dsDNase HL (500 U)

From QIAGEN, dsDNase HL is a heat-labile recombinant endonuclease derived from a cold-water eukaryotic organism and recombinantly expressed in Pichia pastoris, with a molecular mass of 43.3 kDa. It shows high specific activity towards double-stranded DNA — at least 1000 times higher than towards single-stranded DNA — while leaving RNA undamaged, and hydrolyzes phosphodiester linkages to yield oligonucleotides carrying a 5′-phosphate and a 3′-hydroxyl group.

The enzyme is supplied in a storage buffer of 20 mM Tris-HCl (pH 8.0), 20 mM NaCl, 2 mM MgCl2, 1 mM CaCl2 and 50% (v/v) glycerol, at ≥2 U/µL. One unit (Kunitz) is defined as the amount of enzyme causing an absorbance increase at 260 nm of 1.0 in 30 minutes at 37°C in 50 mM Tris-HCl buffer, pH 8.0 (25°C), supplemented with 5 mM MgCl2, 0.1 mg/mL BSA and 0.5 mg/mL herring sperm DNA as substrate. It operates across a pH range of 6.0–10.0 (optimum 7.0–8.0) and temperature range of 4–47°C (optimum 10–47°C), requiring Mg2+ ions (optimal 2–4 mM) and being further stimulated by Ca2+ ions (optimal 1–5 mM). It is rapidly and irreversibly inactivated by incubation at 52°C for 15 minutes in the presence of 1–10 mM DTT or TCEP, with no need to physically remove it from the reaction before downstream processing.

Typical applications include digestion of double-stranded DNA (plasmid or genomic), rapid purification of RNA and protein samples free of contaminating DNA, decontamination of PCR, qPCR master mixes and other diagnostic reagents, and degradation of DNA template in transcription reactions. The enzyme is produced using animal origin-free materials, and quality testing reports no detectable RNase or proteolytic activity.