描述ElectroMAX™ Stbl4™ Competent Cells are specifically designed for cloning unstable inserts. As electrocompetent cells, they have one of the highest transformation efficiencies available (>5×109 cfu/µg), making them ideal for generating cDNA and genomic libraries and for cloning unstable inserts. These electrocompetent E. coli:• Are ideal for cloning unstable DNA—stabilizes direct repeat and retroviral sequences • Permit efficient cloning of methylated genomic DNA • Support blue/white screening • Are designed to deliver high-yield plasmid preparations for downstream applications • Provide transformation efficiencies of >5×109 cfu/µg Propagating unstable and large DNA with high transformation-efficiency cells Many competent cell strains have the recA1 genotype, which reduces recombination. However there are some instances when the DNA that you are trying to clone is still unstable in such cells, perhaps due to the presence of inverted or direct repeats, or GC-rich tracts. While such sequences are relatively common in eukaryotic genomes, they are rare in E. coli. Consequently, rearrangements may occur when these sequences are introduced into standard E. coli strains. Using ElectroMAX™ Stbl4™ Cells ElectroMAX™ Stbl4™ electrocompetent E. coli cells are a derivative of Stbl2™ cells and are ideal for the cloning of unstable inserts such as retroviral sequences, direct repeats, and tandem array genes. Furthermore, ElectroMAX™ Stbl4™ cells are useful for the generation of cDNA libraries using plasmid-derived vectors and are able to take up and maintain large plasmids (e.g., 50 kb cosmids and 100–200 kb P1 clones). The Stbl4™ cells also contain an F' episome, allowing them to serve as a host for single-stranded DNA such as M13mp cloning vectors. The lacZΔM15 marker provides α-complementation of the β-galactosidase gene from pUC or similar vectors, and can therefore be used for blue/white screening of colonies on agar plates containing Xgal or Bluo-gal and IPTG. The mcrA mutation and the mcrBC-hsdRMS-mrrdeletion allow cloning of genomic sequences which are methylated. Finally, the endA1 mutation greatly increases plasmid yield and quality. Genotype: mcrA Δ(mcrBC-hsdRMS-mrr) recA1 endA1 gyrA96 gal-thi-1 supE44 λ-relA1 Δ(lac-proAB)/F' proAB+lacIqZΔM15 Tn10 (TetR) |
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