BL21 - Discontinued

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Chemically competent E. coli cells suitable for transformation and protein expression. This strain does not express the T7 RNA polymerase.

Features & Benefits

  • High efficiency - available in ≥107 cfu/μg, perfect for routine subcloning
  • Protease deficient - for high protein expression
  • Convenient size - small aliquots reduce waste


  • Non-T7 promotor protein expression


BL21 competent cells are a general expression host for protein expression from vectors containing E. coli promotors such as trc, tac, lPL and araD. This strain lacks a T7 polymerase gene and can be used for non-T7 RNA polymerase protein expression systems.

For T7 promotor driven protein expression, this strain requires infection with Lambda CE6 bacteriophage, which provides the T7 RNA polymerase. OmpT protease mutations minimize proteolytic degradation of expressed proteins.


Genotype: F- ompT hsdSB(rB-mB-) gal dcm




Chemically Competent Cells

10 x 100µl

pUC19 control vector (100pg/µl)


Storage & Stability

All kit components should be stored at -80°C upon receipt. When stored under the recommended conditions and handled correctly, full activity of the kit is retained until the expiry date on the outer box label.

Shipping conditions

Shipped on Dry Ice or Blue Ice.

Other researchers use:

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