Klenow (3'-5' exo-) (low conc) (10000 U)

This mesophilic DNA polymerase from QIAGEN is the large fragment of E. coli DNA Polymerase I rendered deficient in both proofreading (3'→5') and nick-translation (5'→3') exonuclease activities. The enzyme is expressed as a truncated product of the E. coli PolA gene and carries the D355A and E357A mutations. It displays moderate strand displacement activity during DNA synthesis, making it well suited for DNA labeling workflows and dA/dT (A-tailing) reactions that enable direct ligation of next-generation sequencing adapters. The absence of 3'→5' exonuclease activity prevents the enzyme from removing added A/T tails, and supports efficient, stable end-labeling of DNA fragments with 5' overhangs using labeled nucleotides.

Specific activity is 10,000 U/mg, with physical purity assessed at >99% by SDS-PAGE with silver staining. One unit is defined as the amount of polymerase required to convert 10 nmol of dNTPs into acid-insoluble material in 30 minutes at 37°C. Quality control specifications confirm <10% release of single-stranded exonuclease activity, <1% release of double-stranded exonuclease activity, no conversion in double-stranded endonuclease assays, <10 copies of E. coli genomic DNA, and <20 U/mL uracil DNA glycosylase (UDG) contamination, each tested at 500 U. The enzyme is supplied at a concentration of 5,000 U/mL in 20 mM Tris-HCl, 1 mM DTT, 0.1 mM EDTA, 50% glycerol (pH 7.5 at 25°C), accompanied by 10X Blue Buffer containing 500 mM NaCl, 100 mM Tris-HCl, 100 mM MgCl₂, and 10 mM DTT (pH 7.9 at 25°C). The product is intended for in vitro use only. Recommended storage is -25°C to -15°C, and the molecular weight of the protein is 68,100 Daltons.