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Protocols

Notebook

Protocols

Calcium chloride transformation with heat shock in Escherichia coli DH5α


Materials


  • Sterile LB agar plate supplemented with the appropriate antibiotic (ampicillin 100 μg ml-1 or chloramphenicol 34 μg ml-1 - SIGMA-ALDRICH®);
  • Sterile liquid LB media (SIGMA-ALDRICH®);
  • Competent DH5α cells (Novagen) prepared through heat shock with calcium chloride;
  • Plasmidial DNA.

Methodology


  • Put the 0.5 mL microtube containing 50 μL competent cells aliquot on ice;
  • Add 20-50 ng of plasmidial DNA or 10 μL of ligation reaction to the competent cells. Mix by pipetting carefully;
  • Place the tube into a 42°C water bath for 2 min;
  • Return the tube to the ice for 5 min;
  • Add 200 μL of liquid LB;
  • Incubate at 37°C, 250 rpm for 45 min;
  • Plate the liquid LB containing the bacterial suspension on a LB agar plate with the appropriate antibiotic;
  • Incubate overnight (14- 16h) at 37°C.

Plasmid extraction



PureLink® Quick Plasmid Miniprep Kit-Life Technologies


Methodology


  • Cell Growth
      • After isolating a single colony from a LB agar plate, grow it in 6 mL of liquid LB within the appropriate antibiotic. Incubate overnight (14-16h) at 37°C in a shaking incubator.
  • Resuspension
      • Pellet the overnight culture in a 2 mL microtube and discard the supernatant. Repeat this step until the total liquid culture is finished. Resuspend the cell pellet in 240 μL of resuspension buffer by vortexing.
  • Lysis
      • Add 250 μL of the Lysis buffer. Mix by inversion 4-8 times and incubate at 37°C for 3-5 minutes. Do not exceed this period.
  • Neutralization
      • Add 350 μL of the neutralization solution. Mix by inversion 4-8 times and incubate at 37°C for 3-5 minutes. Do not exceed this time. Centrifuge at 16000 g for 10 minutes.
  • Washing
      • ransfer the supernatant to a new 1.5 mL microtube with the resin. Be careful not to transfer the white pellet. Add 650 μL of Wash buffer. Centrifuge at 16000 g for 1 minute. Discard the supernatant. Centrifuge again for 2-4 min to remove ethanol remains.
  • Elution of plasmidial DNA
      • Put the resin in a new 1.5 mL microtube. Add 50 μL of nuclease free water at 65°C. Centrifuge at 16000 g for 3 minutes and discard the resin. Store DNA at -20°C.

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