MilliporeSigma™ Novagen™ Origami™ B (DE3) pLacI Competent Cells

Description

Origami B host strains are similar as the original Origami strain, except that they are derived from a lacZY mutant of BL21. Strain carries the pLacI plasmid producing extra Lac repressor.

Expression host strains for pETBlue™ and pTriEx™ vectors are lDE3 lysogens that also carry the compatible pLacI plasmid, encoding the lac repressor. The pLacI plasmid confers chloramphenicol resistance and provides enough lac repressor to inhibit transcription from the T7lac promoter in the absence of inducer. The NovaBlue host strain is recommended for initial cloning with pETBlue and pTriEx vectors due to its superior transformation efficiency and high yields of high-quality plasmid DNA. Note that these strains are not recommended for use with pET, pACYCDuet™, pCDF, pRSF, pCOLADuet™ or pETcoco™ vectors. Origami B host strains carry the same trxB/gor mutations as the original Origami strains, except that they are derived from a lacZY mutant of BL21 to enable pecise control of expression levels by adjusting the concentration of IPTG. Thus the Origami B strains combine the desirable characteristics of BL21, Tuner™, and Origami hosts in one strain background. The trxB and gor mutations are selectable on kanamycin and tetracycline, respectively; therefore, these strains cannot be used with the plasmids carrying kanamycin or tetracycline resistance genes. These strains also include the lon and ompT deficiences of BL21, which increase protein stability. DE3 indicates that the host is a lysogen of λDE3, and therefore carries a chromosomal copy of the T7 RNA polymerase gene under control of the lacUV5 promoter. Such strains are suitable for production of protein from target genes cloned in pET vectors by induction with IPTG.

Specifications

• Efficiency: Guaranteed efficiency: >2 x 10⁶ cfu/μg
• Content And Storage: ≤-70°C
• Quantity: 0.4 mL