Product Class: Other

NEB® 5-alpha Electrocompetent E. coli

This product is currently on backorder.  We recommend the chemical competent version, NEB 5-alpha Competent E. coli (NEB #C2987H/I) as an alternative. If you can only use electrocompetent cells for your application, please contact our Customer Service Team to explore further options.  

Having trouble opening your tubes? NEB Tube Opener can help!

Product Introduction

NEB 5-alpha Electrocompetent Competent E. coli is a derivative of the popular DH5α. It is T1 phage resistant and endA deficient for high-quality plasmid preparations. 

  • Optimized for high efficiency transformation by electroporation
  • No dry ice surcharge on competent cell shipments
  • Outgrowth medium included
  • Free of animal products
  • Also available in High efficiency chemical format
  • Refer to our Electroporation Tips
Bioz Badge Exists : True
Catalog # Size Concentration
C2989K 6 x 0.1 ml 0

Product Information



  • DH5α™ derivative
  • Transformation efficiency: >1 x 1010 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
  • Suitable for blue/white screening by α-complementation of the β-galactosidase gene (Φ80Δ lacZM15)
  • Resistance to phage T1 (fhuA2)
  • Reduced recombination of cloned DNA (recA1)
  • K12 Strain
  • Free of animal products

NEB 5-alpha Electrocompetent E. coli cells are optimized for high transformation efficiency by electroporation. These cells are ideal for DNA library constructions and all cloning purposes.


fhuA2Δ(argF-lacZ)U169 phoA glnV44 Φ80Δ (lacZ)M15 gyrA96 recA1 relA1 endA1 thi-1 hsdR17

Reagents Supplied

The following reagents are supplied with this product:

NEB # Component Name Component # Stored at (°C) Amount Concentration
  • C2989K     -80    
Product Categories:
Cloning Competent Cell Strains Products

Advantages and Features


Electroporation Tips
  1. Electroporation cuvettes and microcentrifuge tubes should be pre-chilled on ice. 
  2. Electrocompetent cells should be thawed on ice and suspended well by carefully flicking the tubes. 
  3. Once DNA is added to the cells, electroporation can be carried out immediately. It is not necessary to incubate DNA with cells. The maximum recommended volume of a DNA solution to be added is 2.5 µl. Addition of a large volume of DNA decreases transformation efficiency. 
  4. Contaminants such as salts and proteins can lower electroporation efficiency. Ideally, DNA for transformation should be purified and suspended in water or TE. Transformation efficiency is more than 10-fold lower for ligation mixtures than the control pUC19 plasmid due to the presence of ligase and salts. If used directly, ligation reactions should be heat-inactivated at 65°C for 20 min and then diluted 10-fold. For optimal results, spin columns (NEB #T1030) are recommended for cleanup of ligation reactions.
  5. Electroporation conditions vary with different cuvettes and electroporators. If you are using electroporators or cuvettes not specified in the protocol, you may need to optimize the electroporation conditions. Cuvettes with 1mm gap are recommended (e.g. BTX Model 610/613 and Bio-Rad #165-2089). Higher voltage is required for cuvettes with 2 mm gap. 
  6. Arcing may occur due to high concentration of salts or air bubbles.
  7. It is essential to add recovery medium to the cells immediately after electroporation. One minute delay can cause a 3-fold reduction in efficiency.

Application Features

DNA Effects on Transformation Efficiency and Colony Output: DNA Effects on Transformation Efficiency and Colony Output:
Electroporation efficiency remains extremely high up to about 10 ng of input DNA, then decreases at higher DNA concentrations.

Properties & Usage

Antibiotic for Plasmid Selection

Antibiotics for Plasmid Selection Working Concentration
Ampicillin 100 µg/ml
Carbenicillin 100 µg/ml
Kanamycin 30 µg/ml
Streptomycin 25 µg/ml
Tetracycline 15 µg/ml

Shipping Notes

  • Ships on dry ice

Antibiotic Resistance

  • none

Product Notes

  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.

Protocols, Manuals & Usage


  1. Electroporation Protocol (C2989)

Usage & Guidelines


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 [email protected] or fill out the Technical Support Form for appropriate document.)

Tools & Resources

Selection Charts

Web Tools

FAQs & Troubleshooting


  1. How should I calculate the Electrotransformation efficiency (C2989)?
  2. What are the solutions/recipes (C2989)?
  3. What are the strain properties (C2989)?
  4. How should I store SOC Outgrowth Medium? The SOC I received with my competent cells recommends storage at either room temperature or 4°C, however, when I purchase it as a stand alone product, it recommends storing it at 4°C. Which is better?
  5. How should fragments be prepared for assembly using NEBuilder HiFi?

Quality, Safety & Legal

Quality Assurance Statement

Quality Control tests are performed on each new lot of NEB product to meet the specifications designated for it. Specifications and individual lot data from the tests that are performed for this particular product can be found and downloaded on the Product Specification Sheet, Certificate of Analysis, data card or product manual. Further information regarding NEB product quality can be found here.


The Specification sheet is a document that includes the storage temperature, shelf life and the specifications designated for the product. The following file naming structure is used to name these document files: [Product Number]_[Size]_[Version]

Certificate Of Analysis

The Certificate of Analysis (COA) is a signed document that includes the storage temperature, expiration date and quality controls for an individual lot. The following file naming structure is used to name these document files: [Product Number]_[Size]_[Version]_[Lot Number]

Safety DataSheets

The following is a list of Safety Data Sheet (SDS) that apply to this product to help you use it safely.

Legal and Disclaimers

This product is covered by one or more patents, trademarks and/or copyrights owned or controlled by New England Biolabs, Inc (NEB).

While NEB develops and validates its products for various applications, the use of this product may require the buyer to obtain additional third party intellectual property rights for certain applications.

For more information about commercial rights, please contact NEB's Global Business Development team at [email protected]

This product is intended for research purposes only. This product is not intended to be used for therapeutic or diagnostic purposes in humans or animals.

New England Biolabs (NEB) is committed to practicing ethical science – we believe it is our job as researchers to ask the important questions that when answered will help preserve our quality of life and the world that we live in. However, this research should always be done in safe and ethical manner. Learn more.