Bio-Rad Rotofor® and Mini Rotofor Cells - Manual (Page 15)

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3.7 Remove Air Bubbles
During filling, air bubbles can become trapped in the 6 ports of the electrolyte chamber.
This is especially true with the mini focusing chamber. If the bubbles are not removed, they
will produce occasional fluctuations in the voltage and currents due to the discontinuity they
create in the electrical field. Some power supplies, such as the Bio-Rad Power Pac 3000,
have safety sensors that may trip and shut off the voltage in response to the resistance
change that occurs when a bubble rotates into the electrical circuit. Thus, bubbles must be
eliminated prior to commencing electrophoresis. Remove the assembled, loaded cell from
the stand, turn it vertically and tap the electrode chamber to dislodge the bubbles. Then
turn the cell 180° and tap the other chamber. If any air bubbles remain in the 6 ports
between the sample and the ion exchange membranes, repeat this process. When all the
bubbles are eliminated from the electrode ports, return the cell to the stand and start the
fractionation.
Fig. 3.6. Loading the sample.
Section 4
Running Conditions
4.1 Starting the Fractionation
Excessive heating may denature proteins and damage the Rotofor cell.
Connect the ports of the cooling finger to a source of recirculating coolant and
begin coolant flow. The ports are interchangeable, so either one may be connected
to the coolant inlet. It is usually sufficient to set the chiller at 4°C. For more critical
temperature control, the chiller can be adjusted accordingly. At 12 W constant
power (normal operating mode) the coolant temperature should be set at 10°C less
than the temperature desired for the sample. In other words, if the coolant is -6°C
than the sample temperature will be maintained at about 4°C. Attach the cover of
the unit, mating its jacks to the plugs on the base. Allow the system to come to
thermal equilibrium at the cooling temperature before beginning the run, approximately
10–15 minutes.