Hoefer SE900 - Manual (Page 27)

• p21
Problem Solution
Gradient gels-uneven layering Add sucrose (15% final concentration) or glycerol (25% final concentration)
to the high-percent monomer solution.
Solutions pumped in too fast. Add a small amount of bromophenol blue
to the heavy solution to track the gradient formation. Allow for solutions to
underlay without excessive mixing.
Caution! Excessive amounts of bromophenol blue inhibit polymerization.
Electrophoresis Run Problems
Dye front curves up (smiles) at the edges
This indicates current leakage at the spacers. Make sure to clean the plates
well at the spacer edges, that the sides are free of dirt or grease, and that
the gel is fully polymerized before removing from the caster.
Gels have been run with hinge side toward the top of the tank. The hinge
also seals the lower edge of the gel from electrical leaks. It is best to place
cassettes hinge side down to get the straightest dye fronts.
Inadequate buffer at the top. Make sure the buffer is filled ½ way through
the top spacer to make the most even electrical field across the gel and
prevent the gel from drying out.
Too much buffer at the top of the gel. Make sure the buffer is filled ½ way
through the top spacer to make the most even electrical field across the gel
and prevent the current from bypassing over the gel at the top.
Check buffer recirculation is on and operating properly.
Use a refrigerated water bath to maintain even buffer temperature within
the tank.
Decrease the current or voltage setting.
Dye front curves down (frowns) at the edges Poor polymerization at the spacers. Make sure to clean the plates well at
the spacer edges, that the sides are free of dirt or grease, and that the gel is
fully polymerized before removing from the caster.
Power Supply detects current leak Cracked or broken alumina plate in the base of the separation tank. Contact
Hoefer or your distributor.
Poor draining of tank Drain fitting has become clogged with debris. Gently back-flush water
through the drain line.
Unusually long run times Too much buffer at the top of the gel. Make sure the buffer is filled ½ way
through the top spacer to make the most even electrical field across the gel
and prevent the current from bypassing over the gel at the top.
Poor reagent quality. Acrylamide solutions can build up acrylic acid over
time. Do not keep stock acrylamide solutions longer than ~3 months and
store acrylamide at 4 °C.
Buffer incorrectly prepared. Use the basic form of Tris. Do not adjust the pH
of the buffer after preparation.
Check power settings and adjust if necessary.