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)-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)-T1^R is derived from 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. 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 >1x10⁷ cfu/μg when transformed with non-saturating amounts of pUC19 plasmid DNA.

dry ice

−70°C

S1797, SOC Medium

L7533, LB Agar EZMix^™ Powder

pUC19 Control DNA

BL21 (DE3)-T1^R Competent Cells