📦PLASMID STORAGE

This page describes two validated methods for plasmid preservation and shipment without the need for cold chain transport: drying on filter paper and ethanol precipitation.

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Plasmid Storage by Filter Paper and Ethanol Precipitation

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📄 Method 1: Storage Plasmids on Filter Paper

🧪 Materials

• Clean Whatman No. 1 filter paper (or equivalent)

• Sterile scissors or punch

• DNA plasmid solution (≥0.3 μg)

• Sealed plastic bag (e.g., Ziploc)

• Heat sealer (optional)

• Sterile microcentrifuge tubes

📌 Drying and Packaging

1. Using a clean Whatman No.1 filter paper (or equivalent), mark a circle with a pencil. Avoid using ink or markers.

2. Spot approximately 0.3 µg of plasmid DNA (ideally in 1 µL with 0.3 µg of plasmid) into the marked circle.

3. Let the spot air-dry at room temperature in a sterile environment.

4. Place the dried paper in a plastic bag and seal it (preferably heat-sealed).

5. Send the sealed paper via standard mail or courier.

📌 Recovery

1. Using clean gloves and sterile scissors, cut out the marked circle.

2. Place the paper in a 1.5 mL microcentrifuge tube.

3. Add 50 μL of Nuclease-free ddH₂O, vortex briefly, and incubate for 5 minutes at room temperature.

4. Vortex again and spin down briefly.

5. Use 2-5  μL of the supernatant for bacterial transformation by electroporation or chemical methods.

Note: A pipette tip can also be used to gently grind the filter paper inside the tube to improve plasmid release before vortexing.

1. This DNA is suitable only for transformation and plasmid propagation, not for direct enzymatic reactions or sequencing.

2. Store the plasmid at −20°C or −80°C as a backup.

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🧪 Method 2: Plasmid DNA Precipitation with Ethanol

🧪 Materials

• Plasmid DNA (1 ng–2 μg)

• Sterile water (ddH₂O)

• 100% ethanol

• 3M sodium acetate (NaAc)

• 75% ethanol (cold)

• 1.7 mL microcentrifuge tubes

• Centrifuge (10,000 rpm)

• Heat block or speed-vac

📌 Precipitation and Shipping

1. Transfer plasmid DNA to a 0.5 or 1.5 mL Eppendorf tube.

   • If the volume is <50 μL, add ddH₂O to reach 50 μL

2. Add 2 volumes of 100% ethanol.

3. Add 0.1 volume of 3M sodium acetate.

4. Mix and incubate at −20°C for 30 minutes (overnight improves recovery).

5. Centrifuge at 10,000 rpm for 15 minutes.

6. Discard the supernatant.

7. Wash the pellet with 100 μL of cold 75% ethanol.

8. Centrifuge at 10,000 rpm for 10 minutes.

9. Remove all remaining ethanol.

10. Dry the pellet using a speed-vac, or leave it open at room temperature or at 37°C.

📌 Rehydration

• Before use, add 10 μL of ddH₂O to resuspend the DNA.

• Proceed with bacterial transformation

Note: This DNA is suitable only for transformation and plasmid propagation, not for direct enzymatic reactions or sequencing.