| For many years staff scientists at New England Biolabs have been using their own line of optimized chemically competent E. coli cells for cloning and protein expression. Now when you are looking for a versatile cloning strain, rapid colony growth, or tight control of expression, you can benefit from the superior performance and high quality of these strains. |  |
Advantages of NEB Competent Cells
Strain Selection Chart
| Characteristics | Strain |
| Cloning and Sub Cloning Strains | |
| Fastest Growth – Colonies Visible After 6.5 Hours | |
| Versatile Cloning Strain | NEB 5-alpha High Efficiency NEB 5-alpha Subcloning Efficiency NEB 5-alpha Eletrocompetent |
| Toxic Gene Cloning | NEB 5-alpha F'Iq High Efficiency |
| Large Plasmid and BAC Cloning | NEB 10-beta High Efficiency NEB 10-beta Electrocompetent |
| dam/dcm Methyltransferase Free Plasmid Growth | dam–/dcm– |
| Protein Expression Strains | |
| Most Popular Protein Expression Strain | NEB Express High Efficiency |
| Control of IPTG Induced Protein Expression | NEB Express Iq High Efficiency |
| Most Popular T7 Protein Expression Strain | T7 Express High Efficiency |
| Control of IPTG Induced Protein Expression | T7 Express Iq High Efficiency |
| Tight Control of Protein Expressionby Inhibition of T7 RNA Polymerase | T7 Express lysY High Efficiency |
| Highest Level of Protein Expression Control | T7 Express lysY/Iq High Efficiency |
| For Crystallography Experiments / SeMet Labeling | T7 Express Crystal High Efficiency |
| Enhanced capability to correctly fold proteins with multiple disulfide bonds in the cytoplasm | SHuffle Express |
| Enhanced capability to correctly fold proteins with multiple disulfide bonds in the cytoplasm | SHuffle T7 Express |
| Tight control/expression of toxic proteins / Enhanced capability to correctly fold proteins with multiple disulfide bonds in the cytoplasm |
SHuffle T7 Express lysY |
| Routine T7 expression | BL21(DE3) |
Tunable T7 expression for difficult targets such as membrane proteins, toxic proteins and proteins prone to insoluble expression |
Lemo21(DE3) |
| Enhanced capability to correctly fold proteins with multiple disulfide bonds in the cytoplasm | SHuffle |
| Enhanced capability to correctly fold protein with multiple disulfide bonds in the cytoplasm and T7 expression | SHuffle T7 |
| Tight control/expression of toxic proteins / Enhanced capability to correctly fold proteins with multiple disulfide bonds in the cytoplasm and T7 expression |
SHuffle T7 lysY |
Strain Property Chart
| Transform Efficiency (cfu/µg) |
Strain | T1 Phage Resistant |
Library Construct -ion(1) |
Cloning/ Sub Cloning |
Blue/ White Screening |
laclq | lysY | Colonies Visible after 6.5h |
Endo- nucleaseI Deficient(2) |
Protease(3) Deficient |
F' | RecA- |
T7 RNA Polymer -ase |
Cytoplasmic disulphide bond formation(4) |
|
| NEB Turbo | 1-3x109 | K12 | √ | √ | √ | √ | √ | - | √ | √ | - | √ | - | - | - |
| NEB Turbo Electrocompetent | 1-4x1010 | K12 | √ | √ | √ | √ | √ | - | √ | √ | - | √ | - | - | - |
| NEB 5-alpha | 1-3x109 | K12 | √ | √ | √ | √ | - | - | - | √ | - | - | √ | - | - |
| NEB 5-alpha Subcloning | >1x106 | K12 | √ | √ | √ | √ | - | - | - | √ | - | - | √ | - | - |
| NEB 5-alpha Electrocompetent | 1-4x1010 | K12 | √ | √ | √ | √ | - | - | - | √ | - | - | √ | - | - |
| NEB 5-alpha F'Iq | 1-3x109 | K12 | √ | √ | √ | √ | √ | - | - | √ | - | √ | √ | - | - |
| NEB 10-beta | 1-3x109 | K12 | √ | √ | √ | √ | - | - | - | √ | - | - | √ | - | - |
| NEB 10-beta Electrocompetent | 1-4x1010 | K12 | √ | √ | √ | √ | - | - | - | √ | - | - | √ | - | - |
| dam–/dcm– | 1-3x106 | K12 | √ | √ | √ | - | - | - | - | √ | - | - | - | - | - |
| NEB Express | 0.6-1x109 | B | √ | √ | - | - | - | - | - | √ | √ | - | - | √ | - |
| NEB Express Iq | 0.6-1x109 | B | √ | √ | - | - | √ | - | - | √ | √ | - | - | √ | - |
| T7 Express | 0.6-1x109 | B | √ | √ | - | - | - | - | - | √ | √ | - | - | √ | - |
| T7 Express Iq | 0.6-1x109 | B | √ | √ | - | - | √ | - | - | √ | √ | - | - | √ | - |
| T7 Express lysY | 0.6-1x109 | B | √ | √ | - | - | - | √ | - | √ | √ | - | - | √ | - |
