Plasmids containing repetitive DNA sequences, such as those derived from retroviruses and lentiviruses, are susceptible to loss of integrity due to recombination events. In addition, GC- or AT- rich sequences (>70%) and sequences prone to the formation of secondary structures are notoriously difficult to clone. When cloning unstable DNA, choose a competent cell strain designed for the task. Bacteria with defective recombinases are more likely to faithfully replicate plasmids bearing unstable DNA inserts.
Use Stbl competent cells to avoid DNA recombination while cloning
Stbl competent cells express mutated forms of the RecA protein, rendering them recombination defective. Additional variations in genotype contribute to the ability of these strains to maintain plasmid integrity during cloning and replication. Notably, the Stbl3 strain demonstrated an exceptional maintenance of stability of an instability-prone lentiviral vector plasmid [1] and is the strain used in the seminal CRISPR-Cas9 protocol [2].
Compare Stbl competent cells for cloning unstable DNA
Three strains of Invitrogen Stbl competent cells are available, and each has properties that impact its performance with plasmids of various size and origin.
| Product |  |  |  |
|---|---|---|---|
| MAX Efficiency Stbl2 Chemically Competent Cells | Stbl3 Chemically Competent E. coli | ElectroMAX Stbl4 Competent Cells | |
| Recommended for | Cloning direct repeat retroviral sequences and tandem array genes | Cloning direct repeats found in lentiviral expression vectors | Generating complex cDNA and genomic libraries |
| Derived from strain | E. coli JM109/J5 | E. coli HB101 | Stbl2/E. coli JM109/J5 |
| Transformation efficiency | >1 x 109 cfu/µg | >1 x 108 cfu/µg | >5 x 109 cfu/µg |
| Type of transformation | Chemical/Heat shock | Chemical/Heat shock | Electroporation |
| Compatible plasmid size | >20 kb | >20 kb | >100 kb |
| Blue/white screening | – | – | |
| Contains F´ episome for making single-stranded DNA | – | – | |
| Available format(s) |
Still not sure which Stbl competent cells are right for your experiment?
References
Competent cells: Featured products
In addition to competent cells, we offer a broad suite of products for the cloning workflow.
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TOPO PCR
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Gibson Assembly
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Gibson Assembly cloning kits provide highly efficient, seamless cloning, enabling the assembly of multiple DNA fragments of varying lengths into any vector.
Resources
Have any questions on competent cells or transformation? Click on the resources listed below to access overviews, videos, genotype guides, and educational resources.
Review rich educational content on transformation workflow, troubleshooting, strategies, and selection guides.
Stay up-to-date on industry trends in molecular cloning with on-demand webinars.
Short articles and digital handbook for cloning applications
Access white papers and technical and application notes on molecular cloning.
Watch instructional videos on troubleshooting tips, how-to videos, and explainers related to molecular cloning.
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