Team:University College London/LabBook/Week8

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Contents

Monday 30.6.12

Aim: Repeat the gel from Expt 7.3 (week 7) with a smaller ladder and higher agarose percentage in order to detect the very small inserts of BBa_J23119 (35bp) and BBa_B0034 (12hp). Previous ladder used was 10037 bp, and this time we used a 25bp ladder.

Restriction Enzyme Digest Protocol 1

Step 1 - Thawing cells: Thaw all materials on ice

Step 2 - Adding Ingredient: Add the following ingredients to autoclaved/sterile eppendorf tubes

Component Amount (ul) (one enzyme used) Amount (ul) (two enzymes used)
dH20 2.5 1.5
Buffer 1x 1 1
DNA template 5 5
BSA 0.5 0.5
Enzyme 1 1 2
Enzyme 2 N/A 1


Step 3 - Addition of BioBrick: Flick contents gently and centrifuge.

Step 4 - Centrifuge:

RPM: 14000

Time: 1 minute

Temperature: 18oC

Step 5 - Digest Program: Place the samples on a thermocycler under the following conditions:

RPM: 550

Time: 2.5 hours

Temperature: 37oC

Step 6 - Denaturing Enzymes: If you are not running the samples on a gel immediately, denature the restriction enzymes by running the samples on a thermocycler under the following conditions:

RPM: 550

Time: 25 minutes

Temperature: 65oC


Electrophoresis Protocol

Preparing the Gel

Step 1: Within a conical flask, add 3ml 50X TAE, 1.5g Agarose, and 150ml RO water

Step 2: Heat for 1 min in microwave. Swirl. Heat again for 30s. If solution is clear stop. Else repeat.

Step 3: Cool solution under running cold water.

Step 4: Add 20ul ethidium bromide (normal concentration of EB solution is 500ug/ul)

Step 5: Pour into a sealed casting tray in a slow steady stream, ensuring there are no bubbles

Running a gel

Step 6: Add 1 part loading buffer to five parts of loading sample

Step 7: Position the gel in the tank and add TAE buffer, enough to cover the gel by several mm

Step 8: Add 5ul of DNA ladder to lane 1

Step 9: Add samples to the remaining wells

Step 10: Run at 100 volts for 1hour and 15 minutes

Imaging the Gel

Step 11: Place gel in GelDoc 2000 chamber

Step 12: Turn GelDoc 2000 chamber on 

Step 13: From computer: Quantity One > Scanner > Gel_Doc_Xr>Manuqal Acquire

Step 14: Alter the exposure/settings to give a clear image.

TAE - Tris-acetate-EDTA

EDTA - ethylenediamine tetraacetic acid

Results:The image below shows a 3.5% Agarose Gel of an Analytical Restriction Enzyme Digest for Expt 7.3. The high agarose concentration of the gel was intended to slow the progression of DNA fragments to enable us to detect the small inserts of BBa_J23119 and BBa_B0034. Accordingly, we used a the smallest available ladder, with fragments ranging from 25bp to 500bp. At the top of the gel it is possible to see the large fragments we detected on a 1000bp gel in Expt 7.3 Week 7. However, we had expected this gel to also demonstrate the BBa_J23119 insert (35bp) corresponding to letter A in Lane 1, and the BBa_B0034 insert, corresponding to letter B in Lane 3. No product was found. As expected, there was no product measurable against the 25bp ladder for the uncut plasmids in Lane 2 and Lane 4.

Conclusion:No product was detected for either BioBrick insert. However, we do no feel this necessarily proves the transformation failed, especially as we detected the correct plasmid backbone for each in week 7 (Expt 7.3). The modest nanodrop concentration obtained last week suggests that the concentration was not high enough to allow such a small fragment to be visualised. We are considering alternatives such as running a polyacrylamide gel, which is more sensitive to small fragments, or amplifying the fragment using PCR

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