How do I use powdered silica to isolate DNA from agarose gels?
To purify DNA from agarose gel, weigh the gel slice. Add 2-3 ml NaI solution per gram of gel. Incubate at 37-50 degrees C, mixing frequently until agarose is totally dissolved. Add 1 microliter of glass slurry per microgram of DNA, mix. Incubate on ice 5-10 mins, mixing occasionally. Spin 5-10 seconds in microfuge, remove and discard supernatant. Wash glass pellet with 250 microliter NaI (or 10 x volume of silica, whichever is larger). Spin and wash pellet 2-3 times with NEET wash (same volume). Dry pellet well, removing all residual liquid (air dry or use Kimwipe carefully). Resuspend pellet in H2O or TE (> 10 microliter) and elute DNA at 50 C for 5-10 mins. Spin 1 min in microfuge and remove eluted DNA in supernatant. The DNA is now ready for ligation, restriction, radiolabelling etc. This proceduure is normally used only on gels run in TAE or Tris phosphate buffer, but it can be used on borate gels if necessary. One researcher reports success by melting the DNA for longer than usual
