Sometimes when I run my Glycine SDS-PAGE, the separation of proteins (and ladder, also!) stops by the middle of the gel. This is getting more recurrent, since my last 2 gels have had this problem. The tracking dye reaches the bottom of the gel, but the samples separate only until middle. Although it seems weird, the ladder is well separated, but it seems like the power was turned off by the middle of the run.
Do you have some opinion on what is happening? What can I do to solve the problem?
I assume that you are not running a gradient gel or one designed to determine iso-electric points and that the gel running buffer is compatible with the gel (if it is pre-cast)
One possible answer is that your powerpack is set to run to a fixed voltage or current and there is a current / voltage overload safety cut-out when a safe limit is reached. This ensures that your gel does not overheat. .
You could get round this problem by lowering/changing your existing gel running conditions.
Also check that you do not have a slow leak in your gel tanks and the buffer in the top chamber has not fallen below the level of the gel. Also check that you have not got an accumulation of bubbles at the bottom of your gel -i.e electrical conductivity is not broken
Ian
Perhaps a timer had been set in your AC/DC converter? I agree with Ian that you try to lower your running voltage and make sure everything (short and long plates and frames) is tight in contact before you run your next SDS-PAGE.
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