Bio-Rad CHEF-DR® III Variable Angle System - Manual (Page 4)

Section 1
General Information
1.1 Safety
The CHEF-DR III 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 circumvent-
ed. To avoid shock, set up the CHEF-DR III 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
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 the safety interlocks. Always turn off the power to the
chamber before working within the gel box.
The Cooling Module is ground isolated. Although there is virtually no current flowing
through the Tygon ® tubing into the chiller, avoid assembling or disassembling the tubing
while the CHEF-DR III system is operating.
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 DNAs. By
alternating the electric field between spatially distinct pairs of electrodes, megabase (mb)
sized DNAs are able to reorient and move at different speeds through the pores in an agarose
gel. Overview and applications articles are listed Section 8.
The CHEF-DR III system separates large and small DNA fragments with better resolu-
tion, speed, and accuracy, than initial pulsed field methods. DNAs from 100 bases to over 10
megabases (mb) may be effectively resolved. For example, the chromosomal DNA of
Schizosaccharomyces pombe can be resolved in 1 day using a 106° pulse angle, compared to
2 days at 120°. Everything from Yeast Artificial Chromosomes (YACs) to M13 inserts can
be separated with a single instrument. Applications include top down and bottom up map-
ping (Not I and cosmid cloning, respectively), electrophoretic karyotyping, analysis of tumor
cell DNA rearrangements, mammalian DNA analysis, and testing for bacterial, yeast, and
parasite strain homogeneity.
The CHEF-DR III system uses two leading technologies, CHEF (Clamped Homogeneous
Electric Fields) 215 and PACE (Programmable Autonomously Controlled Electrodes). 216 The
system provides highly uniform, or homogeneous, electric fields within the gel, using an array
of 24 electrodes, which are “clamped” or held to intermediate potentials to eliminate lane dis-
tortion. Thus, lanes are straight. The system maintains uniform fields using patented Dynamic
Regulation (US Patent 4,878,008). The electrodes sense changes in local buffer conductivi-
ty due to buffer breakdown, change in buffer type, gel thickness, or temperature, and poten-
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