Sending Plasmids: How to Avoid Jail Time and Shredded Envelopes

Whether you need to get your plasmid DNA to a lab on the other side of the world, or a few hundred miles down the road, it’s important to make sure your precious sample gets there, it is not degraded, and you don’t end up in jail. Here’s the Bitesize guide on how to send plasmids in the mail.

In solution

Plasmids are fairly stable in TE at room temperature. The EDTA in TE chelates magnesium in the solution, ensuring that any DNAses, which require Mg for activity, remain inactive. So, it is fine to send a plasmid dissolved in TE, in a tightly-capped tube. However, as Mortimer and Kahn, in their short 2001 Biotechniques note (free registration required) point out – if the tube is mailed in a standard envelope, the tube can get jammed up and shredded in the post office’s automatic sorting machines, which don’t accept envelopes wider than 2mm.

They suggest either using padded envelopes, which are not put through automatic sorting machines or pipetting the DNA into a thin-walled polyethylene tube and sealing the ends with a flame (see their paper for more details). Using a thin tube will stop the envelope getting stuck in the post office’s machines.

On filter paper

Another way to get your plasmid through the automatic sorting machines is to spot it onto a very small disc of filter paper. Cut out the filter paper, spot 10 microlitres of plasmid solution onto it, allow it to dry for a few minutes, then cover with sandwich wrap.

All the recipient has to do is pop the disc into a microfuge tube containing some clean TE and at least enough DNA for a transformation will re-dissolve into the TE. Make sure the filter paper disc is small enough to allow it to be submerged in 10-50 microlitres in a microfuge tube. The recipient won’t thank you for the task of cramming an A4 piece of filter paper into a small tube.

Remove the water

The ultimate way to send plasmid DNA is in dried form. It’s a bit more time consuming, but plasmids are much more stable in dried form because the things that degrade DNA – DNases and hydrolyses – require water. So with dried DNA there is no problem if you are shipping your plasmid halfway round the world, it gets stuck in a hot customs room for 2 weeks, then sits on the recipient’s bench for a month.

The simplest way to dry a DNA sample is to precipitate it (e.g. by ethanol precipitation), but omit the final resuspension step. A more thorough – although more expensive – method of drying DNA is lyophilization, using a speedvac for example.

In your pocket? – Not advisable

One final point to note is that if you need to get your plasmid into another country, then mailing is the best option. Don’t be tempted to take it yourself. I know people who have carried plasmid DNA in their through customs, but that’s probably a bad idea. If caught, the responsibility lies with you as an individual and, as an example, US Customs levies penalties of up to 250,000 USD, and/or a jail sentence for non-compliance.

How do you send your plasmids to other labs?

Dr Nick Oswald

Nick has a PhD from the University Dundee and is the Founder and Director of Bitesize Bio, Science Squared Ltd and The Life Science Marketing Society.

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