Promotional price valid on web orders only. Your contract pricing may differ. Interested in signing up for a dedicated account number?
Learn More

Thermo Scientific™ Terminal Deoxynucleotidyl Transferase (20 U/µL) Available on GSA/VA Contract for Federal Government customers only.

Terminal Deoxynucleotidyl Transferase (TdT) catalyzes the template-independent addition of deoxyribonucleotides to the 3'-OH terminus of DNA molecules.

Manufacturer:  Thermo Scientific™ EP0162

 View more versions of this product

Catalog No. FEREP0162

Add to cart



Terminal Deoxynucleotidyl Transferase (TdT), a template-independent DNA polymerase, catalyzes the repetitive addition of deoxyribonucleotides to the 3'-OH of oligodeoxyribonucleotides and single-stranded and double-stranded DNA. TdT requires an oligonucleotide of at least three nucleotides to serve as a primer. With RNA as template TdT shows variable performance which strongly depends upon the tertiary structure of acceptor RNA 3'-end and the nature of nucleotide. Generally, it is lower than using DNA as a template.

  • Incorporates modified nucleotides (e.g., fluorescein-, biotin-, aminoallyl-labeled nucleotides) Source: E. coli cells carrying a cloned gene encoding calf thymus terminal deoxynucleotidyl transferase
Quality Control:
  • The absence of endo-, exodeoxyribonucleases, phosphatases and ribonucleases confirmed by appropriate quality tests


  • E.coli cells carrying a cloned gene encoding calf thymus terminal deoxynucleotidyl transferase
Definition of Activity Unit:
  • One unit of the enzyme catalyzes the incorporation of 1nmol of deoxythymidylate into a polynucleotide fraction (adsorbed on DE-81) in 60 min. at 37°C
  • Enzyme activity is assayed in the following mixture:
    • 200mM potassium cacodylate (pH 7.2), 1mM CoCl2, 0.01% (v/v) Triton X-100, 10µM oligo(dT)10, 1mM dTTP and 0.4MBq/ml [3H]-dTTP
    Storage Buffer:
    • The enzyme is supplied in:100mM potassium acetate (pH 6.8), 2mM 2-mercaptoethanol, 0.01% (v/v) Triton X-100 and 50% (v/v) glycerol

    5X Reaction Buffer:

    • 1M potassium cacodylate, 125mM Tris, 0.05% (v/v) Triton X-100, 5mM CoCl2 (pH 7.2 at 25°C)

    Inhibition and Inactivation:

    • Inhibitors: metal chelators, ammonium, chloride, iodide, phosphate ions
    • Inactivated by heating at 70°C for 10 min. or by addition of EDTA

    Recommended for:

    Production of synthetic homo- and heteropolymers (1); Homopolymeric tailing of linear duplex DNA with any type of 3'-OH terminus (2, 3); Oligodeoxyribonucleotide and DNA labeling (2, 4-8); 5'-RACE (Rapid Amplification of cDNA Ends) (9); In situ localization of apoptosis (10)


    Due to the presence of CoCl2 the TdT Reaction Buffer is incompatible with downstream applications. It is necessary to remove CoCl2 from the reaction mixture by spin column or phenol/chloroform extraction and subsequent ethanol precipitation.

    This product(s) resides on a Fisher Scientific GSA or VA contract. If you are viewing this page as a nonregistered user, the price(s) displayed is List Price. To view your GSA or VA contract pricing, log in using your account number, or become a registered user by contacting one of our Customer Service teams. You can also view your contract price by searching for this item(s) on GSA Advantage. To place an order, contact Fisher Scientific Customer Service.



Terminal Deoxynucleotidyl Transferase
Provide Content Correction

We continue to work to improve your shopping experience and your feedback regarding this content is very important to us. Please use the form below to provide feedback related to the content on this product.

Product Title

By clicking Submit, you acknowledge that you may be contacted by Fisher Scientific in regards to the feedback you have provided in this form. We will not share your information for any other purposes. All contact information provided shall also be maintained in accordance with our Privacy Policy.

Cancel Submit