Intact Genomics chemically competent DL39 (DE3) E. coli cells are specific for transformation and protein expression in order to uniformly and specifically label :e.g. phenylalanine or leucine residues.  DL39 (DE3) can also be used to reduce NMR cross-labeling via transaminase activity for valine, leucine, isoleucine, aspartate, phenylalanine, tyrosine and tryptophan residues.


Competent cell type:                Chemically competent
Derivative of:                             DL39
Species:                                     E. coli
Format:                                       Tubes
Transformation efficiency:       ≥1 x 107 cfu/µg pUC19DNA
Blue/white screening:               Yes
Shipping condition:                   Dry ice

Reagents Needed for One Reaction

DL39 (DE3) chemically competent cells: 50 µl
DNA (or pUC19 Control, 10 pg/µl):  1 µl
Recovery medium:   1 ml


DL39 (DE3) competent cells: -80 ºC
pUC19 control DNA: -20 ºC
Recovery medium:    4 ºC

Genomic Features

DL39 (DE3) chemically competent cells have the following features:

  • Deficient in the aromatic (TyrB), branched-chain (JIvE), and aspartate (AspC) transaminases.
  • Modified to contain the T7 expression system


F-, λ-, aspC13, fnr-25, rph-1, ilvE12, tyrB507,λDE3


Quality Control

Transformation efficiency is tested by using the pUC19 control DNA supplied with the kit and using the high efficiency transformation protocol listed below. Transformation efficiency should be ≥1×108 CFU/µg pUC19 DNA. Untransformed cells are tested for appropriate antibiotic sensitivity.

General Guidelines

Follow these guidelines when using DL39 (DE3)chemically competent cells.

  • Handle competent cells gently as they are highly sensitive to changes in temperature or mechanical lysis caused by pipetting.
  • Thaw competent cells on ice, and transform cells immediately following thawing. After adding DNA, mix by tapping the tube gently. Do not mix cells by pipetting or vortexing. 

Calculation of Transformation Efficiency
Transformation Efficiency (TE) is defined as the number of colony forming units (cfu) produced by transforming 1µg of plasmid into a given volume of competent cells.

TE = Colonies/µg/Dilution

Transform 1 µl of (10 pg/µl) pUC19 control plasmid into 50 µl of cells, add 950 µl of Recovery Medium. Dilute 10 µl of this in 990 µl of Recovery Medium and plate 50 µl. Count the colonies on the plate the next day. If you count 100 colonies, the TE is calculated as follows:

Colonies = 100

µg of DNA = 0.00001

Dilution = 50/1000 x 10/1000 = 0.0005

TE = 100/.00001/.0005 = 2.0×10101061-12 1061-24