GE SE 250 Mighty Small II Operating Instructions Manual page 45

Error description
Protein streaks verti-
cally
Unusually slow (or
fast) run
Bands are skewed
or distorted
Stained sample col-
lects
SE 250/260 Mighty Small II Operating Instructions 29281629 AA
Corrective action
Centrifuge or filter sample before loading to remove particu-
lates.
Dialyze or desalt the sample.
To increase or decrease the migration rate, adjust the voltage
or current by 25% to 50%.
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 a fresh buffer.
Dispose of older acrylamide solutions and use only stock
•
of the highest quality.
Only use freshly deionized urea.
•
Check gel preparation and polymerization.
De-gas the stacking gel solution and avoid trapping air bub-
bles 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 particu-
lates.
Near the buffer front:
Protein is not sufficiently restricted by the resolving gel;
•
increase the % T.
Near the top of the gel when the buffer front has reached the
bottom:
The gel pore size is too small. Decrease the % T of the re-
•
solving gel.
The protein has precipitated. Heat the sample at a lower
•
temperature (70°C or less) for 1–2 minutes.
7 Troubleshooting
45