Preparation of DNase-free Bovine Pancreatic RNase A

Overview

  • Bovine pancreatic RNase (RNase A) is an endoribonuclease. It specifically degrades single-stranded RNA at C and U residues at higher salt concentrations (0.3 M or higher NaCl concentrations).
  • It cleaves single-stranded as well as double-stranded RNA and also RNA strand in RNA-DNA hybrids at low salt concentrations (0 to 100 mM NaCl).
  • It is active under a wide range of reaction conditions.
  • Unlike DNases, RNase A is quite stable to heat. Boiling RNase A solution for 5 – 10 minutes usually eliminates residual DNases activity without compromising RNases A activity. This preparation of RNases A is sufficient for most molecular biology work including the preparation of RNA free plasmid DNA.

Requirements

Reagents
> Bovine pancreatic RNase A
> 1M Tris.Cl, pH 7.5
> Milli Q/Deionized water

Equipment and disposables
> 15-ml screw-cap graduated polypropylene centrifuge tube
> Boiling water bath

Composition
> 10 mg/ml pancreatic RNase
> 10 mM Tris.Cl, pH 7.5

Objective
Preparation of 10 ml of 10 mg/ml DNase free bovine pancreatic RNase A

Prior to start:
Set the water bath for boiling.

Protocol

Step 1: To prepare, 10 ml of bovine pancreatic RNase A solution, weigh out 100 mg bovine pancreatic RNase A, and transfer it to a 15-ml screw-cap graduated polypropylene centrifuge tube. Add 7 ml Milli Q/Deionized water and 100 µl of 1M Tris.Cl (pH 7.5). Mix by inverting the tube several times until all RNase A is dissolved completely.

Tip:
We recommend using disposable DNases-free 15-ml screw-cap graduated polypropylene centrifuge tubes. Since these tubes have milliliter marks, you can adjust the solution volume without transferring the solution to the measuring cylinder. These tubes are heat resistant, inert, and can be centrifuged to remove any precipitate from the solution.

Precaution:
Avoid frothing while mixing the ingredients.

Step 2: Adjust the volume to 10 ml with Milli Q/Deionized water.

Tip:
We recommend you giving a short spin to the 15 ml tube just before adjusting the volume. Short spin will help to collect all liquid drops which are adhered to the sides and to the lid of the tube.

Step 3: Keep the centrifuge tube in a boiling water bath for 5 – 10 minutes.

Tip:
Shake the tube occasionally during incubation in the water bath. This will help to transfer heat to all parts of the solution.

Precaution:
Don’t directly boil the RNase solution on the hot plate. This may lead to the precipitation of proteins.

Step 4: Cool the solution to room temperature. Centrifuge at high speed (5,000 rpm) to remove the precipitate.

Storage
Make 1 ml aliquots and store at -20°C. RNases A is very stable and can be stored at -20°C/-80°C for 1 year.

Application
>Plasmid DNA isolation
> Preparation of RNA-free DNA

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