This is the DNA Shuffling (or Sexual PCR) described by Stemmer. The DNA fragments are sheared into ~50bp fragments, then reassembled into a full-length library giving all permutations of combined mutations present in the original sample. It also induces additional point mutations and is therefore also a good error-prone pcr method.
DNase I Solution
2.0 Units/ml DNase I 50 mM Tris-HCl, pH 7.4 Prepare just before use 10 mM MnCl2
Note: The Qiagen RNase-Free DNase Set provides vials at 1500 units, dissolved 550 uL, so the concentration is 2.7 units/uL (2700 units/mL)
- Dissolve 2 to 5 μg of parent DNA in 10 μl of ddH2O (see Hint #1).
- Incubate the solution at 15 °C.
- Prepare 40 μl of DNase I solution and incubate at 15°C.
- Add 10 μl of the parent DNA solution to the 40 μl of DNase I solution at 15°C.
- Transfer 10 μl aliquots from the digestion reaction to individual tubes on ice containing 1 μl of 0.5 M EDTA, urea, and dye after 1, 2, 3, 5, and 10 min of incubation. (see Hint #2).
- Electrophorese the samples on a 12% TBE-Urea PAGE minigel along side an oligo sample around 50bp
- Place the gel on a TLC plate covered in saran wrap, cut the region similar in size to the 50bp oligo, put it in a microcentrifuge tube
- Add 500 uL or so of 1xTAE, and let shake at 37 for at least 2 hours to overnight to leach out the DNA fragments into solution
- Filter the liquid through a miniprep column or 0.2 micron column to remove bits of gel
- Measure the volume with a pipettman. Add 1/10th volume of ethanol and 2.5 volumes of ethanol. Chill 10 minutes at -20.
- Pass the liquid through a Zymo column or Qiagne blue column to collect the DNA, wash 2x with Qiagen PE Buffer or Zymo Wash Buffer to remove salts, spin 1 minute to dry, elute in 10 uL water
1. Combine the following in a microcentrifuge tube:
5 μl of 10X Taq Buffer 5 μl of dNTP Mix 10 μl of the purified fragments 2.5 Units of Taq Polymerase Add ddH2O to a total volume of 50 μl.
2. Incubate the reaction for 3 min at 94°C.
3. Amplify the DNA fragments in a thermocycler with the following program:
30 sec at 94°C 1 min at 55°C 1 min at 72°C Lengthen each extension step by an additional 5 sec per cycle. Repeat for 40 cycles (see Hint #6).
4. Visualize a small portion of the reaction by electrophoresis on a 2% (w/v) Agarose Gel (see Protocol ID#1265 and Hint #7).
1. Mix the following components in a microcentrifuge tube:
10 μl of 10 X Taq Buffer 10 μl of dNTP Mix 0.5 μM each Primer (Primer #1 and Primer #2) 1 μl of Assembly Reaction from Step #B3 5 Units of Taq Polymerase Add ddH2O to a total volume of 100 μl.
2. Amplify the DNA fragments in a thermocycler with the following program:
30 sec at 94°C 30 sec at 55°C 30 sec at 72°C Repeat for 30 cycles (see Hint #6).
3. Visualize a small portion of the reaction by electrophoresis on a 2% (w/v) Agarose Gel (see Protocol ID#1265 and Hint #8).
4. Electrophorese the DNA on a 2% (w/v) preparative Agarose gel (see Protocol ID #1265 and Hint #3) containing 0.5 μg/μl Ethidium Bromide (CAUTION! See Hint #9) to purify the DNA sequences for cloning into an expression vector.