DNA sample storage: best practices after extraction

Purified DNA should be stored at –30°C to –15°C or –90°C to –65°C under slightly basic conditions (e.g., Tris×Cl, pH 8.0 or TE buffer; see tables 1 M Tris×Cl and TE buffer) because acidic conditions can cause hydrolysis of DNA. Avoid repeated freeze–thawing as this will lead to precipitates.

Diluted solutions of nucleic acids (e.g., dilution series used as standards) should be stored in aliquots (in siliconized tubes, where possible) and thawed once only. This avoids adsorption of nucleic acids to the tube walls, which would reduce the concentration of nucleic acids in solution.

1 M Tris·Cl

TE buffer

In the rapidly evolving world of molecular biology, maintaining the long-term stability and integrity of DNA is more important than ever. High-quality DNA is crucial for reproducible results in sensitive downstream applications.

Although DNA is a relatively stable molecule, the quality can decline over time, even at low temperatures. Degradation can be caused by a variety of factors:

• Hydrolysis: Water molecules can cleave the phosphodiester bonds in the DNA backbone, especially if the pH is acidic.
• Enzymatic degradation: DNAses or residual nucleases from the original sample or contaminating microorganisms can degrade DNA.
• Physical shearing: Repeated freeze–thaw cycles and vigorous mixing can shear DNA, particularly high-molecular-weight gDNA.
• Other factors: Adsorption to tube surfaces, evaporation or concentration loss

DNA storage time and temperature

The DNA storage temperature depends on a number of factors including the method used for storage and how long the DNA samples should be stored for.

DNA sample storage methods and temperatures

By following best practices, you can ensure the quality and integrity of your DNA samples, even when you need to store them for long periods.

• Use high-purity reagents and nuclease-free water/buffers.
• Always use nuclease-free tips, tubes and water.
• Keep work area clean to avoid nuclease contamination.
• Use a basic buffer for storage such as Tris-HCl or TE, pH ~8.
• Mix gently and avoid vortexing high-molecular-weight DNA.
• Minimize the number of freeze–thaw cycles.
• Divide the DNA solution into single-use aliquots.
• Store samples in a controlled environment, free from humidity, light and excessive heat.