Aliquots are like snack-size portions – they’re smaller portions of something you have a lot of. This could be something you make or something you order. We aliquot out aliquots all the time in the lab (yes, aliquot is also a verb). We do so so frequently because aliquots are super fab!! Why?

https://www.youtube.com/watch?v=Fg-_AOMMz3g&ab_channel=thebumblingbiochemist

Just like your chips get a little staler each time you open the bag, your samples get a little (or a lot) damaged each time you freeze-thaw them (water expands when it freezes, which can “break” molecules and/or mess up local concentrations of salts, etc. as the water pushes them out of its way). Making aliquots of stuff you have to freeze reduces the number of times what you use goes through that process. This is especially important for things like enzymes and other proteins as well as cells. 

Even if it’s not something that’s frozen, when you open the tube you expose stuff to air – which can lead to oxidation of things that are sensitive to oxygen (like DTT) and evaporation (which can mess up concentration) – and light (which can damage light-sensitive things like fluorescent dyes). Sometimes it doesn’t make sense to make single-use-size aliquots (such as for things you frequently use different amounts of, such as gel sample buffers) but even bigger portions are better from that huge ole stock container so you still reduce the number of times you expose the stuff to the environment. 

It’s not just air and light that you’re exposing that stuff to when you go to use your sample… So let’s talk about double-dipping! When you stick that pipet tip in, even if you just open the tube to whatever dust, etc. is floating around, you’re contaminating your sample. This can be a big issue for solutions you’re trying to keep nuclease-free for work with RNA or DNA you don’t want to degrade. “Double-dipping” (taking stuff out of a tube, etc., multiple times) can also be an issue at any time if you accidentally have something on your tip that doesn’t belong there or you accidentally pipet something into that solution instead of wherever you meant to pipet into. 

In any of those cases, you don’t want that contamination to be of your stock solution! I mean, you don’t want it to be in your aliquots either, but better one of the aliquots than the stock! If there’s a problem with an aliquot, you can just get another one rather than have to remake the whole stock!

You don’t have to aliquot it all at once. Especially if that would mean filling up a bazillion boxes in your already-crowded freezer. Instead, you can aliquot out some into small portions and some in medium portions and then use up those small ones then make more small ones from the medium ones. 

Remember to put the date on the aliquots (either on the tubes themselves (best) or on the box they’re in). That way, if you suspect an issue when you use an aliquot you know which batch it came from and can check it. If you have a lot of aliquots it can be helpful to make some sort of shorthand mark like a colored line on the tubes and then put the details on the box. Printable labels can be great, too, but be careful that they don’t fall off!! This can especially be an issue for things you flash freeze & put in the -80. I like to put some sort of mark on the tube with permanent marker to identify it even when using one of those labels. I’ve heard that some labs have machines that print labels directly on the tubes which sounds so freakin’ awesome!

Aliquots can also be time-savers; for frozen stuff, they shorten the amount of time you have to wait for stuff to thaw since smaller portions thaw faster. You also can save time if you pre-measure them when aliquoting so you don’t have to measure when you go to use them. And you can save yourself time when aliquoting by using a repeater pipet or a multichannel pipet. More about those here: https://youtu.be/arRFvdx_cRc & https://youtu.be/Kzob9UFkwH8 

When you make aliquots, be sure to spin the tubes down before storing them (especially before freezing) to draw down liquid into the bottom of the tube and prevent sample loss due to evaporation and tube-wall-sticking: https://youtu.be/5VjTpA3ns3g 

“Aliquot” should really be a more common word in the world outside of the lab so feel free to popularize it at your next party! Aliquot of chips anyone?

Link to YouTube of today’s video: https://youtu.be/Fg-_AOMMz3g

Leave a Reply

Your email address will not be published. Required fields are marked *