Size selective DNA precipitation protocol

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Solutions/reagents:

• DNA sample
  
  (DNA to be separated (e.g. PCR reaction mixture))
• PEG/MgCl2
  
  (30% (w/v) PEG 8000/30 mM MgCl2 (concentration of PEG 8000 can be varied to shift the size of the percipitated DNA. The concentration used here will remove DNA fragments with less than 300bp))
• TE buffer
  
  (10 mM TRIS-HCl, 1 mM EDTA, pH 8.0)
• buffer of choice

Equipment:

• Centrifuge
• Eppendorf tubes

Steps:

1. Measure out 50 µl of DNA sample into Eppendorf tube (1).
   Measure out 150 µl of TE buffer into DNA sample.
   Gently tap the mixture for a few secs.
   
2. Measure out 10 µl of PEG/MgCl2 into Eppendorf tube (1).
   
3. Vortex the mixture for a few secs.
   
4. Centrifuge at a speed of 10000 Xg for 15 mins at room temperature, gently aspirate out the supernatant and discard it.
   
5. Carefully remove supernatant not to disturb the pellet, which will be invisible.
   
6. Add buffer of choice to pellet.
   Add appropriate volume of buffer.
   Dissolve the pellet in the solution.
   

TOTAL TIME REQUIRED FOR THE COMPLETION OF THE PROTOCOL :~ 15 mins