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  • Phusion® High-Fidelity DNA Polymerase


    High-Fidelity DNA Polymerases are important for applications in which the DNA sequence needs to be correct after amplification. Manufactured and quality-controlled at New England Biolabs, Thermo Scientific® Phusion High-Fidelity DNA Polymerase offers both high fidelity and robust performance, and thus can be used for all PCR applications. Its unique structure, a novel Pyrococcus-like enzyme fused with a processivity-enhancing domain, increases fidelity and speed. Phusion DNA Polymerase is an ideal choice for cloning and can be used for long or difficult amplicons. With an error rate > 50-fold lower than that of Taq DNA Polymerase and 6-fold lower than that of Pyrococcus furiosus DNA Polymerase (1), Phusion is one of the most accurate thermostable polymerases available. Phusion DNA Polymerase possesses 5´→ 3´ polymerase activity, 3´→ 5´ exonuclease activity and will generate blunt-ended products.

    Phusion DNA Polymerase is supplied with standard 5X Phusion HF Buffer, as well as 5X Phusion GC Buffer, which can be used for complex or GC-rich templates. Each of these buffers contains MgCl2 (1.5 mM at the final [1X] reaction concentration). Reactions can also be optimized using the provided DMSO or MgCl2 solutions.

    Fidelity assays were performed using a lacI-based method modified from Frey & Suppman, 1995.
    A 3.8 kb fragment was amplified from 50 ng of Jurkat gDNA using different polymerases. Reactions were carried out according to the manufacturer's recommended conditions. Extension times are indicated (in minutes). Ladder L is a 1 kb DNA Ladder (NEB# N3232).

    Product Source

    An E. coli strain that carries the Phusion DNA Polymerase gene.

    Reagents Supplied

    The following reagents are supplied with this product:

    Store at (°C)Concentration
    MgCl2 solution50 mM
    Phusion® HF Buffer-205X
    Phusion® GC Buffer Pack-205X

    Advantages and Features


    • Robust Reactions – Maximal success with minimal optimization
    • Extreme Fidelity – >50X greater than Taq.
    • High Speed – Dramatically reduced extension times (10X faster than Pfu)
    • High Yield – Increased product yield using minimal amount of enzyme
    • Versatile – Can be used for routine PCR as well as long or difficult templates


    • PCR
    • Cloning
    • Long or Difficult Amplification
    • High-Throughput PCR

    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 74°C.

    Storage Temperature


    Storage Conditions

    20 mM Tris-HCl
    100 mM KCl
    1 mM DTT
    0.1 mM EDTA
    200 μg/ml BSA
    50% Glycerol
    1X stabilizers
    pH 7.4 @ 25°C

    Heat Inactivation


    5' - 3' Exonuclease


    3' - 5' Exonuclease


    Unit Assay Conditions

    25 mM TAPS-HCl (pH 9.3 @ 25°C), 50 mM KCl, 2 mM MgCl2, 1 mM β-mercaptoethanol, 200 µM dNTPs including [3H]-dTTP and 400 µg/ml activated Calf Thymus DNA. 

    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.
    • 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.
    • PCR Amplification (DNA Polymerase):

      The polymerase master mix is tested in a polymerase chain reaction (PCR) using a control template and specific primers, resulting in the expected product.


    1. Frey, B. and Suppman, B. (1995). BioChemica. 2, 34-35.
    2. Chester, N. and Marshak, D.R. (1993). Analytical Biochemistry. 209, 284-290.

    Supporting Documents

    Material Safety Datasheets

    The following is a list of Material Safety Data Sheets (MSDS) that apply to this product to help you use it safely. The following file naming structure is used to name these document files: [Product Name] MSDS. For international versions please contact us at info@neb.com.


    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 info@neb.com or fill out the Technical Support Form for appropriate document.
    1. What has changed?
    2. Have the formulations or any other characteristics of these products changed now that they are manufactured by NEB?
    3. Which thermophilic DNA polymerase should I use?
    4. Can I continue to use the same reaction conditions if I use Phusion® products with the new product numbers?
    5. Are the prices and sizes of these products the same now that they are manufactured by NEB?
    6. Are the DNA fragments produced by Phusion® High-Fidelity DNA Polymerase blunt-ended or do they have the single-base 3´ overhang that Taq DNA Polymerase yields?
    7. My template is GC-rich or supercoiled. How can I optimize my product yield using Phusion® High-Fidelity DNA Polymerase?
    8. What are the advantages of using Phusion® Hot Start Flex DNA Polymerase?
    9. What is the error rate of Phusion® High-Fidelity DNA Polymerase?
    10. I am having trouble amplifying a template that is longer than 5kb. How can I optimize my product yield using Phusion® High-Fidelity DNA Polymerase?
    11. Why do I see no product or low yield on an agarose gel after a PCR using Phusion® High-Fidelity DNA Polymerase?
    12. Why are there high molecular weight smears or DNA in the wells of an agarose gel after a PCR using Phusion® High-Fidelity DNA Polymerase?
    13. Will Phusion® High-Fidelity DNA Polymerase incorporate dUTPs?
    14. Why are there low molecular weight discrete bands on an agarose gel after a PCR using Phusion® High-Fidelity DNA Polymerase?
    15. I'd like to clone a fragment amplified with Phusion® High-Fidelity DNA Polymerase. Do I have to blunt-end clone?
    16. I see foaming when my Phusion® High-Fidelity DNA Polymerase-amplified PCR products are spotted on microarray slides.
    17. What should my primer concentration be when using Phusion® High-Fidelity DNA Polymerase/Phusion® High-Fidelity PCR Master Mix?
    18. I am competing in the iGEM competition. Do you have any products that I should consider purchasing from NEB?
    1. PCR Protocol for Phusion® High-Fidelity DNA Polymerase (M0530)

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    Phusion has different annealing temperature requirements than most PCR enzymes. Please check out NEB's Tm Calculator to help you determine your optimal Phusion annealing temperature.