Product Class: Competent Cell

T7 Express Crystal Competent E. coli (High Efficiency)

NEB does not add a dry ice surcharge to our competent cell shipments.
Catalog #SizeConcentration
C3022I6 x 0.2 ml/tube



  • Transformation efficiency: 0.6-1 x 109 cfu/μg pUC19 DNA
  • Enhanced BL21 derivative
  • Methionine auxotroph (metB1) designed for seleno-methionine labeling of proteins
  • Derivative of T7 Express with T7 RNA Polymerase on the chromosome under lac control
  • Deficient in proteases Lon and OmpT
  • Resistant to T1 phage (fhuA2)
  • Free of animal products
Chemically competent E. coli cells suitable for high efficiency transformation and protein expression for X-ray crystallography. This strain is ideal for seleno-methionine labeling of proteins.


  • T7 expression
  • Protease deficient
  • SeMet labeling for protein crystallography


fhuA2 lacZ::T7 gene1 [lon] ompT gal sulA11 R(mcr-73::miniTn10--TetS)2 [dcm] R(zgb-210::Tn10--TetS) endA1 metB1 Δ(mcrC-mrr)114::IS10

Advantages and Features


Crystal of NotI in complex with DNA substrate (Barry Stoddard and Abigail Lambert; Fred Hutchinson Cancer Research Center).
X-ray diffraction pattern of NotI.
Effect of heat shock time on T7 Express Crystal 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 T7 Express Crystal 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.

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. Lambert, A. R. et al. (2008). Structure. 16, 558-569.
  2. Sambrook, J. et al. (1989). Cold Spring Habor Laboratory Press. Molecular Cloning: A Laboratory Manual . (2nd ed.), (Appendix A.3)
  1. Why are there no colonies or no growth in liquid culture (C3022)?
  2. Why is there no protein visible on gel or no activity (C3022)?
  3. Why is induced protein insoluble (C3022)?
  4. What are the solutions/recipes (C3022)?
  5. What are the strain properties (C3022)?
  6. Can I store competent cells at -20°C instead of -80°C?
  7. What is the difference between NEB #C3022H and NEB #C3022I?
  8. What is the optimal heat shock time for this strain (NEB #C3022H and NEB #C3022I)?
  9. How long should I incubate DNA with cells on ice for this strain (NEB #C3022H and NEB #C3022I)?
  10. Which kind of transformation tubes should be used?
  11. What volume of DNA can be added into competent cells?
  12. What is the shelf life for this strain (NEB #C3022H and NEB #C3022I)?
  13. Are NEB's competent cells compatible with the "Plate and Go" protocol?
  1. High Efficiency Transformation Protocol (C3022)
  2. 5 Minute Transformation Protocol (C3022)
  3. Protocol for Expression Using T7 Express Crystal (C3022)
  4. Recommended media and expression conditions for T7 Express Crystal (C3022)
  5. Seleno-methionine Incorporation (C3022)

Application Notes