Product Class: Polymerase

T4 DNA Polymerase

cloned at neb recombinant unique buffer 12 Degree incubation temp heat inactivation
Catalog #SizeConcentration
M0203S150 units3,000 units/ml
M0203L750 units3,000 units/ml



  • Extreme fidelity (6)
  • Gap filling (no strand displacement activity)
  • Best enzyme for creating blunt ends
  • Isolated from a recombinant source
T4 DNA Polymerase catalyzes the synthesis of DNA in the 5´→ 3´ direction and requires the presence of template and primer. This enzyme has a 3´→ 5´ exonuclease activity which is much more active than that found in DNA Polymerase I (E. coli).  Unlike E. coli DNA Polymerase I, T4 DNA Polymerase does not have a 5´→ 3´ exonuclease function.

Product Source

Purified from a strain of E. coli that carries the T4 DNA Polymerase gene.

Reagents Supplied

The following reagents are supplied with this product:

Store at (°C)Concentration
NEBuffer™ 2.1-2010X

Advantages and Features


  • 3´ overhang removal to form blunt ends (1,2).
  • 5´ overhang fill-in to form blunt ends (1,2).
  • Single strand deletion subcloning (3).
  • Second strand synthesis in site-directed mutagenesis (4).
  • Probe labeling using replacement synthesis (1,2).

Properties and Usage

Unit Definition

One unit is defined as the amount of enzyme that will incorporate 10 nmol of dNTP into acid insoluble material in 30 minutes at 37°C (5).

Reaction Conditions

1X NEBuffer 2.1
Incubate at 12°C

1X NEBuffer™ 2.1:
50 mM NaCl
10 mM Tris-HCl
10 mM MgCl2
100 μg/ml BSA
pH 7.9 @ 25°C

Storage Temperature


Storage Conditions

100 mM KPO4
1 mM DTT
50% Glycerol
pH 6.5 @ 25°C

Heat Inactivation

75°C for 20 min

Molecular Weight

Theoretical: 104000 daltons

5' - 3' Exonuclease


3' - 5' Exonuclease


Strand Displacement


Unit Assay Conditions

1X NEBuffer 2.1, 33 µM dNTPs including [3H]-dTTP, 70 µg/ml denatured herring sperm DNA.

Heat Inactivated


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. Further information regarding NEB product quality can be found here.
  • Endonuclease Activity (Nicking):
    The product is tested in a reaction containing a supercoiled DNA substrate. After incubation for 4 hours the percent converted to the nicked form is determined by agarose gel electrophoresis.

Supporting Documents

The Certificate of Analysis (COA) is a signed document that includes the storage temperature, expiration date and quality control's for an individual lot. The following file naming structure is used to name these document files: [Product Number]_[Size]_[Version]_[Lot Number]
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]
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. For fill-in reactions only: T4 DNA Polymerase can be used in NEBuffers 1.1, 2.1, 3.1 and CutSmart® Buffer as well as NEBuffers 1-4 and T4 DNA Ligase Reaction Buffer.
  2. For blunting reactions requiring removal of overhangs: T4 DNA Polymerase can be used in NEBuffers 1.1, 2.1, and CutSmart Buffer as well as NEBuffers 1, 2, and 4 and T4 DNA Ligase Reaction Buffer. NEBuffers 3.1 and 3 are not recommended when overhang removal is required.
  3. Optimal activity is observed in NEBuffer 2.1.
  4. Supplement with dNTPs.*
  5. BSA supplementation is recommended when using a buffer that does not already contain BSA.
  6. Incubate at temperature suggested for specific protocol.

    * Refer to specific protocol to determine recommended dNTP concentrations.


  1. Tabor, S. and Struhl, K. (1989). DNA-Dependent DNA Polymerases. In F. M. Ausebel, R. Brent, R. E. Kingston, D. D. Moore, J. G. Seidman, J. A. Smith and K. Struhl (Ed.), Current Protocols in Molecular Biology. 3.5.10-3.5.12. New York: John Wiley & Sons, Inc.
  2. Sambrook, J. et al. (1989). Molecular Cloning: A Laboratory Manual. (2nd ed.), 5.44-5.47. Cold Spring Harbor: Cold Spring Harbor Laboratory Press.
  3. Dale, R. et al. (1985). Plasmid. 13, 31-40.
  4. Kunkel, T.A. et al. (1987). Methods Enzymol.. 154, 367-382.
  5. Panet, A. et al. (1973). Biochemistry. 12, 5045-5050.
  1. Can T4 DNA Polymerase be used in other NEBuffers and CutSmart?
  2. Can T4 DNA Polymerase be used to blunt DNA?
  3. Can T4 DNA Polymerase be used to fill in 3' overhangs?
  4. Can T4 DNA Polymerase be used to remove 5' overhangs?
  5. Can T4 DNA Polymerase be heat inactivated?
  6. Are the nucleotides needed to remove a 3' overhang using T4 DNA Polymerase?
  7. What are the main causes of blunting reaction failure using T4 DNA Polymerase?
  8. Are NEB DNA Polymerases supplied with dNTPs?
  9. Can T4 DNA Polymerase be used in labeling reactions and partial fill in reactions?
  10. Is T4 DNA Polymerase active at room temperature?
  11. Is T4 DNA Polymerase the enzyme of choice for removing 3' overhangs and filling in 5' overhangs (3' recessed ends)?
  1. Protocol for blunting ends by 3’ overhang removal and 3’ recessed (5’ overhang) end fill-in using T4 DNA Polymerase (M0203)
Excess enzyme, temperatures above 12°C, or limited dNTP concentrations can cause excessive 3’ → 5’ exonuclease degradation, which eliminates blunt end formation.