To thaw or not to thaw
Posted 22 May 2010 - 10:18 AM
Posted 22 May 2010 - 10:41 AM
You need to mix the solution before using it, when thawing a part of it you will not have a good mixture.
Some substances will settle down so if you only take the top layer, you dont have everything.
I am not sure if this is the case of every buffer or solution you use, but just to be sure, I would thaw it completely.
If you don't know it, then ask it! Better to ask and look foolish to some than not ask and stay stupid.
Posted 23 May 2010 - 06:11 AM
When working with frozen buffers, is it required that you thaw the buffer completely before taking what you need or just letting it thaw enough to get what you need? Would the concentration of the components of the buffer be altered if part of it is still frozen? If so, is this the case for samples of nucleic acid or protein as well?
Posted 23 May 2010 - 07:00 AM
Posted 23 May 2010 - 08:49 AM
If you prefer not to thaw larger volumes than you need, you should consider making aliquots of certain volumes and freezing them individually. Then you can just take a smaller volume out of the freezer and thaw that.
I second this.
You must thaw your buffer completely followed by a good mix. Water tends to freeze first. And will do so from the surface of the bottle/tube inwards, creating a concentration gradient as various impurities (buffer components) are concentrated into the center of the container.
And yes you certainly do see this effect in DNA and protein. You can even test it by thawing a solution of DNA and sampling it with at various positions. Using a nanodrop spectrophotometer, you will find the DNA concentration varies fantastically, as much as a 5 fold difference.
If you are concern about repeated freeze thaw cycles, aliquot your sample into several smaller volumes.