BL21（AI） Competent Cells

1. Competent cells should be used immediately after thawing and should not be left in ice for too long.
2. Do not aspirate competent cells with a pipette，just flick your finger to mix well.
3. When inducing protein expression，the IPTG concentration is optional (0.1-2 mM). This product is a competent made of Escherichia coli BL21 (AI). BL21 (AI) is an E. coli B/r strain，derived from BL21 strain，which is a defective strain of Lon protease and extramembrane protease OMPT，the absence of these two enzymes effectively prevents the degradation of heterologous proteins in E. coli. The addition of L-arabinose to the medium induces the expression of T7 RNA polymerase downstream of the araBAD promoter，thereby promoting the expression of the target protein. The addition of glucose to the medium inhibits the expression of T7RNA polymerase downstream of the araBAD promoter，thereby inhibiting the expression of the protein of interest. BL21(AI) competent cells are suitable for use with any T7 promoter-based expression vector and are capable of high levels of recombinant protein expression. Because the strain is able to efficiently regulate T7 RNA polymerase levels in vivo，BL21(AI) competent cells are able to express proteins that are toxic to other BL21 cells or inhibit growth. The yield of common recombinant protein in BL21 (AI) strain was comparable to that of other BL21 strains. For most of the toxic proteins，the yields obtained in the BL21 (AI) strain were higher than those obtained in the BL21 (DE3) pLysS strain or BL21 (DE3) strain. BL21(AI) competent cells were fabricated by a special process，and the transformation efficiency of the pUC19 plasmid was > 108 cfu/μg DNA. Genotype: F-ompThsdSB(rB-mB-)galdcm araB::T7RNAP-tetA} Procedure: 1. Remove the competent cells from the -80℃ freezer，put them in ice for 5 min，add the plasmid of interest or ligation product，flick to mix evenly，and incubate in ice for 30 min; 2. Put it in a 42°C water bath for 90s，immediately insert it into ice and let it stand for 2-3min; 3. Add 900 μL of LB liquid medium and incubate at 220 rpm at 37℃ for 60 min; 4. Centrifuge at 5000 rpm for one minute to collect bacteria，leave about 100 μl of supernatant and gently pipette the resuspended bacterial block and apply it to a 2YT or LB plate containing the corresponding antibiotic，and place in an incubator at 37°C overnight.