Hoefer SE250 - Manual (Page 23)

5. Troubleshooting
problem solution
Smile effect on the buffer front To reduce the running temperature:
• Circulate coolant through the upper buffer
chamber core.
• Prechill the buffer.
• Decrease the current or voltage setting. (10 mA per
0.75 mm gel, 15 mA per 1.5 mm thick gel.)
• Run the gel in the cold room.
Protein streaks vertically • Centrifuge or filter sample before loading to remove
particulates.
• Dialyze or desalt the sample.
Unusually slow (or fast) run Adjust the solutions:
• Check recipes, gel concentrations, solutions, and
dilutions. (For instance, do not use Tris-HCl instead
of Tris.)
• If the required pH of a solution is exceeded, do not
back-titrate. Prepare fresh buffer.
• Dispose of older acrylamide solutions and use only
stock of the highest quality.
• Only use freshly deionized urea.
Adjust the voltage or current settings:
• To increase or decrease the migration rate, adjust
the voltage or current by 25–50%.
Bands are skewed or distorted Check gel preparation and polymerization:
• Degas the stacking gel solution and avoid trapping
air bubbles under the comb teeth.
• Overlay the running gel with water-saturated
n-butanol before polymerization begins to avoid
forming an uneven gel surface.
Check sample preparation:
• Dialyze or desalt the sample.
• Centrifuge or filter sample before loading to remove
particulates.
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