Bio-Rad CHEF-DR II System - Manual (Page 4)

Section 1
General Information
1.1 Safety
The CHEF-DR II system uses high voltage and current and should be operated with care
at all times. The safety interlocks are for your protection and should not be circumvented. To
avoid shock, set up the CHEF-DR II components in a dry area. Immediately wipe up any
spilled buffers or salt solutions.
When pausing or aborting a run, always check that the current display goes to zero or
displays OFF. This can take 2-5 seconds while the power supply discharges. It is then safe to
remove the lid from the chamber.
Warning: There are high voltages and currents within the chamber, which can be harm-
ful. Do not attempt to circumvent these safety interlocks. Always turn off the power to the
chamber before working within the electrophoresis cell.
The Model 1000 Mini Chiller is ground isolated. Although there is virtually no current
flowing through the Tygon ® tubing into the chiller, you should avoid assembling or disas-
sembling the tubing while the CHEF-DR II system is operating during a run.
When inserting or removing the external temperature probe, be sure that the control mod-
ule is turned off. Do not handle the probe with wet hands.
Definition of Symbols
Caution, risk of electric shock
Caution (refer to accompanying documents)
1.2 Overview
Pulsed field electrophoresis is a technique for resolving chromosome-sized DNA
molecules. By alternating the electric field between spatially distinct pairs of electrodes,
megabase (mb) sized molecules are able to reorient and move at different speeds through the
pores in an agarose gel. Overview articles and specific applications are listed in the refer-
ences in Section 8.
The CHEF-DR II system is based on CHEF 31,215 (Clamped Homogeneous Electric Fields)
technology. CHEF exhibits two unique properties which have made it the most commonly
used PFGE technique. First, CHEF provides highly uniform, or homogeneous, electric fields
within the gel. This is accomplished using an array of 24 electrodes, which are “clamped” or
held to intermediate potentials to eliminate lane distortion. Thus, lanes are straight. Second,
CHEF generates a 120° reorientation (field) angle, due the hexagonal geometry of the elec-
trode array, which is the optimal angle for separating DNA molecules ranging from 100 kb
to 6 mb in size. In addition, the CHEF-DR II system maintains homogeneous electric fields
using patented Dynamic Regulation
216 (DR). With DR, the electrodes not only generate the
electric field, but also sense changes in local buffer conductivity due to buffer breakdown,
change in buffer type, gel thickness, or temperature. Voltage potentials are readjusted imme-
diately to maintain uniform fields, thus insuring high resolution separations during runs and
between runs. These properties make the CHEF-DR II system a cost-effective instrument for
separating everything from Yeast Artificial Chromosomes (YACs) to cosmid inserts.
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