Remove unwanted DNA to improve protein extraction efficiency.

Thermo Scientific DNase I removes unwanted DNA from cell lysates to improve protein extraction efficiency.

Deoxyribonuclease I (DNase I) is a single, glycosylated polypeptide that degrades unwanted single- and double-stranded DNA. The enzyme works by cleaving DNA into 5' phosphodinucleotide and small oligonucleotide fragments. DNase I is commonly added to cell lysis reagents to remove the viscosity caused by DNA content in bacterial cell lysates or removal of DNA templates from RNAs produced by in vitro transcription. Two grades of DNAse are offered, one sufficient for protein work and one that is useful for any application requiring the digestion of DNA in which it is crucial to avoid damage to RNA.

Highlights:

• Degrades and removes unwanted DNA from samples
• Cleaves both single-stranded and double-stranded DNA
• Compatible with Thermo Scientific Pierce Cell Lysis Reagents
• Reduces viscosity of bacterial lysates (protein extracts) to facilitate pipetting
• Supplied as 50% glycerol stocks in 10mM Tris•HCl, pH 7.5, 10mM CaCl2, 10mM MgCl2
• Available in two convenient formats: RNase tested to protect RNA (Part No. 89835) and convenient protein extraction grade (Part No. 90083)

Thermo Scientific Lysozyme improves protein extraction efficiency. To demonstrate the benefit of using lysozyme and DNase I to process bacterial extracts, the extractions of two different-sized, over-expressed proteins were compared. Cell pellets from 50mL culture of E. coli BL-21 over-expressing green fluorescent protein (GFP) or GST-Ral Binding Protein (GST-RalBP) were lysed using B-PER Reagent with and with out lysozyme and DNase I. The soluble fractions were separated from the pellets, and the two fractions were analyzed by SDS-PAGE. Although GFP (32 kDa) was extracted equally well in the absence or presence of enzyme, GST-RalBP (75 kDa) required lysozyme and DNase I to be efficiently solubilized.

General information about the use of DNase I:

• Calcium ions are required for activity of DNase I. Trace amounts of Ca++ may be present at high enough concentration for DNase I to be active, however use of EGTA or calcium-free buffers can reduce DNase I activity to undetectable levels.
• High levels (i.e., 100mM) of monovalent ions such as Na+ and K+ will decrease DNase I activity
• DNase I is inactivated by heating to 65°C for 10 minutes
• Kunitz unit: 1 Kunitz unit is the amount of enzyme required to cause an increase of 0.001 A260nm/min/mL at 25°C in 0.1M NaOAc, pH 5.0 due to degradation of highly polymerized DNA
• Degradation assay units: 1 unit is defined as the amount of enzyme required to completely degrade 1µg of plasmid DNA in the 10 minutes at 37°C in 10mM Tris•HCl, pH 7.5, 50mM MgCl2, 13mM CaCl2.

Specifications (Part No. 89835):

• Visual: Clear liquid
• Concentration: 5000 to 10,000 Units/mL
• Activity: ≥100,000 Units/mg protein
• RNase Contamination: 20 Units release <2% non-ethanol precipitable when incubated with 3H labeled Poly(A) RNA
• Functional Analysis: 1µL enzyme degrades <5% RNA but degrades 100% DNA.

Specifications (Part No. 90083):

• Visual: Clear, colorless liquid, free of insoluble material
• Units: ≥ 2500 units/mL
• Unit definition: 1 unit is defined as the amount of enzyme required to produce an increase in absorbance at 260nm of 0.001/min/mL at 25 degrees C of highly polymerized DNA.

References:

1. Campbell, V.W. and Jackson, D. A. (1980). The effect of divalent cations on the mode of action of DNase I. J. Biol. Chem. 255(8): 3726-35.
2. Krieg, P.A. and Melton, D.A. (1987). In vitro RNA synthesis with SP6 RNA polymerase. Methods in Enzymology, Recombinant DNA, ed by R. Wu. Part F. Vol 155: 397-415.
3. Melgar, E., and Goldthwait, D.A. (1968). Deoxyribonucleic acid nucleases II. The effects of metal on the mechanism of action of deoxyribonuclease I. J. Biol. Chem. 243(17): 4409-16.
4. Moore, S. (1981). Pancreatic DNase. In: The Enzymes. Boyer, P.D., eds. New York: Academic Press. pp. 281-96.
5. Pan, C.Q. and Lazarus, R.A. (1999). Ca2+-dependent activity of human DNase I and its hyperactive variants. Protein Sci. 8(9): 1780-8.
6. Sambrook, J., et al., (1989). Molecular Cloning: A Laboratory Manual, 2nd ed. New York: Cold Spring Harbor Laboratory Press. 10.6-10.12.
7. Tabor, S., et al. (1997). DNA-Dependent DNA Polymerases. In: Current Protocols in Molecular Biology. Ausubel et al., eds. Wiley & Sons Inc. 3.5.4-6.
8. Vitolo, J.M, et al. (1999). DNase I and hydroxyl radical characterization of chromatin complexes. In: Current Protocols in Molecular Biology, Ausubel et al., eds. Wiley & Sons Inc. 21.4.1-6.

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Inclusion Body Solubilization Reagent
Halt Protease Inhibitor Cocktail
Halt Phosphatase Inhibitor Cocktail
Lysozyme