Ways To Ensure Experimental Consistency #2

The following is pretty obvious but does deserve a mention because sometimes, the obvious get overlooked.

Aliquoting

Some things don’t handle temperature changes too well and there are going to be times when enzymes, antibodies, etc get forgotten and left out on the bench for way longer than it should. As such, it is good practice to make aliquots because if something goes wrong, you will have backups! For instance, if you want to preserve your PCR enzyme and keep it at maximal efficiency for the life of the kit (i.e. however long it takes you to use it up), make aliquots of the polymerase. That way, the enzyme will undergo less freeze-thaw cycles and if you happen to forget about it and leave it out on the bench overnight, you can just grab a new aliquot. The same applies for antibodies. 

Mixing

Reagents, samples and solutions, etc sit around frozen, chilled or at room temperature waiting for us to use them. While they sit and wait, some chemicals will separate or you might get precipitates (think SDS falling out of solution when it gets cold). If you have solutions in large 1L clear bottles, it would be pretty easy to see, but if you had frosted 1.5-2ml microfuge/screw cap tubes or those brown opaque ones, it’s not going to be obvious (if at all). For instance, if you defrost your dNTP mix for PCR without giving it a good mix before taking a few mircoliters for your mastermix, would you expect to have a equivalent concentrations of all 4 dNTPs? So unless there is good reason not to mix something, its good practice to give small tubes a quick vortex and pulse spin to mix up the contents.

Other Things To Consider

* Use filter pipette tips. These come sterilized and DNase/RNase-free. The filter also prevents liquids and vapors from volatile solutions from going into the pipette barrel.

* Calibrate your pipettes regularly.

* Clean out the pipette barrel. It is amazing how much build-up you can get in the pipette barrel. You probably don’t need to do this as often if you are using filter pipette tips, but if you are not using filter tips, clean it regularly.

* If you make your own solutions, make sure that the date the solution is made, storage temperature and maker are clearly labeled.

* Some antibodies are very temperamental. If you get a batch that works, make sure to order a few more from the same batch.