WangLab:Competent Cell Preparation
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Materials
500 ml 1x TB
- combine in H2O:
- 10mM PIPES (FW 342.4), 1.71g
- 15mM CaCl2.2H2O (FW 147.02), 1.1g
- 250mM KCl (FW 74.56), 9.32g
- adj PH to 6.7 with KOH, adj volume to 495 ml with water
- add MnCl2.4H2O (55mM, FW 197.9, 5.44g).
- Filter through the entire solution. Store at 4oC for up to 6 months
500ml SOC in 2L flask
- Desolve 10g Tryptone (2%)
- 2.5g Yeast extract (0.5%)
- add
- 1ml 5M NaCl (filtered sterile) (final 10mM)
- 5ml 250mM KCl (filtered sterile) (final 2.5mM)
- 2.5ml 2M MgSO4 (filtered sterile) (final 10 mM)
- adjust to 500 ml and autoclave
- after cool down,
- add 2.5ml 2M MgCl2 (filtered sterile) (final 10 mM)
- add 5ml 2M glucose (filtered sterile) (final 20 mM)
Procedure
- day 1: streak cells on a LB plate without ampicillin
- day 2: pick one colony and culture in 5 ml SOC 37oC.
- day 3:
- a. transfer 5 ml culture into 500 ml SOC, big flask
- incubate at RT, shake at 220 RPM, (9:00am-2:30pm)
- frequently check reading with 600 nm for cell density.
- b. put in ice, wait for 10 min, transfer to centrifuge tubes
- c. 4500 rpm, 10 min, spin,
- d. pellet should be small and thin, if large, do not use it.
- e. add 9.5ml TB, resuspend by gentle swirl, incubate 10 min in ice afterwards
- f. spin 3000 rpm, 10 min, 4oC.
- g. 20 ml TB for 250 ml culture with 0.6 OD, so 5-7ml for 500 ml with OD about 0.116. add 5 ml TB, gentle swirl and add 7% DMSO (350 ml), drop by drop while swirl.
- h. wait 10 min in ice.
- i. aliquote and put in liquid N2 immediately and keep in -80oC.
- a. transfer 5 ml culture into 500 ml SOC, big flask