1.SUSPend5gofsilica(Sigma,S-5631)in50mlofPBS. 2.Allowthesilicatosettlefor2h. 3.Discardthesupernatantcontainingfineparticulatematter. 4.Repeatsteps2and3. 5.Spinfor2minat2000g.Discardthesupernatant. 6.Add3MNaItomakeafinalconcentrationof100mgsilica/ml. 7.Storethesilicasuspensioninthedarkat4C. 1.TotheagarosegelcontainingDNAfragments,addtwovolumesof6MNaI. 2.Incubatetheagarosein6MNaIat55Cfor5-10minwithoccasionalmixing. 3.Add10ulofthesilicasuspension.Vortexgently.Standfor5minatroomtemperaturewithoccasionalmixing.Onemgofthesilica(=10ulofthesilicasuspension)binds3-4.5ugofDNA. 4.Spinfor1mininamicrocentrifuge.Discardthesupernatant. 5.Pulsespin,andcarefullyremoveresidualliquid. 6.Suspendthepelletin500ulof50mMNaCl,10mMTrisHClpH7.5,2.5mMEDTA,50%(v/v)ethanol. 7.Spinfor1min.Discardthesupernatant. 8.Repeatsteps6and7. 9.Allowthepellettoair-dryfor10min. 10.Addanappropriatevolume(atleastonepelletvolume)ofTE.Vortexgentlytoresuspendthepellet,andstandfor5minatroomtemperaturewithperiodicagitation. 11.Spinfor1min.Transferthesupernatantintoanewmicrofugetube.PreparationofSilica
RecoveryofDNAfromAgaroseGelUsingtheSilicaSuspension.
