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1、CentrifugesandRotorsAPPENDIX2CCentrifugationrunsdescribedinthisbookusuallyspecifyarelativecentrifugalforce(RCF;measuredin×g),correspondingtoaspeed(inrpm)foraparticularcentrifugeandrotormodel.Asavailableequipmentwillvaryfromlaboratorytolaboratory,theinvesti-gatormustb
2、eabletoadaptthesespecificationstoothercentrifugesandrotors.TherelationshipbetweenRCFandspeed(rpm)isdeterminedbythefollowingequation:RCF=1.12r(rpm1000)2whereristherotatingradiusbetweentheparticlebeingcentrifugedandtheaxisofrotation.Inmostcases,anaccurateconversionfrom
3、speedtorelativecentrifugalforce(orviceversa)canbeobtainedusingthemaximumvalueofr—orrmax—equaltothedistancebetweentheaxisofrotationandthebottomofthecentrifugetubeasitsitsinthewellorbucketoftherotor.TableA.2C.1providesrmaxvaluesforcommonlyusedrotorsmanufacturedbyDuPont
4、(Sorvall),Beckman,Fisher,andIEC.Therearesituations(e.g.,whereanadapterisusedtofitasmallertubeintoalargerrotorwell)wherermaxwillnotaccuratelyrepresenttheeffectiverotatingradius.Insuchcases,themanualfortherotorshouldbeconsultedtoobtaintheappropriatevalueofr.Asanalterna
5、tivetouseoftheaboveequation,thenomogramsinFiguresA.2C.1andA.2C.2makeitpossibletodeterminetheRCFwherespeedandrmaxareknown,orthespeedwhereRCFandrmaxareknown.Thisisdonebyaligningaruleracrossthetwoknownvaluesandreadingtheunknownvalueatthepointwheretherulercrossestheremai
6、ningcolumn.FigureA.2C.1shouldbeusedforcentrifugeruns<21,000rpm,whileFigureA.2C.2shouldbeusedforfasterspins.NOTE:Inthismanual,forspinsinvolvingmicrocentrifugesbuilttotheEppendorfstandard,ashortenedstyleofreferenceincludingonlythespeed(inrpm)isused.Alloftheseinstrument
7、shaveapproximatelythesamerotatingradius;hencethesamespeedwillyieldthesameRCFvaluefrommachinetomachine.Microcentrifugespinsmayalsobedescribedasat“topspeed”or“maximumspeed,”meaning12,000to14,000rpm,whichisthemaximumspeedforallEppendorf-typemicrocentrifuges.CAUTION:Dono
8、texceedmaximumrotorspeed!ForBeckmanultracentrifuges,themaximumspeedforeachrotorisdenotedbyitsname,e.g.,themaximumspeedoftheBeckmanV
