Experiments & Protocols

Contents

Competent Cells
Transformation Protocol
Miniprep

Competent Cells

Overview

Competent cells are ready to use bacterial cells that possess more easily altered cell walls by which foreign DNA can be passed through easily.

E. coli cells that have been specially treated to transform efficiently.

Materials

3ml 1M MnCl₂

15ml 1M CaCl₂

60ml 50mM MES

45ml glycerol

177ml ddH2O

Procedure

1. Overnight culture of VS45 cells are back-diluted to OD600 0.1 in 250 ml LB broth
2. The cells are then grown at 37˚C to OD600 0.6 and then harvested by centrifugation.
3. The cells are resuspended in 100 ml of prechilled buffer and incubated on ice for 60 minutes.
4. Harvest again by centrifugation (at 4˚C), and resuspended in 5 ml of pre-chilled buffer.
5. The resuspended cells can then be aliquoted (on ice), frozen using dry ice or liquid nitrogen, and stored at -80˚C.

References

Transformation Protocol

Overview
Materials
Procedure
References

Miniprep

Overview

The Miniprep is for purification of molecular biology grade plasmid DNA

This provides a rapid method to purify plasmid DNA using silica membrane column

Materials
Procedure

Add the provided RNase A solution to Buffer P1.

Mix the solution and store at 2–8°C

Add ethanol (96–100%) to Buffer PE before use

1. Pellet 1–5 ml bacterial overnight culture by centrifugation at >8000 rpm (6800 x g) for 3 min at room temperature (15–25°C).
2. Resuspend pelleted bacterial cells in 250 μl Buffer P1 and transfer it to a microcentrifuge tube.
3. Add 250 μl Buffer P2 and mix thoroughly by inverting the tube 4–6 times until the solution becomes clear. Do not allow the lysis reaction to proceed for more than 5 min. If using LyseBlue reagent, the solution will turn blue.
4. Add 350 μl Buffer N3 and mix immediately and thoroughly by inverting the tube 4–6 times.
5. Centrifuge for 10 min at 13,000 rpm (~17,900 x g) in a table-top microcentrifuge.
6. Apply 800 μl supernatant from step 5 to the QIAprep 2.0 spin column by pipetting. Centrifuge for 30–60 s and discard the flow-through.
7. Wash the QIAprep 2.0 spin column by adding 0.5 ml Buffer PB. Centrifuge for 30–60 s and discard the flow-through.
8. Wash the QIAprep 2.0 spin column by adding 0.75 ml Buffer PE. Centrifuge for 30–60 s and discard the flow-through
9. Centrifuge for 1 min to remove residual wash buffer.
10. Place the QIAprep 2.0 column in a clean 1.5 ml microcentrifuge tube. To elute DNA, add 50 μl Buffer EB (10 mM TrisCl, pH 8.5) to the center of the QIAprep 2.0 spin column, let stand for 1 min, and centrifuge for 1 min.
11. Add 1 volume of Loading Dye to 5 volumes of purified DNA. Mix the solution by pipetting up and down before loading the gel.

References