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G3169 Sigma-Aldrich

GC5 Competent Cells

for generation of cDNA libraries and DNA plasmid production



Related Categories Competent Cells, Core Bioreagents, Life Science Reagents for Cloning, Research Essentials
grade   for molecular biology
form   suspension
shipped in   dry ice
storage temp.   −70°C


General description

GC5 are competent E. coli with a transformation efficiency of >1x109 cfu/μg when transformed with non-saturating amounts of pUC19 plasmid DNA. They are comparable to DH5α strain.


Suitable for recovery of high quality plasmid DNA and generation of cDNA libraries from plasmid-based vectors

GC5 chemically competent cells are comparable to the popular DH5α strain and carry recA1 and endA1 mutations that aid in plasmid stability and improved quality of prepared plasmid DNA. The GC5 strain allows for beta-galactosidase α-complementation for blue/white screening and is T1 bacteriophage resistant. GC5 Competent Cells are offered as a high efficiency grade for subcloning and generation of cDNA libraries.

Features and Benefits

• Ensures recovery of stable and high quality plasmid DNA.
• Renders protection to clonal stocks from T1 and T5 bacteriophage contamination
• Allows for β-galactosidase α-complementation for blue/white screening
• Guaranteed high transformation efficiency
• Convenient 50 μL aliquots


• GC5 chemically competent cells, 10 X 50 μL or 20 X 50 μL (G2669)
• pUC 19 control DNA (10 ng/μL), 10 μL (D2567)


GC5 contain mutations in recA1 and endA1 genes. These mutations aid in minimizing recombination and ensuring plasmid stability. This strain also contains tonA genotype that confers resistance to lytic bacteriophages such as T1 and T5.

Legal Information

DH5α is a trademark of Invitrogen Corp.

GC5 is a trademark of GeneChoice, Inc.

Safety & Documentation

Safety Information

NONH for all modes of transport


Certificate of Analysis (COA)

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Certificate of Origin (COO)

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Frequently Asked Questions

Which document(s) contains shelf-life or expiration date information for a given product?
If available for a given product, the recommended re-test date or the expiration date can be found on the Certificate of Analysis.
How do I get lot-specific information or a Certificate of Analysis?
The lot specific COA document can be found by entering the lot number above under the "Documents" section.
How do I find price and availability?
There are several ways to find pricing and availability for our products. Once you log onto our website, you will find the price and availability displayed on the product detail page. You can contact any of our Customer Sales and Service offices to receive a quote. USA customers: 1-800-325-3010 or view local office numbers.
What is the Department of Transportation shipping information for this product?
Transportation information can be found in Section 14 of the product's (M)SDS.To access the shipping information for this material, use the link on the product detail page for the product.
Are home-made competent cells as efficient at transformation as purchased cells?
They can be, depending on the technique used, the expected transformation efficiency and how the cells are handled.For special applications, competent cells prepared in-house using standard methods may not provide the efficiency you need.
Are all competent cells suitable for both plasmid production and protein expression?
No.Most strains of competent cells are suitable for producing plasmid DNA that will be used to transfect insect or mammalian cells for expression of the protein.The BL21 competent cell strains have special traits enabling protein expression in bacteria.
What are important considerations when performing bacterial transformation?
Things to consider when planning bacterial transformation:DNA impuritiesSource of DNAAmount of DNA usedStorage and handling of the competent cells
Can I store the competent cells in the -20C?
No.Competent cells should not be stored at -20C for any length of time.The cells suffer a dramatic drop in transformation efficiency when stored higher than -80C.
How should I thaw the competent cells?
Competent cells should be thawed on ice.The transformation efficiency is dependent on the proper handling of the cells (maintaining cold temperature until transformation).
Can I re-freeze the vial if I do not use the entire aliquot of competent cells?
Re-freezing competent cells will result in a decrease in their transformation efficiency.If the cells are frozen first in a dry ice / ethanol bath before placement in the -80C freezer, the loss will be about two-fold.If placed directly in the -80C freezer, the loss in transformation efficiency is about five to ten-fold.
Competent cells were left on ice overnight - can they still be used?
Competent cells left on ice, or allowed to come to room temperature slowly will suffer a dramatic loss in transformation efficiency.We recommend thawing a new aliquot of competent cells.
Can I express a recombinant protein that is toxic to the bacteria?
For expression of toxic recombinant proteins, select the BL21 strain containing the pLysS plasmid. These cells express low levels of lysozyme that will bind to T7 polymerase, and inhibit transcription.
What DNA purity do I need for use in transformation?
The DNA used should be high quality - free from phenol, proteins, detergents, and ethanol.Dissolve the DNA in sterile water or 0.5x TE buffer (5 mM Tris-HCl, 0.5 mM EDTA).
Can I grow more competent cells from the stock I purchased?
Generally, no, because the future generations of cells lose their competency.
My question is not addressed here, how can I contact Technical Service for assistance?
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Protocols & Articles


Bacterial Transformation Protocols

Transformation is a key process in molecular cloning, by which multiple copies of recombinant DNA molecules are produced. The ability to take up free, extracellular genetic material is the prerequisi...
Keywords: Antibiotics, Cloning, Detergents, Electrophoresis, Gel electrophoresis, Genetic, Mass spectrometry, Peptide synthesis, transformation

Selecting Correctly Expressing Recombinants

Blue / White colony screening is a strategy to quickly and easily distinguish between recombinant and non-recombinant colonies. It requires a special vector and a special strain of E. coli. It is par...
Keywords: AGE, Amplification, Antibiotics, Cell disruption, Centrifugation, Cloning, Degradations, Detergents, Diagnostic, Digestions, Electrophoresis, Gel electrophoresis, Molecular biology, Peptide synthesis, Phase transitions, Polymerase chain reaction, Precipitation, Purification, Sequencing, Transfection, transformation

Peer-Reviewed Papers


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