- Transformation efficiency: 1–3 x 107 cfu/µg pUC19 DNA
- BL21(DE3) containing the Lemo System™
- Tunable T7 Expression Strain for difficult targets: membrane proteins, toxic proteins and proteins prone to insoluble expression
- Deficient in proteases Lon and OmpT
- Resistant to phage T1 (fhuA2)
- Lemo System™ maintained by chloramphenicol
Lemo21(DE3) offers the host features of BL21(DE3) while also allowing for tunable expression of difficult clones. Tunable expression is achieved by varying the level of lysozyme (lysY), the natural inhibitor of T7 RNA polymerase. The level of lysozyme is modulated by adding L-rhamnose to the expression culture at levels from zero to 2000 µM. When Lemo21(DE3) is grown without rhamnose, the strain performs the same as a pLysS containing strain. However, optional addition of rhamnose tunes the expression of the protein of interest. For difficult soluble proteins, tuning the expression level may also result in more soluble, properly folded protein.
- Tunable T7 expression for difficult targets
GenotypefhuA2 [lon] ompT gal (λ DE3) [dcm] ∆hsdS/ pLemo(CamR)
λ DE3 = λ sBamHIo ∆EcoRI-B int::(lacI::PlacUV5::T7 gene1) i21 ∆nin5
pLemo = pACYC184-PrhaBAD-lysY
The following reagents are supplied with this product:
|Store at (°C)||Concentration|
|L-rhamnose solution||500 mM|
|pUC19 Transformation Control Plasmid||-20||0.05 ng/μl|
Advantages and Features
Properties and Usage
|Antibiotics for Plasmid Selection||Working Concentration|
- Ships on dry ice
Quality Control AssaysThe following Quality Control Tests are performed on each new lot and meet the specifications designated for the product. Individual lot data can be found on the Product Summary Sheet/Datacard or Manual which can be found in the Supporting Documents section of this page.
- Transformation Efficiency:
The competent cells are tested for transformation efficiency and pass minimum release criteria. Transformation efficiency is defined as the number of colony forming units (cfu) which would be produced by transforming 1 μg of plasmid into a given volume of competent cells.
Research Use Only
- RESEARCH USE ASSURANCE STATEMENT
The buyer and user have a non-exclusive sub-license to use this system or any component thereof for RESEARCH PURPOSES ONLY, based upon agreement to the following assurances:
Transfer of the host cells that contain the cloned copy of the T7 gene 1 to third parties is explicitly prohibited. This information applies to E. coli ER2566, ER2833, ER3011, ER3012, ER3013 and ER3021, SHuffle® T7, SHuffle® T7 LysY, SHuffle® T7 Express, SHuffle® T7 Express LysY and their competent derivatives, C2566, C2833, C3010, C3013, C3016, C3022, C3026, C3027, C3029 and C3030 when povided separately or when provided in combination with appropriate vectors for said systems.
The Lemo System™ (pACYC184-rhaBAD-lysY): This construct is referred to as pLemo in Wagner et al. (2008) Proc. Natl. Sci. USA 105:14371–14376. Tunable T7 expression is achieved by modulating the level of T7 lyosyme (LysY) via L-rhamnose induction of the rhaBAD promoter.
The Lemo System™ is owned by Xbrane Biosciences AB (Stockholm, Sweden) and has been exclusively licensed to New England Biolabs, Inc. for the manufacture and distribution of Lemo21(DE3) Competent E. coli.
The purchase of this product conveys to the non-commercial purchaser the non-transferable right to use the purchased amount of the product and components of the product for research use only conducted by the researcher. For commercial purchasers using this product for research, the purchase of this product conveys to the purchaser the non-transferable right to use the purchased amount of the product and components of the product for a six (6) month evaluation period after the date of purchase for research use only. After the six (6) month evaluation period, continued use of this product for either commercial research or commercial purposes may require a commercial license. For more information, contact New England Biolabs, Inc. at firstname.lastname@example.org. Commercial research and/or commercial purposes means any activity by a party for consideration and may include, but it not limited to: (1) use of the product or its components in manufacturing; (2) use of the product or its components to provide a service, information or data; (3) use of the product or its components for therapeutic, diagnostic or prophylactic purposes; or (4) resale of the product or its components, whether or not such product or its components are resold for use in research. If the Purchaser is unwilling to accept the limitations of the limited-use statement, NEB is willing to accept return of the products with a full refund.
- CAUTION: This product contains DMSO, a hazardous material. Review the MSDS before handling.
- STORAGE AND HANDLING: Competent cells should be stored at -80°C. Storage at -20°C will result in a significant decrease in transformation efficiency. Cells lose efficiency whenever they are warmed above -80°C, even if they do not thaw.
- Chloramphenicol must be added at 30 μg/ml to maintain the Lemo System™.
- What are the solutions/recipes (C2528)?
- What are the strain properties (C2528)?
- Why are there no colonies or no growth in liquid culture (C2529)?
- Why is induced protein insoluble (C2528)?
- Why is there no protein visible on gel or no activity (C2528)?
- Can I store competent cells at -20°C instead of -80°C?
- Which kind of transformation tubes should be used?
- What volume of DNA can be added into competent cells?
- What is the shelf life for this strain (NEB #C2528H)?
- Are NEB's competent cells compatible with the "Plate and Go" protocol?