| T7 Express lysY/Iq | 0.6-1x109 | B | √ | √ | - | - | √ | √ | - | √ | √ | - | - | √ | - |
| T7 Express Crystal | 0.6-1x109 | B | √ | √ | - | - | - | - | - | √ | √ | - | - | √ | - |
| SHuffle | 1x106 | K12 | √ | - | - | - | √ | - | - | - | - | √ | - | - | √ |
| SHuffle T7 | 1x106 | K12 | √ | - | - | - | √ | - | - | - | - | √ | - | √ | √ |
| SHuffle T7 lysY | 1x106 | K12 | √ | - | - | - | √ | √ | - | - | - | - | - | √ | √ |
| SHuffle Express | 1x107 | B | √ | - | - | - | √ | - | - | √ | √ | - | - | - | √ |
| SHuffle T7 Express | 1x107 | B | √ | - | - | - | √ | - | - | √ | √ | - | - | √ | √ |
| SHuffle T7 Express lysY |
1x107 | B | √ | - | - | - | √ | √ | - | √ | √ | - | - | √ | √ |
| BL21(DE3) | 1-5x106 | B | √ | - | - | - | - | - | - | - | √ | - | - | √ | - |
| Lemo21(DE3) | 1-3x107 | B | √ | - | - | - | - | - | - | - | √ | - | - | √ | - |
(1) Restriction-deficient strain.
(2) Important for plasmid preparation.
(3) Lacks Lon and OmpT protease activity.
(4) Constitutively expresses a chromosomal copy of the disulfide bond isomerase DsbC.
Cloning
For cloning experiments choose from several high efficiency competent cell strains. These E. coli strains are T1 phage resistant and are endA deficient for high quality plasmid preparations. Additionally, all competent cells from NEB are free of animal products. NEB 5-alpha strains are enhanced DH5α™ derivatives, while NEB 10-beta is a DH10B™ derivative. NEB also offers a unique fast growing strain (NEB Turbo) and a dam–/dcm– strain.
Protein Expression
NEB offers several strains with varying levels of expression control, each with phage T1 resistance and extremely high transformation efficiencies. NEB Express is an enhanced BL21 derivative available with or without the added control of IPTG-induced expression of non-T7 plasmids from lacIq. T7 Express, an enhanced derivative of BL21 (DE3), is available with or without the added control of lacIq, and both versions can be purchased with or without the lysY feature for exceptional control of expression. LysY is a variant of T7 lysozyme lacking amidase activity, which make the cells less susceptible to lysis during induction, yet they retain the ability to inhibit T7 RNA polymerase. Basal expression of the target gene is minimized without inhibiting IPTG-induced expression. LysY is encoded on a single-copy miniF plasmid that does not require antibiotic selection for propagation. T7 Express lysY/Iq provides the highest level of expression control.
SHuffle strains enable disulfide bond formation in the cytoplasm. Normally, reductases in the E. coli cytoplasm keep cysteines in their reduced form, thereby preventing any disulfide bond formation in this compartment. The deletions of the genes for glutaredoxin reductase and thioredoxin reductase (Δgor ΔtrxB), allows disulfide bond formation in the cytoplasm with SHuffle. This combination of mutations is normally lethal, but the lethality is suppressed by a mutation in the peroxiredoxin enzyme (ahpC*). In addition, SHuffle expresses a version of the periplasmic disulfide bond isomerase DsbC which lacks its signal sequence, retaining it in the cytoplasm. This enzyme has been shown to act on proteins with multiple disulfide bonds, to correct mis-oxidized bonds and promote proper folding. The gene for the cytoplasmic DsbC is present on the chromosome.
BL21 (DE3) is available for routine T7 expression in addition to Lemo21(DE3) for tunable expression of difficult targets such as membrane proteins, toxic proteins and proteins prone to insoluble expression.
Formats
NEB provides these superior competent cell strains in several formats for your convenience. All are available as 50 µl single-use transformation tubes and many are available in larger, 200 µl tubes for multiple simultaneous reactions. Our most popular cloning strains are available as electrocompetent cells. NEB 5-alpha is also available in a lower efficiency, subcloning format for substantial value.
DH5α and DH10B are trademarks of Invitrogen Corporation.
