Invitrogen™ MultiShot™ StripWell BL21 Star™ (DE3) Competent Cells

MultiShot StripWell BL21 Star (DE3) chemically competent E. coli cells are cloning competent cells designed for applications that require high-level expression of non-toxic recombinant proteins from low copy number, T7 promoter-based expression systems. Engineered to carry the λDE3 lysogen that contains the T7 RNA polymerase gene under control of the lacUV5 promoter, these cells are pre-aliquoted in a rack containing 12 strips of 8 wells to increase productivity for throughput bacterial transformations.

Enhanced expression of nontoxic recombinant proteins
The BL21 (DE3) E. coli strain is one of the most popular host strains to produce recombinant proteins and adapted in research or industrial applications. IPTG is required to induce expression of the T7 RNA polymerase cascade system that in turn transcribes the T7 promoter regulated target gene.

The BL21(DE3) strain is derived from the E. coli B strain that does not contain the lon protease and is also deficient in the outer membrane protease OmpT. The lack of two key proteases reduces degradation of heterologous proteins expressed in the strains. Additionally, several other strain features make them especially suited for protein production, namely fast growth in minimal medium, a lower acetate production when grown in high glucose media, and an ability to reach high cell density.

MultiShot StripWell BL21 Star (DE3) Competent Cells offer enhanced mRNA stability due to a mutation in the RNaseE gene (rne131) that reduces levels of endogenous RNases and mRNA degradation, thereby increasing the stability of mRNA transcripts and increasing protein yield. The BL21 Star strain has higher basal expression of heterologous genes than BL21 (DE3) strains, due to the increased stability of mRNA. Thus, strains such as BL21-AI are recommended for toxic protein expression.

One Shot BL21 Star (DE3) Chemically Competent E. coli offer:
• Transformation efficiency of >1 x 10⁷ cfu/μg plasmid DNA 
• Ion and OmpT protease deficiency that reduces degradation of recombinant protein
• Optimized for use with low copy number, T7 promoter-based plasmids
• rne131 mutation that reduces levels of endogenous RNases and mRNA degradation
• hsdS mutation that allows efficient transformation of unmethylated DNA
• Fast growth in minimal medium and ability to reach high cell density

MultiShot StripWell flexible format
Each StripWell of eight connected tubes is designed with the same single-tube, single-use features as our One Shot format tubes. This format allows all steps of the transformation protocol, up to plating, to take place in the same tube, thereby saving time and reducing chance of contamination. After addition of DNA, MultiShot StripWell competent cells can be transformed by heat-shock at 42°C using a water bath, all in the same tube.

The StripWell tubes can be easily cut to permit transformations in a single tube, eliminating wasted aliquots of cells and avoiding freeze-thaws that can result in reduced transformation efficiency.

Benefits of the MultiShot StripWell format include:
• Increased productivity—suitable for high throughput experimentation
• Maximal flexibility—transform as few as 1 tube or as many as 96 from the StripWell rack
• Familiar convenience—add DNA directly to cells, heat shock, and recover in the same tube

Genotype
F^–ompT hsdSB (r_B^–, m_B^–) gal dcm rne131 (DE3)

Find the strain and format that you need
• We offer many E. coli strains and formats of chemically competent and electrocompetent cells to meet transformation needs.
• For high-throughput transformation, choose from our collection of MultiShot formatted comp cells.
• We offer a variety of systems for the expression of recombinant proteins in E. coli.