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.
Posted 23 May 2010 - 06:11 AM
Posted 23 May 2010 - 07:00 AM
Posted 23 May 2010 - 08:49 AM
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.