XL2-Blue MRF? ultracompetent cells are high-efficiency derivatives of our XL1-Blue MRF? supercompetent cells.  Using ultracompetent cell technology, we have achieved transformation efficiencies of greater than 5 × 10⁹ transformants/?g of pUC18 DNA, making these ultracompetent cells an ideal choice for high-efficiency cloning. The XL2-Blue MRF? (Minus Restriction) strain is deficient in all known restriction systems (McrA–, McrCB–, McrF–, Mrr–, HsdR–), preventing cleavage of cloned DNA that carries cytosine and/or adenine methylation, which is often present in eukaryotic DNA and cDNA.   XL2-Blue MRF? cells are restriction minus. The strain is endonuclease deficient (endA), greatly improving the quality of miniprep DNA, and recombination deficient (recA), helping to ensure insert stability. These cells allow blue-white screening for recombinant plasmids.

Efficiency: ≥5 x 10⁹ transformants/?g of pUC18 DNA
Resistant to tetracycline and chloramphenicol.