MDS™42 ΔrecA Blue Chemically Competent Cell Kit

: MDS™42 ΔrecA Blue Chemically Competent Cell Kit

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SKU Product Manufacturer Price: Quantity
C-0095-05 C-0095-05K - MDS™42 ΔrecA Blue Chemically Competent Cells ***** 1
C-0095-10 C-0095-10K - MDS™42 ΔrecA Blue Chemically Competent Cells Scarab ***** 1
C-0095-20 C-0095-20K - MDS™42 ΔrecA Blue Chemically Competent Cells Scarab ***** 1
  • Maintain and propagate unstable clones and plasmids – pDNA vectors carrying direct repeats, inverted repeats or other sequences that result in pronounced secondary “stem-loop” structures are commonly unstable in standard E. coli hosts. Clean Genome® E. coli strains are frequently used for cloning sequences that suffer unwanted recombination events in other strains.
  • Accurate Plasmid Replication - Recombinogenic or mobile DNA elements such as Insertion Elements have been deleted from the Clean Genome® E. coli strains to ensure faithful replication of your construct.
  • Clone and Express “deleterious” genes – Clean Genome® E. coli strains’ natural defenses such as IS elements that mutate “deleterious” genes to stop the stress on the organism have been deleted so they cannot interfere with your experiments.
  • Higher Protein Yields – Removal unnecessary genes from the Clean Genome® E. coli strains redirects the cell’s energy to make more of your target and the removal of cryptic prophage prevents cell lysis, so your protein stays inside the cells.
  • Lower Background Induction than standard T7 Expression Strains –T7 RNA polymerase gene is under the control of a modified lac promoter/operator system which enhances sensitivity, and degree of repression conferred by LacI repressor protein.
  • Protein Expression using T7 Vectors – No recloning, use your existing T7 clones in the Clean Genome® E. coli host.


Using synthetic biology methods, the Escherichia coli K-12 genome was reduced by making a series of planned, precise deletions. The multiple-deletion series (MDS™) strains (1), with genome reduction of up to 15%, were designed by identifying non-essential genes and sequences for elimination, including recombinogenic or mobile DNA and cryptic virulence genes, while preserving robust growth and protein production. Genome reduction also led to unanticipated beneficial properties, including high electroporation efficiency and accurate propagation of recombinant genes and plasmids that are unstable in other strains. Subsequent deletions and introduction of useful alleles produce strains suitable for many molecular biology applications.


Figure 1: Multiple Deletion Strains tolerate "deleterious” genes.
A chimeric gene composed of VP60 of rabbit hemorrhagic disease virus fused to the B subunit of cholera toxin (CTX) was very unstable in E. coli. Individually, both genes were stable in E. coli HB101, C600 and DH10B, but pCTXVP60 carrying the fusion gene in the same hosts did not produce fusion protein and was recovered in low yields. All recovered plasmids contained mutations in the CTXVP60 open reading frame, virtually all resulting from IS insertions. In contrast, the recombinant plasmid was completely stable in MDS™; normal yields of plasmid DNA were obtained. Representative restriction patterns of pCTXVP60. (A) Plasmid DNA from MDS™42 was transformed and propagated in the indicated host, then digested with NcoI and EcoRI. A representative of each restriction pattern was purified and sequenced. M, molecular weight marker, 1 kbp ladder; 1, MDS™41, no insertion; 2, MDS™42, no insertion; 3, DH10B, IS10 insertion; 4, DH10B, IS10 insertion/deletion; 5, C600, IS5 insertion; 6, C600, IS1 insertion; 7, C600, IS1 insertion. (B) Relative position of the IS element insertion sites in the CTXVP60 reading frame determined for the five examples presented.

Figure 2: Plasmid stability in different host strains.
Left: during four subcultures of pT-ITR, a plasmid with viral LTR segments; Lane 0, isolated plasmid DNA before subculture, lanes 1-4, successive subcultures. Plasmid DNA was digested with restriction enzymes and analyzed by agarose gel electrophoresis. KpnI cuts the plasmid at a single site, but in MG1655 two bands indicate a deletion in the plasmid. MscI cuts at two locations, but in MG1655 a third intermediate band confirms that the plasmid is deleted. Right: Stability of four variants of a Lentiviral expression plasmid in MDS™42 ΔrecA and Stbl3™ (Life Technologies), showing the proportion of transformants containing intact plasmids (Table 2 BioTechniques 43:466-470 (October 2007))(2).


Kit Components
MDS™42 ΔrecA Blue Chemically Competent Cells
pUC19 Control DNA (10 pg/µl)
SOC Medium

MG1655 multiple-deletion strain (1)
The recA 1819 mutation is a complete deletion of ΔrecA.
The lacZ M15 deletion has been created in the genome to allow blue/white screening of inserts in plasmids using the α-complementing fragment of β-galactosidase.

Quality Control
Transformation efficiency is tested using pUC19 control DNA, performed in duplicate. Transformed cells are plated on LB plates containing 50 μg/ml carbenicillin. Transformation efficiency is =1x108 cfu/μg DNA.

Storage Conditions
Store components at –80°C. Do not store cells in liquid nitrogen.

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Patents & Disclaimers

Products are sold for non-commercial use only, under Scarab Genomics limited use label license: Limited Label Use.

Scarab is providing you with this Material subject to the non-transferable right to use the subject amount of the Material for your research at your academic institution. The Recipient agrees not to sell or otherwise transfer this Material, or anything derived or produced from the Material to a third party. NO RIGHTS ARE PROVIDED TO USE THE MATERIAL OR ANYTHING DERIVED OR PRODUCED FROM THE MATERIAL FOR COMMERCIAL PURPOSES. If the Recipient makes any changes to the chromosome of the Material that results in an invention in breach of this limited license, then Scarab will have a worldwide, exclusive, royalty-free license to such invention whether patentable or not. If the Recipient is not willing to accept the terms of this limited license, Scarab is willing to accept return of this product with a full refund, minus shipping and handling costs. For information on obtaining a license to this Material for purposes other than research, please contact Scarab’s Licensing Department. Scarab Genomics’ technology is covered by U.S. Pat. No. 6,989,265 and related foreign applications.

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