Drying polyacrylamide without cracking - (Oct/20/2008 )
I have been trying to dry my 4-12% gradient polyacrylamide gel without success. I have tried soaking for 20 minutes in just deionized h20, various concentrations of methanol and glycerol, different gel dryers. We are using a vacuum gel drying system and we are able to get a gel to dry without cracking but only if the gel is an 8% gel. However, I need a 4-12% gradient. In all attempts I use two pieces of 3mm whatman paper, gel, and covered in saran wrap before placing on the gel dryer. As I said previously we have used various concentrations of ethanol/methanol and glycerol. Any help would be appreciated.
Are there any air bubbles between the Whatman paper and the gel, and between the wrap and the gel?
Try soaking the gel in 3% glycerol, and air drying it overnight in a frame rack with both sides exposed.
Yes, I agreed with Minnie Mouse. You have to make sure that there is no bubble between your gel and the filter paper.
From my experience, I just soaked my gel in dH2O for about a week, of course, I did change the dH2O several times over the week. Without soaking in glycerol, I hardly had any cracked gel. I did get a few cracked gels from time to time, but they didn't crack like a map, probably just a minor single crack.
How long are you drying? For a higher percentage gel you should dry up to 1.5- 2 hrs with an additional cool down period.
My gels were 12% gels. I dried them for 1.5 hours, if I dried multiple gels. If it was single gel, I dried for 1 hours. Normally, I just left them on the drier until I finished my works at the end of the day. Or the next person would take it out for me. Therefore, I didn't know the exact cooling time.
is the gel for radioactive samples?
for our protein gradient gels (5-15%) we equilibrate the gel with 5% glycerol in destaining solution (30% methanol, 5% acetic acid). this solution will prevent the gel from swelling.
then we would dry on a vacuum gel dryer, covering the gel with a porous polyethylene plate (bio-rad).
we would maintain heat and vacuum until the surface was equally hot (no cool spot where the gel is).
with a radioactive gel we covered with plastic wrap then put the porous plate over (it still seemed to help).
ensure that your gel doesn't swell prior to drying and you will significantly reduce the chance that it will crack.
also, don't release the vacuum until you are sure that the gel is dry or it will shatter.
all-in-all, you may want to take homebrew's advice and use a frame dryer.
Thanks all for the info. I have been very careful about no bubbles. I don't think the problem is occurring when the vacuum is released as I see the cracking before the release. I have been drying for 2 hr at 80 degrees. I guess our next step is a passive evaporation with a frame dryer. Will keep you posted.
I dried the gel for 2 hr at 60degree.
I really, really like these. you don't have to use the dryer, which I always thought lent itself to cracking. they're relatively cheap and easy as pie