Hoefer SE640 - Manual (Page 29)

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Time
A run is complete when the tracking dye reaches
the bottom of the gel. A 1.5-mm thick Laemmli
SDS gel, run at 25 mA/gel without cooling, usu-
ally requires 2.5 hours.
Electrophoresis parameters for
DNA/acrylamide gels
DNA gels are usually run at a constant voltage
setting, and since buffer systems are continuous,
both current and voltage readings remain con-
stant throughout the run. Running conditions
are expressed in units of V/cm. Published run-
ning conditions vary widely, but voltages in the
range of 1 to 3 V/cm are common for overnight
runs.
Record each run
Keep a record of the current or voltage setting,
number and thickness of gels, buffer system, and
the starting and final current or voltage readings
for each run so that results can be compared.
Inconsistent results for the same system and set-
tings indicate potential problems such as leaking
current, incorrect buffer concentrations, high salt
concentrations or inconsistent chemical quality.
Check band progress after 5 minutes, and again
after an hour, keeping an eye on the migration
rate of the tracking dye. The run is complete
when the tracking dye reaches the bottom of
the gel. Watch the buffer level and, if necessary,
replenish it as required to keep the top electrode
submerged. (A small volume of buffer may leak
past a nicked plate or gasket, or buffer may pass
through the gel.)
Caution! After initial monitoring,
do not leave the unit unattended
for more than 1 hour before
checking the progress of the
bands and the buffer level.