Hoefer TE 22, User Manual, Page: 25 / 34

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Instrument guidelines
Cooling
Considerable Joule heat is generated during any
transfer because of the high current employed,
so active cooling is recommended, especially for
transfers requiring more than one hour, protein
transfers where biological activity must be
retained, or transfer of nucleic acids. (The high
conductivity of the phosphate buffer used by
Bittner
et al. (1980) leads to a relatively rapid
temperature rise.) Buffer temperature should not
exceed 45 °C because the cassettes and electrode
supports may warp. Use a circulator bath set to
10 °C if using water as a coolant. (You can use
a lower setting if the coolant is 50/50 ethylene
glycol/water.) Never leave the unit unattended
for more than one hour under high power condi-
tions (>250 mA).
Power setting
If using a power supply that can be set to either
constant current or constant voltage mode, we
recommend that it be set to operate in constant
current mode. Buffer conductivity increases with
temperature. During blotting in an uncooled
chamber, Joule heating and rising conductivity
may result in dangerous overheating if the power
supply is set to maintain constant voltage. If a
constant voltage power supply must be used,
monitor and adjust the voltage to maintain a
current at or below 400 mA.