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1、Step-by-StepExamples:AnalyzingDose-ResponseDatawithPrism3Adose-responsecurveisaplotofresponsetodrugtreatmentvs.drugconcentration.Sensitivitytoadrugactingataspecific,saturablereceptortypicallyspansalargeconcentrationrange,sodose-responsecurvesareusuallysemi-lo
2、garithmic,i.e.,theamountofdrugisplottedasthelogofdrugconcentration.Thisexamplewillshowyou(1)howtousePrismtofitasigmoidal(alsoknownas“logistic”)curvetoyourdose-responsedataand(2)onewaytocomparetwodose-responsecurvesstatistically.Supposewewanttoplottwodose-resp
3、onsecurves,showingtheaverageinvitroresponsetoanagonist,inthepresenceandintheabsenceofanantagonist,measuredintriplicate.Further,wewishtoincludeonthegraphazero-concentrationcontrolvalue.EntertheDataInthe WelcometoPrism dialogbox,select Createanewproject and Wor
4、kindependently.Underthe XColumn category,select Numbers,andunderthe YColumns category,choose 3replicatestocalculateerrorbars.Enterthedataasshownbelow.TheXvalues(agonistdose)aregivenasmolarconcentration,expressedinexponentialnotation.TheYvalues(response,inarbi
5、traryunits)goinsubcolumnsY1toY3Severalpointsaboutthisdataareworthnoting:Thedosageincrement(10nM,30nM,100nM,etc)shownintheXcolumnistypical.Thesevalueswillbelog-transformed,givingroughlyequalhorizontalspacingofdatapointsonthedose-responsecurve.Thesedataareagood
6、illustrationofPrism’suseofonlyoneXcolumn.AlthoughtheXvaluesfordatasetsAandBarenotthesame,wecancombinealltheXvaluesintoasinglecolumnandleaveY-valuecellsemptywhereappropriate.Thevaluesinrow1representthezero-concentration(noagonist)data.SinceourXcoordinateswillb
7、eplottedaslogarithms,andsincethelogof0isundefined,weapproximatethispointwithanXcoordinateof1.0e-010,about2logunitsbelowthelowest“real”Xvalue.Lateron,we’llshowhowtoplaceazeroontheXaxisforthisdatapoint.Forthisexample,we’reassumingthattheYvaluesdonotrequirecorre
8、ctionbysubtractionofabaseline—theminimumYvaluesarealreadyzeroes.IfyouwishtosubtractabaselinevaluefromeachYvalueinadataset,readabout automaticbaselinecorrectionsusingPrism inthe GraphPadQu
