How to store DNA and RNA oligonucleotides to enhance your success in all your experiments?
Isolated and purified RNA is intrinsically labile. The ubiquity of ribonuclease (RNase) activity further complicates RNA oligonucleotides' handling. The proper storage of oligonucleotides is crucial for their stability. Starting with precise amounts of DNA and RNA in the solution ensures reliable results during all downstream procedures. The correct storage conditions for RNA samples are often hotly discussed. Improper storage, for a few hours or longer, can profoundly affect experimental results.
For RNA oligonucleotides, to prevent repeated freezing and thawing, the most prudent approach is to determine the concentration first, followed by storing the remaining RNA in suitable aliquots at -80 ºC.
Storage of DNA oligonucleotides:
The purified oligonucleotides' stability depends on the nature of the storage medium and temperature. When correctly stored a -20 ºC, frozen oligonucleotides can remain stable for up to two years or longer, as a dry powder and in both TE buffer and nuclease-free water. Most oligonucleotides are stable for more than 60 weeks when stored dry at 4 ºC or in DNase and RNase-free medium, including TE buffer and water.
However, the best practice is the storage of oligonucleotides in a freezer in the dark at -20 ºC either in nuclease-free TE buffer or water for up to 2 years.
Storage in increased temperatures or room temperature:
Storing oligonucleotides at 37°C/98°F is possible for several weeks. However, the selected medium will influence their stability. Oligonucleotides are generally most stable when stored in TE buffer at pH 8.0. Any moisture present in dry oligonucleotides, even small traces, can cause damage to the oligonucleotides.
Reconstitution and resuspension of oligonucleotides:
Bio-Synthesis Inc. provides oligonucleotides as a lyophilized white powder. However, per special request, a normalized RNA solution is provided for an additional fee.
To reconstitute oligonucleotides, follow the next steps:
1. Centrifuge at 10,000g for 15 seconds at room temperature (RT).
2. Add the desired volume of filtered, sterile TE buffer (10 mM Tris-HCL pH 8.0, 1 mM EDTA) or DNase-free and RNAase-free H2O.
3. Allow rehydrating for 10-15 minutes at room temperature.
4. Vortex for 5 seconds, then centrifuge at 10,000g for 15 seconds at room temperature.
5. Proceed with your downstream application.
Shipping of oligonucleotides:
Bio-Synthesis Inc. ships oligonucleotides as a lyophilized dry powder, usually overnight, to allow flexibility to our customers. The shipping time will not be detrimental to the stability of dry oligonucleotides since dry oligonucleotides remain stable for up to 25 weeks when stored at 37°C (98°F). Most oligonucleotides will remain functional for multiple weeks at this higher temperature when stored in water and storage media.
Freezing and thawing of oligonucleotides:
During some experiments, oligonucleotides may need to be repeatedly frozen and thawed. If correctly dissolved in nuclease-free media, up to 30 freeze-thawing cycles may have no significant impact on the stability of an oligonucleotide.
Modified oligonucleotides:
Most modified oligonucleotides will have similar stability characteristics as unmodified oligonucleotides. However, heavily modified oligonucleotides will be significantly more stable, especially to nuclease-depended degradation.
However, it is most prudent to store modified oligonucleotides like unmodified oligonucleotides.
RNA oligonucleotides are less stable:
RNA oligonucleotides are inherently less stable than DNA. Also, the ubiquity of ribonuclease (RNase) activity complicates the handling of RNA oligonucleotides further. RNases are present in human saliva, mucus, sweat, dead hair, and skin cells and are also more prevalent in laboratories than DNases. Therefore, avoiding RNase contamination is critical to maintaining RNA stability. Even minor exposure to RNases will cause RNA degradation. We recommend, for long-term storage storing RNA as an ethanol precipitate at -80°C.
Reference
Farrell, R.E.; RNA Methodologies 5th Edition. Academic Press 2017.
Roskams, J. and Rogers, L.; Lab Ref. A handbook of recipes, reagents, and other reference tools fo use at the bench. Cold Spring Harbor Laboratory Press. 2002.
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Bio-Synthesis provides a full spectrum of oligonucleotide and peptide synthesis including bio-conjugation services as well as high quality custom oligonucleotide modification services, back-bone modifications, conjugation to fatty acids and lipids, cholesterol, tocopherol, peptides as well as biotinylation by direct solid-phase chemical synthesis or enzyme-assisted approaches to obtain artificially modified oligonucleotides, such as BNA antisense oligonucleotides, mRNAs or siRNAs, containing a natural or modified backbone, as well as base, sugar and internucleotide linkages.
Bio-Synthesis also provides biotinylated mRNA and long circular oligonucleotides.
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