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== Making chemically competent cells ==

=== Method Summary ===
This method describes how to prepare chemically competent e.coli.

=== Materials ===

==== Luria broth (LB) medium ====
* 0.5g/L sodium chloride 
* 10g/L tryptone 
* 5g/L yeast extract

or use any commercially available premixed LB medium powder

==== TS buffer ====
* 1x Luria broth (LB) medium
* 10% PEG 8'000 (3'300 or similar works as well)
* 5% DMSO
* 10mM MnCl2
* 10mM MgSO4

sterile filter through 0.2μm filter. Possible to store at 4ºC.

=== Method ===
# Pick several colonies from starter plate
# Grow cells in LB medium to an OD600 of 0.3-0.6
# Pellet cells by centrifugation (4000rpm, 4ºC)
# Discard supernatant
# Resuspend cells on ice into 1/20 volume of TS buffer by pipetting or vortexing
# Incubate cells on ice for 10 minutes
# Aliquot into sterile tubes and snap freeze in liquid nitrogen
# Store cells until needed in -80ºC freezer