Berglund:BL21 Star cells

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Preparation of CaCl2 (heat-shock) competent cells

Grow culture to an OD600 between 0.4 and 0.6
place on ice for 15 minutes
spin down cells at 4000xg
resuspend gently in half volume of ice cold 50mM CaCl2
Let sit on ice for 30 min
spin down
resuspend gently in 1/20 volume of ice cold 50mM CaCl2 + 10% glycerol

incubate at least 1 hr on ice

transform 200µl directly or quick freeze in a dry ice/ethanol bath and store at -80C

add 1µl plasmid and heat shock for 45 seconds at 42 degrees in a water bath