SDS-PAGE power supply issues - (Nov/04/2014 )

Hi,

So I have started to have problems with voltage and current when running my (mini) gels. Previously they have run fine when I set the voltage to 200V. The current stays around 20-30mA which is what it should be according to the manufacturer. However now when I try to run 2 gels nothing happens at all and I see no bubbles indicating there is no power. When I try 1 gel at 200V the current goes up to about 250 - 300mA and my samples do not run at all. The gel tank and power pack have been looked at and no issues have been found with these so I don't know what is going wrong?

The running buffer 10x stock I use is: Tris base (0.25M) 30.25g; glycine (1.92M) 143.25g; SDS (1%) 10g in 1000ml and I dilute this to 1x.

Please help!

when you say that the power pack has been "looked at" do you mean that its output was checked with a meter?

was the continuity of the electrodes and cables checked?

are the electrode wires clean?

when the current went up to 250-300, did you note where the system got hot?

did you note bubble formation at the electrodes during that run?

Also check that the buffer has been prepared properly (i.e. make some new), often this is the problem rather than the powerpack.

If it is a precast gel, make sure the sealing strip at the bottom is taken off.  Make sure the upper chamber electrolyte covers the wells and that the gel cassette is inserted in the correct orientation.