Klenow Fragment (10 U/μL)

Thermo Scientific DNA Polymerase I possesses 5′?3′ DNA synthesis activity, 3′?5′ exonuclease (proofreading) activity, and 5′?3′ exonuclease activity. Klenow Fragment is the large fragment of DNA polymerase I. It exhibits 5′?3′ polymerase activity and 3′?5′ exonuclease (proofreading) activity, but lacks 5′?3′ exonuclease activity. Klenow Fragment, exo-, is also the large fragment of DNA polymerase I. It exhibits 5′?3′ polymerase activity, but lacks the 3′?5′ and 5′?3′ exonuclease activities.

Klenow can be used to "fill in" 5' overhangs of double-stranded DNA fragments using common restriction endonuclease buffers. We recommend REact 2 buffer (1X concentration is 50 mM Tris-HCl pH 8, 50 mM NaCl, 10 mM MgCl2) , but other buffers will also work.

Fill-in Reaction Conditions:

1. Dilute Large Fragment of DNA Polymerase I to 0.5 U/µL with Klenow Dilution Buffer.
2. To a 1.5-mL microcentrifuge tube on ice, add: 10X REact 2 Buffer - 3 µL, 0.5 mM dATP - 1 µL, 0.5 mM dCTP - 1 µL, 0.5 mM dGTP - 1 µL, 0.5 mM dTTP - 1 µL, DNA 0.5-1 µg, Large fragment of DNA Polymerase I - 1 µL, Autoclaved distilled water to 30 µL.
3. Mix gently and centrifuge briefly to bring the contents to the bottom of the tube.
4. Incubate at room temperature for 10-15 minutes or 20 minutes on ice.
5. Terminate fill-in reaction by phenol extraction.

To label the DNA fragment, use 1-2 µL of [alpha-³²P]dNTP (400 Ci/mmol, 10 mCi/mL) (24-48 pmoles) instead of the corresponding cold dNTP.

Note: Thermo Fisher Scientific also offers an Exo minus Klenow, which is provided with its own buffers.