BL21 Competent Cells, Uni-pack 

Sigma's BL21-T1^R competent E. coli cells are grown and made chemically competent using an optimized procedure specific to the strain, followed by strain verification and efficiency testing. The cells are provided in frozen 50 μl aliquots for convenience. Each aliquot can be used for a single transformation.

BL21(DE3)pLysS-T1^R competent Escherichia coli is an expression strain suitable for high level induction and expression of genes from any T7 promoter-based expression vector. BL21(DE3)pLysS-T1^R is a B/r strain bacteria which naturally lacks the lon protease and is also deficient in the outer membrane protease ompT. The absence of proteolytic activity from these two proteases may reduce degradation of some heterologous proteins expressed in the strain. The DE3 designation indicates the strain is lysogenic for a lambda prophage containing an inducible T7 RNA polymerase, which is under the control of the lacUV5 promoter. T7 RNA polymerase expression is induced by addition of 1 mM IPTG to the culture. The pLysS plasmid expresses T7 lysozyme, a natural inhibitor of T7 polymerase, allowing for improved transcriptional control and reduction of "leaky" expression. The pLysS plasmid also renders the cell resistant to chloramphenicol (Cm^R) (5 μg/ml in liquid media and 25 μg/ml in plates) and contains the p15A origin. The p15A origin allows pLysS to be compatible with plasmids containing the ColE1 or pMB1 (derivative of pBR322) origin. In addition, the tonA genotype confers resistance to the lytic bacteriophages T1 and T5 for protection of clonal stocks.

The cells have a transformation efficiency of ≥5x10⁶ cfu/μg when transformed with non-saturating amounts of pUC19 plasmid DNA.

dry ice

−70°C

L7533, LB Agar EZMix^™ Powder

S1797, SOC Medium

BL21 (DE3) pLysS-T1^R Competent Cells

pUC19 Control DNA