下可以观察到GFP表达.Hepa1-6细胞在转染早期的48h内,CMV的启动子和增强子序列是小鼠白蛋白启动子转录活性的4倍.G418加压筛选2周后,CMV的启动子的转录活性下降到只有小鼠白蛋白启动子活性的1/2.转染入肝癌细胞系HepG22周后,荧光显微镜下可以观察到GFP表达.其他的细胞如中华仓鼠卵巢细胞系CHO和人肺癌细胞系PLA801中转染的小鼠白蛋白启动子不能启动GFP的表达,而对照CMV启动子控制下的GFP基因可在CHO和PLA801中表达.以上结果说明,小鼠白蛋白启动子仅在肝脏来源的细胞中可以起始下游基因的转录,在其他组织来源的细胞中不能起始转录,这表明小鼠白蛋白启动子具有肝脏组织特异的转录活性,但没有种属特异性.
简介:Wereportthefabricationprocessofpiezoelectriccellulosepaperandtheenhancementmethodofitspiezoelectricproperty.Stretchingmethodwithdifferentwet-drawingratioswasintroducedtoincreasethepiezoelectricpropertyofcellulosepaperduringregenerationprocess.ItisobservedthattheYoung’smodulusandthepiezoelectricchargeconstantsareverydependentonthedrawingratioandthedirectionofnanofibrilsofpiezoelectricpaper.Usingtheenhancedpiezoelectricproperty,weprovethattheflexibleregeneratedpiezoelectriccellulosecanbeappliedtothepotentialacousticapplicationssuchasthinpiezoelectricpaperspeaker.
简介:ThepropertiesofFeMnSiCrNishapememoryalloywereinvestigated.TheresultsshowthatthebestshapememoryeffectofFel4Mn6Si9Cr5Nialloyis85%.Thetransformationamountoftheε→γtransformationisnotcompleteafterheatingthealloyto1000K,AsandAfpointsdropwithincreasedtransformationenthalpy(△Hγ→ε)bythermalcyclingandincreasedprestrain.Thealloyshowsalsogoodcreepandstressrelaxationresistance.Inaddition,thealloyhavingatensileforceof20kNandasealingpressureof6MPacansatisfyrequirementsforpossibleindustrialapplicationonpipejoints.
简介:Thispaperdescribesanovelwavelet-basedapproachtothedetectionofabruptfaultofRotorcraftUnmannedAerialVe-hicle(RUAV)sensorsystem.Byuseofwavelettransformsthataccuratelylocalizethecharacteristicsofasignalbothinthetimeandfrequencydomains,theoccurringinstantsofabnormalstatusofasensorintheoutputsignalcanbeidentifiedbythemulti-scalerepresentationofthesignal.Oncetheinstantsaredetected,thedistributiondifferencesofthesignalenergyonalldecomposedwaveletscalesofthesignalbeforeandaftertheinstantsareusedtoclaimandclassifythesensorfaults.
简介:microRNA(miRNA)是一类长度为19-25个核苷酸的非常保守的非编码小RNA分子,在真核生物体内通过与mRNA的3'非翻译区序列不完全互补结合促使mRNA降解或抑制翻译,从而在转录后水平调控基因表达。miRNA在生物体内参与了细胞增殖与凋亡、生长发育、代谢活化、DNA修复等一系列生物学过程,与多种疾病尤其是肿瘤的发生发展密切相关。对miRNA的功能研究已发展到其分子机制层面,大量集中于其靶基因的预测和鉴定及调控相关表观遗传因子,为疾病的诊断、治疗及预后提供了新的线索。我们就miRNA的合成、功能研究及miRNA在临床上的应用前景做简要综述。
简介:Abiomimetichipjointsimulatorthatcanbeusedtoevaluatetheoutcomeofthecementedtotalhipreplacementhasbeendesigned,manufacturedandevaluated.Thesimulatorproducesmotionintheextension/flexionplane,withasockettorotateinternal/externally.Atthesametimeadynamicloadingcycleisapplied.Avalidationtestwasperformedonacementedfemoralstemwithinanovelcompositefemur.Thebonequalityhasastrongeffectonthestemmigrationandontheintegrityoftheinterfaces.Themigrationofthestemisacombinationof3-Dtranslationandrotationofthestem.Underthesameloadingconditions,weakboneallowsmorestemmigrationthanstrongbone.Thereisagreatdecreaseinthestrengthofthestem-cementinterfaceafterthedynamictest,andtheweakbonecompositeexhibitedagreaterreductionininterfacialstrengththanthestrongbonecomposite.Thedecreaseoftheinterfacialstrengthindicatesthattheprimarybondingbetweenthestemandthecementmantlehaddeterioratedandtheintegrityofstem-cementinterfacewasdamaged.Thestudydemonstratesthevalueofusingahipjointsimulatortoinvestigatestemmigrationandinterfaceintegritywithinthecementedhipreplacement,suggestingthatmethodcanbeusedforinvitroevaluationofthebiomaterialsusedinthecementedhipreplacements.
简介:传统认为只有真核生物才有蛋白质糖基化修饰现象,虽然在原核生物细胞中发现糖蛋白的存在已经有数十年,但是没有引起我们足够的重视。最近,在细菌中发现了蛋白质的糖基化修饰系统,最具代表性的是空肠弯曲弧菌的Ⅳ-糖基化修饰系统、脑膜炎奈瑟球菌和绿脓杆菌的0-糖基化修饰系统。这些糖基化修饰系统已成功地转移到大肠杆菌中,并且独立发挥其糖基化修饰作用。寡糖转移酶在修饰过程中起关键作用,且寡糖转移酶对糖底物的特异性要求非常低,这使得按照我们的需求来“定制糖蛋白”成为可能,并标志着“原核生物糖基工程”的到来,这将为糖结合疫苗的发展提供良好的契机。