Bio-Rad Trans-Blot® Plus Cell - Manual (Page 18)

2. Current limits
The PowerPac 200 Power Supply is capable of a 200 Volt output. Unless a
current limit is set, uncontrolled conductivity changes may result in full power
being delivered to the Trans-Blot Plus cell. The transfer buffer may heat up
(further increasing conductivity), resulting in a potential safety hazard. Refer to
the PowerPac 200 Power Supply Instruction Manual for setting current limits
and run times.
3. Polarity of transfer
Do not reverse the polarity of the plate electrodes. This will result in corrosion
and rusting of the stainless steel cathode. If this should occur, the stainless
steel should be cleaned with a mild, non-abrasive cleanser to remove the rust.
4. Dissipating Heat
Electrophoretic transfer entails large power loads and consequently, heat
generation. The use of the Super cooling coil and a refrigerated circulating bath
is required for high intensity field transfers and is recommended for long,
unsupervised runs. Pre-chilling the buffer or the use of ice blocks are common
practices for heat dissipation in blotting, yet their application for the Trans-Blot
Plus cell should be limited to only runs lasting less than 1 hr and requiring less
than 150 Watts total power.
Placing the Trans-Blot Plus cell in the cold room is not an adequate means of
controlling transfer buffer temperature. The tank of the Trans-Blot Plus cell is
an effective thermal insulator, thus it limits the efficient dissipation of heat.
6. Using a stir bar during transfer
For all blotting applications, a stir bar must be placed inside the Trans-Blot Plus
cell, so that the transfer buffer is stirred during the course of the experiment.
This will help to maintain uniform conductivity and temperature during
electrophoretic transfer. Failure to properly control transfer buffer temperature
results in poor transfer of macromolecules and poses a potential safety hazard.
7. Transfer buffer pH
Do not adjust the pH of transfer buffers unless this is specifically indicated.
Adjusting the pH of transfer buffers, when not indicated, will result in increased
buffer conductivity, manifested by higher initial current output and decreased
resistance.
8. Transfer buffer recommendations
Use only high quality, analytical grade methanol. Contaminated methanol can
cause increased transfer buffer conductivity and poor transfer. Reusing the
transfer buffer is not advised, since the buffer will likely lose its ability to
maintain a stable pH during transfer. Diluting transfer buffers below their
recommended levels is also not advised, since this will decrease their buffering
capacity.
9. Voltage limits
Do not increase the voltage settings beyond those indicated in Tables 3.1–3.4
for overnight operation. Buffer conductivity must be close to the current listed
and a current limit should be set on the power supply. If overnight transfers at
low voltages are ineffective, and higher voltages are necessary, then decrease
the transfer time and use active cooling with the higher voltage settings. Failure
to decrease transfer time and use cooling may result in a safety hazard.
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