NAsafe: RNA & DNA Preservation Medium

NAsafe is a high-salt, low-pH preservation medium designed to inactivate proteins (including nucleases) via salting-out. It supports short-term room-temperature storage and long-term freezing—when used correctly.

Formulation (1 L)

  • 4 M (NH4)2SO4
  • 10 mM EDTA
  • 0.1 M MES, pH 4.6
Store at room temperature (typical stability: 6 months).
Handling & safety
NAsafe is highly concentrated salt and mildly acidic. Avoid contact with eyes/skin, use gloves, and wipe spills with water. Follow your institutional safety guidance for chemical handling and waste.
Important limitation
Use NAsafe with fresh tissue only. Do not freeze tissue before immersion.

Preparation of NAsafe (1 L)

  1. Combine 40 ml of 0.5 M EDTA and 19.5 g MES free acid.
  2. Add 528 g ammonium sulfate.
  3. Dissolve in Milli-Q water and bring final volume to 1 L.
  4. Stir on a hot plate stirrer on low heat until ammonium sulfate is fully dissolved.
  5. Transfer to a screw-top bottle. Store at room temperature or refrigerated.
If precipitation is observed
Warm to ~37°C and agitate until fully redissolved, then return to storage.
Storage
Room temperature storage is acceptable; typical stability is 6 months if properly stored.

Guidelines for use

  • Use with fresh tissue only; do not freeze before immersion.
  • Cut large tissues to ≤ 0.5 cm in any dimension before immersion.
  • Immerse tissue in 5–10 volumes of NAsafe.
  • Room temperature storage is typically acceptable for up to 1 week without compromising RNA quality.
  • For long-term storage at −20°C or −80°C: keep at 4°C overnight to allow penetration, remove supernatant, then freeze.
  • RNase inactivation can be reversible: do not rinse with NAsafe. Instead, blot tissues or pellet cells to remove excess solution.
Expected performance
After 2 weeks at ~25°C, RNA may show mild degradation. This can still be suitable for RT-PCR and related assays, but is less optimal for applications requiring very high integrity.

Quick checklist

  • Fresh sample
  • Small tissue pieces
  • High volume ratio
  • Overnight at 4°C before freezing
  • Blot/pellet; do not rinse

Why it works (brief)

NAsafe relies on a strongly kosmotropic environment (high sulfate) and low pH to promote protein precipitation (salting-out) and reduce enzymatic activity. This principle is related to the Hofmeister (lyotropic) series, which ranks ions by their effects on protein solubility and water structure.

Cations (stronger salting-out → weaker): NH4+ > Na+ > K+ > Li+ …
Anions (stronger salting-out → weaker): OH− > SO42− > HPO42− > F− …

For background on the Hofmeister series and ion-specific effects, see the referenced review. doi:10.1021/cr200271j

Related protocols

DNA extraction
RNA extraction
Electrophoresis
PCR guide & troubleshooting

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