dna表面密度的计算

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1、DNA表面密度的计算[1]ThesurfacedensityofDNA,morespecificallythenumberofnucleotidephosphateresidues,iscalculatedfromtheamountofcationicredoxmarkermeasuredattheelectrodesurface.Thesaturatedamountofcharge-compensatingredoxmarkerintheDNAmonolayer,determinedusingchronocoulometry,isdirectlyproportionaltothe

2、numberofphosphateresiduesandtherebythesurfacedensityofDNA.Thismethodpermitsquantitativedeterminationofbothsingle-anddouble-strandedDNAatelectrodes.Surfacedensitiesofsingle-strandedDNAwerepreciselyvariedintherangeof(1-10)*1012molecules/cm2,asdeterminedbytheelectrochemicalmethod,usingmixedmonola

3、yers.Wemeasuredthehybridizationefficiencyofimmobilizedsingle-strandedDNAtocomplementarystrandsasafunctionoftheimmobilizedDNAsurfacedensityandfoundthatitexhibitsamaximumwithincreasingsurfacedensity.WehavequantifiedthesurfacedensityofDNAbytakingadvantageoftheelectrostaticattractionofspecificredo

4、xcationswiththenucleotidephosphatebackbone.TherearetwotypesofinteractionsforsmallredoxmoleculeswithDNA:electrostaticattractionandintercalation.Redoxcationsexchangefornativecounterionsassociatedwiththenucleotidephosphateresiduesoftheprobe.Theamountofredoxmarker“electrostaticallytrapped”attheDNA

5、-modifiedelectrodeisthendeterminedusingchronocoulometry.Atsaturationcoverageoftheredoxmarker,thesurfacedensityoftheprobeiscalculatedassumingcompletechargecompensationoftheDNAphosphateresiduesbyredoxcations.Astrongappealofthisapproachisthatthismeasurement,unlikemeasurementsusingothernoncovalent

6、labels,isinsensitivetoboththebasecompositionandthechainorder(single-strandedvsduplex).Themeasuredredoxmarkerisdirectlyproportionaltothenumberofphosphategroupspresentatthesurface.Anattractiveaspectofchronocoulometry(计时库伦分析法)isthatthedoublelayerchargeandthechargeduetoreactionofspeciesadsorbedont

7、heelectrodesurfacecanbedifferentiatedfromthechargeduetoreactionofredoxmoleculesthatdiffusetotheelectrodesurface.MCH的作用：liftstheDNAfromthesurfacetoaconformationwhereeachprobeisimmobilizedsolelythroughthethiolate.[1]固定DNA及MCH的方法[2]：atwo-s