DNase I is a versatile enzyme that non-specifically cleaves DNA to release 5'-phosphorylated di-, tri-, and oligonucleotide products (see also "DNase I Demystified"). The enzyme is a widely used research tool for a number of reactions involving DNA manipulation. Some of its uses include:

1. Degradation of contaminating DNA after RNA isolation,
2. "Clean-up" of RNA prior to RT-PCR and after in vitro transcription,
3. Identification of protein binding sequences on DNA (DNase I footprinting),
4. Prevention of clumping when handling cultured cells, and
5. Creation of a fragmented library of DNA sequences for in vitro recombination reactions.

DNase I Vendor Comparisons

Ambion recently tested DNase I preparations from many different commercial sources. A single lot of enzyme from each vendor was tested. The enzymes were used the within 24 hours of arrival to ensure that there was no loss of activity due to extended storage. The enzymes were tested for both purity and specific activity. Specific activity was measured using a Kunitz Unit definition which is defined as: The amount of DNase I added to 1 mg/ml salmon sperm DNA that causes an increase of 0.001 absorbance units per minute. Furthermore, we also tested the different DNase I preparations for RNase and protease activity using Ambion's standard inhouse Quality Control (QC) assays for these contaminants. The QC assays were performed on all the DNase I preparations at the same protein concentration.

Table 1, shown below, displays the specific activity data as measured by Kunitz units and the results of the QC assays, for Ambion's DNase I and DNase I from other vendors:

Each lot of Ambion's DNase I is rigorously tested for RNase and protease contamination. For monitoring RNase contamination, the DNase I is incubated with a radiolabeled RNA probe for 16 to 18 hours. After incubation, the probe(s) is run on a denaturing gel to assess the level of contamination as manifested by probe degradation. Protease contamination is measured using a spectrophotometric assay by incubating the DNase I with a peptide substrate that when cleaved produces light. Ambion's DNase I should perform well in any application that has stringent requirements for the absence of contaminating ribonuclease and/or protease. A 10X Reaction Buffer is included with the DNase I.

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DNase I Demystified

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Ordering Information