Storage of BSA Standards - (Jan/09/2012 )

Hey!

I currently make my BSA standards (1/.8/.6/.4/.2mg.ml) in PBS and store them in the -80 freezer and use them to make a new curve every time I prepare proteins. I have been hearing that some people make them fresh every time and others seem to store the dilutions in the fridge.

Just wondering if there is any difference to the storage methods, are any better than the other?

Also, is there a standard length of time people keep the dilutions before making fresh standards?

Thanks for any advice! :-)

BSA standards for protein quantitation (e.g. by BCA or bradford)?

If so, storage frozen is definitely better than in the fridge, where they would be more prone to bacterial or fungal growth. As most quantitation methods rely on oxidation of specific residues on the proteins of interest, I think that freezing them and thawing a maximum of 2-3 times should be OK.

We used to make fresh, and used them within one day. I was taught to make a new std curve with each run, but that was also in a stricter lab.

We store our BSA as a concentrated stock (2g/L) in aliquots in the freezer (-20^oC) and make (dilute) the standards fresh every time we need to run a curve.

We are usually storing the BSA standards for BCAkit in the fridge, but not for longer than 3 to 4 weeks. We never had any problems with bacterial growth or anything. I think that 4°C storage for proteins which are used quite frequently is better thank repeated freezing and thawing.
The sealed stock solutions are stored at RT, as they are also shipped that way.

PippiLa on Tue Jan 10 14:21:49 2012 said:

Proteins degrade quite fast at fridge temperature, especially if there is any sort of protease contamination, which there shouldn't be in BSA.
The sealed stocks are prepared under very specific conditions, which include being in a non-oxidising atmosphere (usually N2), so that there is no chance of them degrading through oxidation. Once the vials are open, they should be stored as you would for any other protein solution.

Thanks everyone!

You can buy stabilized ampoules of BSA. One ampoule yields about 3 replicates of a standard curve. This is how the BCA kit sold by Pierce/Thermo comes.

Obviously you'd be remaking your curve with each plate this way.