Preparing chemically competent cells

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• Grow a 5-25mL culture to an OD₆₀₀ of 0.2 0.5
• Centrifuge for 10 minutes at 3000rpm and 4^oC.
• Remove supernatant and replace with 10% original volume TSS.
• Make 100uL aliquots and store at − 80^oC.

TSS (50 mL)

• 5g PEG 8000
• 1.5 mL 1M MgCl2
• 2.5 mL DMSO
• LB to 50 mL