Ambion DNase I (RNase-free) (E.C. 3.1.21.1) is a nonspecific endonuclease that degrades double- and single-stranded DNA and chromatin. It functions by hydrolyzing phosphodiester linkages, producing mono and oligonucleotides with a 5'-phosphate and a 3'-hydroxyl group. RNase-free DNase I is of the highest purity available and is recommended to degrade DNA in the presence of RNA when the absence of RNase is critical to maintain the integrity of the RNA. For example, DNase I is frequently used to remove template DNA following in vitro transcription, and to remove contaminating DNA in total RNA preparations (especially those from transfected cells that may contain plasmid DNA), used for ribonuclease protection assays, cDNA library contraction, and RT-PCR. DNase I requires bivalent cations (Mg²⁺ and Ca²⁺ at approximately 5 mM and 0.5 mM, respectively) for maximal activity, and has a pH optimum of 7.8.

RNase-free DNase I outperforms the competition
A research report in BioTechniques (Matthews et al., 32: 1412-1417, 2002) compared RNase contamination in DNase I preparations from Sigma, Roche, Applied Science, Qiagen, and Ambion. The results revealed that “...with the exception of Ambion™'s RNase-free DNase I, the integrity of cRNA from in vitro transcription reactions was compromised and was still contaminated with DNA. Ambion™'s DNase was used for the remaining experiments requiring DNase digestion...”. Ambion™ DNase I is tested for contaminating RNase and protease activity. Functionality is determined by digestion of human genomic DNA followed by quantitative real-time PCR to detect undigested DNA.

Unit definition
One unit is the amount of enzyme required to completely degrade 1 μg DNA in 10 min at 37°C, and is equivalent to 0.04 Kunitz units.

Accessory products
For an alternative to bovine DNase I, please consider Recombinant DNase I (Cat. No. AM2235). For a more-active, salt-tolerant DNase, please see the TURBO™ DNase products (Cat. Nos. AM2239 and AM2238).