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1、LETTERSDirectforcemeasurementsonDNAinasolid-statenanoporeULRICHF.KEYSER,BERNARDN.KOELEMAN,STIJNVANDORP,DIEGOKRAPF,RALPHM.M.SMEETS,SERGEG.LEMAY,NYNKEH.DEKKER*ANDCEESDEKKER*KavliInstituteofNanoscience,DelftUniversityofTechnology,2628CJDelft,TheNetherlands*e-mail:N.H.Dekker@tudel
2、ft.nl;C.Dekker@tudelft.nlPublishedonline:1July2006;doi:10.1038/nphys344mongthevarietyofrolesfornanoporesinbiology,AANanoporeanimportantoneisenablingpolymertransport,for1Aexampleingenetransferbetweenbacteriaandtransport2ZofRNAthroughthenuclearmembrane.Recently,thishas3–56–10Yin
3、spiredtheuseofproteinandsolid-statenanoporesXassingle-moleculesensorsforthedetectionandstructuralanalysisofDNAandRNAbyvoltage-driventranslocation.ThemagnitudeoftheforceinvolvedisoffundamentalimportanceFStreptavidin–elinunderstandingandexploitingthistranslocationmechanism,bioti
4、nyetsofarithasremainedunknown.Here,wedemonstratetheZFfirstmeasurementsoftheforceonasingleDNAmoleculeinot11asolid-statenanoporebycombiningopticaltweezerswithionic-currentdetection.Theopposingforceexertedbytheλ-DNAopticaltweezerscanbeusedtoslowdownandevenarrestthetranslocationoft
5、heDNAmolecules.Weobtainavalueof0.24±0.02pNmV−1fortheforceonasingleDNAmolecule,Infraredlaserindependentofsaltconcentrationfrom0.02to1MKCl.Thisforcecorrespondstoaneffectivechargeof0.50±0.05electronsperbasepairequivalenttoa75%reductionofthebareFigure1Experimentalconfiguration.Atigh
6、tlyfocusedlaserbeamisusedtotrapDNAcharge.aDNA-coatedbeadnearasolid-statenanoporeimmersedinasalinesolution(leftItispossibletomanipulateDNAmoleculesusingelectricimage).ApplicationofavoltagedrivesanioniccurrentthroughthenanoporeandthefieldsbecauseDNAisnegativelychargedinsolution.C
7、onfiningnegativelychargedDNAintothenanopore.WhenaDNAmoleculeenterstheanelectricalfieldtoananoporeenablesthestudyofvoltage-nanopore(rightimage),anelectricalforceFelisexertedonthebeadwhichispulleddrivenDNAtranslocationwheretheforceisonlyappliedtotheoutofthetrapcentreoveradistance
8、ZuntiltheopticalforceFotandtheelectricalfewmonomersthatareins
