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Digestion of the original pMA plasmid containing LovTAP
Protocol: Restriction site digestion
- Look for the best pair of restriction sites, ideally with similar digestion temperatures and times.
- [http://tools.neb.com/NEBcutter2/ NEBcutter] for finding cutting enzymes.
- [http://www.neb.com/nebecomm/DoubleDigestCalculator.asp Double Digest Finder] for the parameters.
- Calculate the amounts required of:
- DNA
- Buffer (usually from 10x to 1x)
- BSA, if needed (usually from 100x to 1x)
- Enzymes (depends on the amount of DNA)
- Water
- Get the recommended buffer (and BSA if needed) from the freezer and let defreeze.
- Mix all the ingredients, except DNA, in a tube.
- Note: Enzymes should stay no longer than a couple of minutes out of the freezer. Don't touch the bottom of the tubes! Don't vortex!
- Distribute the mix in as many tubes as DNA samples and add the DNA.
- Keep in the Thermomixer at the recommended temperature.
Sowmya's recommended amounts (50 µl total solution):
- 5 µl of 10x buffer
- 0.5 µl of 100x BSA
- 1 µl of each enzyme
- 5 µl of DNA
- 37.5 (up to 50 µl) of water.
Protocol based on what was done on July the 4th.
The pMA plasmid was digested with EcoRI and HindIII to extract LovTAP for insertion into pcDNA3.1(+).
Gel electrophoresis of the LovTAP digestion
Protocol: Gel Electrophoresis
Agarose concentration depends on the size of the DNA to be run. We will mostly use 1%.
VOL is the desired volume of gel in ml:
CH Lab
- Add 0.01*VOL g of agarose to a clean glass bottle.
- Pour VOL/50 ml of 50xTAE in a graduated cylinder. Fill up to VOL ml with di water.
- Add the resulting VOL ml of 1xTAE to the glass bottle with agarose.
- Microwave, at 7, the bottle (loose cap!) until it boils.
- Carefully remove bottle (can be super heated!) and check for the total absence of particles. Microwave again if needed.
- Prepare a gel box, with comb, and fill it up with the agarose solution (maybe not the whole solution is needed).
- Add 0.05 µl per ml of gel in the box of Red Gel (it's in the iGEM drawer) and stirr until disolved.
- Wait until cold and solidified.
- Carefully remove comb.
- Place the box in the electrophoresis chamber.
- Fill up the electrophresis chamber with 1x TAE buffer.
- Add blue dye to the DNA samples (6x loading buffer, that is 10 µl in 50 µl of DNA solution).
- Inject 30 µl of ladder marker in the first well (that's 1 µg of DNA).
- Inject 60 µl of each DNA solution in the other wells.
- Set voltage to 70-90 V and run for 30-40 min, or until the dye reaches the last 25% of the gel length (DNA travels from - to +).
- Place the gel under the camera, cover, turn UV on and take photos!
Preparing the ladder:
- get 1kb ladder DNA from the freezer (500 µg/ml).
- for 30 charges, 30 µl per charge, we need 900 µl:
- 60 µl of 1kb ladder DNA
- 150 µl of dye (6x loading buffer)
- 690 µl of water
BM Lab
In this lab the gels are slightly different. The total volumes for the small, the medium and the large gel are respectively 60ml, 80ml and 90ml. As we use 0.5x TAE buffer instead of 1x, we can use higher voltages (170V seems to work fine). The gel should run 20-40 minutes, not more. As the gel is thinner, load less DNA (up to ~10ul).
The cut plasmid was run on a gel to separate the backbone from the gene of interest.
Gel extraction
Protocol: Gel Extraction
A gel extraction is used to select a fragment of DNA of a specific length
out of a solution composed of different fragments (ideally the difference
in length between the wanted fragment and the closest-sized fragment should
be more than 200bp). These fragments are often obtained after a
digestion.
The yeild for this procedure is typically very poor so a large amount of starting material, digested DNA in this case is required. We typically used 4 micrograms. The digestion products are loaded on a gel. Lanes on both sides of the one to be extracted should be empty to make cutting easier and avoid contamination with other fragments.
The gel should be run long enough for the bands to be spread out. This is particularly important if the fragment of interest is around the same length as other expected digestion products. UV light is necesary to observe the bands on the gel but exposure time should be minimized to avoid DNA damage. The fragment of interest is then excise and put in an Eppendorf (consider using a 2ml one).
To extract the DNA from the agarose we used Macherey-Nagel's "Nucleospin® Gel and PCR clean-up" kit. Its manual can be found here: [http://www.mn-net.com/Portals/8/attachments/Redakteure_Bio/Protocols/DNA%20clean-up/UM_PCRcleanup_Gelex_NSGelPCR.pdf Gel and PCR clean-up Manual]
Tips
- Cut away as much Agar as possible without slicing into the DNA. Excess agar will require more solvent to dissolve and will result in a poorer yeild upon elution.
- Minimize the DNA's exposure to the UV-light. UV will damage DNA and have negative effects on any subsequent reactions (for example, ligations can be 10'000x less effective when DNA has been exposed to too much UV light [http://openwetware.org/wiki/DNA_Ligation]
The gel slice was then purified using a Macherey-Nagel PCR cleanup and gel extraction kit.
- Comments
The digestion and the extraction appear to have worked. The final concentration of the purified product was on the order of 30 ng/ microliter.
