Tips on using dried oligonucleotides |
Below you will find a few tips on how best to handle oligonucleotides when you receive them in dried form, the best way to solubilise them and other things you might keep in account. This is only meant to be an overview. Should you have further questions or problems, feel free to contact us and we’ll be glad to assist you.
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You receive the oligonucleotides in dried form. Stability tests have shown that oligonucleotides in dried form remain stable longest, which is why you should not solubilise them until shortly before use. We strongly recommend that oligonucleotides be solubilised in (sterile and deionised) water without any buffer. The oligonucleotide concentration you will have after solubilising in the stated amount of water can be seen on the caps as well as the shipping order.
For example, the cap says 120 nmol. Solubilising the contents in 1 ml distilled water yields a 120 µM solution (equal to 120 nmol/ml). Solubilising it in 0.5 ml distilled water yields a 240 µM solution (equal to 240 nmol/ml). Once the oligonucleotides are in solution, they have to be stored at -20°C. Moreover, it is advisable to aliquot the oligonucleotides and then only though the amount needed for the experiment.
Oligonucleotides in solubilised form will not remain stable forever, not even when stored at -20°C. This is especially true for oligonucleotides bearing modifications and RNA molecules.
Tips for DNA oligonucleotides |
From time to time, a DNA oligonucleotide (in ordered modifications) does not immediately solubilise. In this case, the following methods should help: Briefly warm the oligonucleotide to about 55°C. Add a bit of ammonia. The ammonia will have to be removed again in a vacuum concentrator, because it can be problematic in various applications. Shortly place the receptacle in an ultrasound bath.
Tips for RNA oligonucleotides |
RNA is quite sensitive to changes in pH, as well as temperatures above 0°C. Distilled and deionised water should always be used for the solution. Tris-HCl buffer is not suitable for solubilising RNA nucleotides!
Tips on phosphorothioates |
After a period of time, oxidation can be evidenced on the phosphorus of phosphorothioates, whereby the P=S link is exchanged for a P=O link. This ends the modification. Phosphorothioates should be stored at -20 °C as long as possible. In dried form, oligonucleotides remain usable under these conditions for up to 6 months.
Tips on colour modifications |
Colour modifications, such as fluorescein marking, are sensitive to light rays (and not only in solution). Such oligonucleotides should thus be stored cool and away from light. One option is to wrap the container in aluminium foil.
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