Product Class: Competent Cell

NEB 5-alpha Competent E. coli (High Efficiency)

NEB does not add a dry ice surcharge to our competent cell shipments.
Also available in Electrocompetent format.
Catalog #SizeConcentration
C2987P1 x 96 well plate (20 µl/well)
C2987I6 x 0.2 ml/tube
C2987H20 x 0.05 ml/tube



  • DH5α™ derivative
  • Free of animal products
  • Transformation efficiency: 1 - 3 x 109 cfu/μg pUC19 DNA
  • Efficient transformation of unmethylated DNA derived from PCR, cDNA and many other sources (hsdR)
  • Activity of nonspecific endonuclease I (endA1) eliminated for highest quality plasmid preparations
  • Resistance to phage T1 (fhuA2)
  • Suitable for blue/white screening by α-complementation of the β-galactosidase gene
  • Reduced recombination of cloned DNA (recA1)
  • K12 Strain
Chemically competent E. coli cells suitable for high efficiency transformation in a wide variety of applications. Available in 3 convenient formats:

  • Single use 50 ul vials
  • 200 ul vials
  • 96-well plate: packed in a 96-well divisible polypropylene plate (Eppendorf twin.tec® PCR divisible plates


  • Versatile cloning strain
  • DH5α™ derivative


fhuA2 Δ(argF-lacZ)U169 phoA glnV44 Φ80 Δ(lacZ)M15 gyrA96 recA1 relA1 endA1 thi-1 hsdR17

Reagents Supplied

The following reagents are supplied with this product:

Store at (°C)Concentration
pUC19 Transformation Control Plasmid-200.05 ng/μl
SOC Outgrowth Medium41X

Advantages and Features


DNA Effects on Transformation Efficiency and Colony Output: The optimal amount of DNA to use in a transformation reaction is lower than commonly recognized. Using clean, supercoiled pUC19, the efficiency of transformation is highest in the 100 pg-1 ng range. However, the total colonies which can be obtained from a single transformation reaction increase up to about 100 ng.
Effect of heat shock time on NEB 5-alpha competent E.coli transformation efficiency: 50 μl of competent cells were transformed with 100 pg of pUC19 control DNA following the provided High Efficiency Transformation Protocol except heat shock time varied from 0 to 80 seconds.
Effect of DNA incubation time on NEB 5-alpha competent E.coli transformation efficiency: 50 μl of competent cells were transformed with 100 pg of pUC19 control DNA following the provided High Efficiency Transformation Protocol except DNA incubation time varied from 0 to 40 minutes.
Effect of outgrowth medium on transformation efficiency: 50 μl of NEB 5-alpha competent E.coli was transformed with 100 pg of pUC19 control DNA following the provided High Efficiency Transformation Protocol with the exception of varying the outgrowth medium. NEB SOC outgrowth medium delivers the highest transformation efficiency.
Take advantage of the low cost per transformation with NEB 5-alpha. Calculations were based on list price and recommended transformation volumes.
Benefit from the high transformation efficiencies of NEB 5-alpha: The transformation efficiencies of NEB 5-alpha and DH5α were compared using each manufacturers' recommended protocols. Values shown are the average of triplicate experiments.

Properties and Usage

Antibiotics for Plasmid SelectionWorking Concentration
Ampicillin100 μg/ml
Carbenicillin100 μg/ml
Chloramphenicol33 μg/ml
Kanamycin30 μg/ml
Streptomycin25 μg/ml
Tetracycline15 μg/ml

Storage Temperature


Shipping Notes

  • Ships on dry ice

Quality Control

Quality Control Assays

The following Quality Control Tests are performed on each new lot and meet the specifications designated for the product. Individual lot data can be found on the Product Summary Sheet/Datacard or Manual which can be found in the Supporting Documents section of this page.
  • Transformation Efficiency:
    The competent cells are tested for transformation efficiency and pass minimum release criteria. Transformation efficiency is defined as the number of colony forming units (cfu) which would be produced by transforming 1 μg of plasmid into a given volume of competent cells.

Supporting Documents

The following is a list of Safety Data Sheet (SDS) that apply to this product to help you use it safely.
The Product Summary Sheet, or Data Card, includes details for how to use the product, as well as details of its formulation and quality controls. The following file naming structure is used to name the majority of these document files: [Catalog Number]Datasheet-Lot[Lot Number]. For those product lots not listed below, please contact NEB at or fill out the Technical Support Form for appropriate document.


  1. CAUTION: This product contains DMSO, a hazardous material. Review the MSDS before handling.
  2. STORAGE AND HANDLING: Competent cells should be stored at -80°C. Storage at -20°C will result in a significant decrease in transformation efficiency. Cells lose efficiency whenever they are warmed above -80°C, even if they do not thaw.
  1. Can I store competent cells at -20°C instead of -80°C?
  2. Do you carry competent cells which are compatible with Gateway® Cloning?
  3. How can I increase transformation efficiency?
  4. How long should I incubate cells on ice after DNA has been added (NEB #C2987H and NEB #C2987I)?
  5. How should I calculate the transformation efficiency (C2987)?
  6. What are the solutions/recipes (C2987)?
  7. What are the strain properties (C2987)?
  8. What is the difference between NEB #C2987H and NEB #C2987I?
  9. What is the difference between NEB #C2988J and NEB #C2987H?
  10. What is the optimal heat shock time for this strain (NEB #C2987H and NEB #C2987I)?
  11. What type of competent cells are suitable for transformation of DNA constructs created using Gibson Assembly?
  12. Which strain of Competent E. coli should I use for general cloning?
  13. Which kind of transformation tubes should be used?
  14. What volume of DNA can be added into competent cells?
  15. Are NEB's competent cells compatible with the "Plate and Go" protocol?
  16. What is the shelf life for this strain (NEB #C2987H and NEB #C2987I)?
  17. Can the 96-well plate format of NEB 5-alpha Competent E.coli, NEB #C2987P, be separated into smaller sections?
  18. How does the transformation efficiency of the 96-well plate format (NEB #C2987P) compare to the other formats?
  19. What is the optimal heat shock time for the 96-well plate format NEB 5-alpha Competent E.coli (NEB #C2987P)?
  20. I am competing in the iGEM competition. Do you have any products that I should consider purchasing from NEB?
  1. 5 Minute Transformation Protocol (C2987H/C2987I)

  2. High Efficiency Transformation Protocol (C2987H/C2987I)

  3. High Efficiency Transformation Protocol for 96-well format (C2987P)
  4. 14 Minute Transformation Protocol (NEB #C2987H/C2987I)

Application Notes