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61 changes: 61 additions & 0 deletions Plasmid_Prep_Without_Kit.md
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## Plasmid MidiPrep Without Use of Qiagen Kit

For some of our low-copy plasmid strains, the Qiagen Midi kit has failed to retrieve any usable plasmid, and when one needs a significant amount of plasmid, a multitude of minipreps can be expensive and time-consuming. This method will allow for significant plasmid yield without contamination of genomic DNA, and importantly, it is simple and cost effective.

### Reagents Required

Solution 1 = 10 mM EDTA pH 8.0, 1-20 μg/mL RNAase A. Store at 4°C. (Prepare 300 mL)
* To bring pH up, drop small amounts of 10M NaOH into solution while reading pH. Check with pH strips as well.

Solution 2 = (0.1 M NaOH, 1% SDS). Store at room temperature. (Prepare 200 mL)
* 2 grams total of SDS

Solution 3 = 250g/L Potassium Acetate, 15% vol/vol Acetic Acid. Store at 4°C. (Prepare 100 mL)
* Dissolve the 25 grams in 50 mL first and then bring the water volume up to 85. Then add the acetic acid.

### Regular Plasmid Prep (Miniprep)

1. Grow 2 mL bacteria (or 1.7 mL if growing in 2 mL tubes) with vigorous shaking or rolling in LB broth.
2. Transfer the saturated bacterial culture to a 2 mL microcentrifuge tube if culture was not grown in a 2 mL tube. Spin at ≥10,000xg for 30 seconds. Discard supernatant.
3. Resuspend the pellet in 100 μL Solution 1 by vortexing or pipeting.
4. Add 200 μL Solution 2 and mix by gentle swirling (it is very important to be very gentle or you
will get E. coli genomic DNA contamination in your plasmid prep).
5. Add 75 μL cold (4°C) Solution 3 and mix by gentle inversion (it is very important to be very
gentle or you will get E. coli genomic DNA contamination in your plasmid prep).
6. Place tubes in a rack stored at -20°C and store at -20°C for 1 minute.
7. Spin at max speed (≥10,000xg) for 5 minutes.
8. Transfer up to 375 μL of the supernatant to a clean 1.5 mL tube (avoid taking any white
precipitate).
9. Add 225 μL 100% isopropanol and mix by vortexing. Spin at max speed (≥10,000xg) for 5
minutes. Carefully discard the supernatant by pouring it out. Briefly spin down and remove any
residual supernatant with a pipet.
10. Add ≥ 1 mL 70% ethanol. Then pour away the ethanol.
11. Spin at ~10,000xg for 5 seconds. Pipet away the residual ethanol.
12. Leave on bench horizontally to dry for 2-5 minutes or speedvac for 1 minute.
13. Resuspend the pellet in 50 μL (or 50-100 μL) in one of the following: 2mM Tris pH 8.5, sterile
H2O, TE.

Protocol from Rahul Patharkar

### Large Plasmid Prep (Miniprep)

1. Grow 100 mL bacteria with vigorous shaking or rolling in LB broth.
2. Transfer 40 mL into the saturated bacterial culture to a 50 mL conical tube if culture was not grown in a 50 mL tube. Spin at ≥10,000xg for 5 minutes. Discard supernatant.
3. Resuspend the pellet in 2000 μL Solution 1 by vortexing or pipeting.
4. Add 4000 μL Solution 2 and mix by gentle swirling (it is very important to be very gentle or you
will get E. coli genomic DNA contamination in your plasmid prep).
5. Add 1500 μL cold (4°C) Solution 3 and mix by gentle inversion (it is very important to be very
gentle or you will get E. coli genomic DNA contamination in your plasmid prep).
6. Place tubes in a rack stored at -20°C and store at -20°C for 5 minutes.
7. Spin at max speed (≥10,000xg) for 15 minutes.
8. Transfer up to 375 μL of the supernatant to a clean 1.5 mL tube (avoid taking any white
precipitate).
9. Add 4 mL of 100% isopropanol and mix by vortexing. Spin at max speed (≥10,000xg) for 8
minutes. Carefully discard the supernatant by pouring it out. Briefly spin down and remove any
residual supernatant with a pipet.
10. Add ≥ 4 mL 70% ethanol. Then pour away the ethanol.
11. Spin at ~10,000xg for 5 seconds. Pipet away the residual ethanol.
12. Leave on bench horizontally to dry for 2-5 minutes or speedvac for 1 minute.
13. Resuspend the pellet in 300 μL in NF H2O.

14. THe elution should yield 100 to 400 ng/uL.