Thermo Scientific™

Phusion U Hot Start DNA Polymerase

Catalog number:  F555L

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Thermo Scientific Phusion U DNA polymerase is a novel engineered high fidelity enzyme developed using fusion technology. Due to a proprietary mutation in the so called dUTP binding pocket of Phusion, Phusion U overcomes an important limitation of proofreading enzymes - it is able to incorporate dUTP and read through uracil present in DNA templates.

In addition to uracil usage possibility, Phusion U features all the superior properties of other Phusion DNA Polymerases - great accuracy, speed, ability to amplify long amplicons up to 20 kb and a high specificity with Affibody based hot start. These features make Phusion U Hot Start DNA Polymerase an excellent choice for such important applications as amplification of bisulphite-converted or damaged DNA as well as use of carryover contamination control.

Phusion U Hot Start DNA Polymerase is also available in the Master Mix and Green formats. Phusion U Hot Start PCR Master Mix (F-533S and F-533L) is convenient 2X mix designed to minimize the number of pipetting steps. Only template and primers need to be added by the user. Phusion U Green format (F-556S and F-556L) is a combination of Phusion U Hot Start DNA Polymerase and 5X Phusion Green Buffers. The buffers include a density reagent and two tracking dyes for direct loading of PCR products on a gel. The colored buffer does not interfere with Phusion U performance and is compatible with downstream applications such as DNA sequencing, ligation and restriction digestion.


Accuracy—high fidelity DNA polymerase (25x Taq)
Uracil-tolerance —engineered to incorporate dUTP and amplify uracil containing templates
Specificity—hot start for reduced nonspecific amplification and primer degradation
Speed —short extension times (15-30 s/kb)


• Amplification of bisulphite-converted DNA
• Amplification of damaged or aged DNA
• Carry-over contamination control
• Uracil-excision based (USER) cloning methods

Using Phusion DNA Polymerases
Annealing rules for Phusion DNA Polymerases are different from many common DNA polymerases (such as Taq DNA polymerases). For optimal results, use our Tm calculator at

For Research Use Only. Not for use in diagnostic procedures.


Hot Start: Built-In Hot Start
Quantity: 500 Units
Fidelity (vs. Taq): 25 X
GC-Rich PCR Performance: High
Overhang: Blunt
Polymerase: Phusion U Hot Start DNA Polymerase
Product Line: Phusion
Product Type Specs: Hot Start DNA Polymerase
Reaction Format: Standalone
Reaction Speed: Fast
Size (Final Product): 20 kb

Contents & storage

• Phusion U Hot Start DNA Polymerase, 2 U/µL
• 5X Phusion HF Buffer
• 5X Phusion GC Buffer
Both Phusion HF Buffer and Phusion GC Buffer provide 1.5 mM MgCl2 in the final 1X concentration.

Store at -20°C.