Bio-Rad CHEF-DR II System User Manual
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Figure 1.1 A shows the relative potentials of each electrode pair when the + 60° vector
(indicated by the arrow) is activated. Net field vector is from NW to SE. The highest poten-
tials are found along the SE segment of the hexagon. The potentials gradually decline along
the adjacent segments. The NW segment, directly opposite the SE, has 0 potential, repre-
sented in the diagram as negative terminals. When the - 60° angle is activated, the pattern of
electric charges is as shown in Figure 1.1 B. Together, the two pulses result in a 120° includ-
ed field angle. Other angles will result in values for the relative electrode potentials, accord-
ing to predetermined values.
Fig. 1.1.
Voltage Clamping by the CHEF-DR II system.
A.
Relative electrode potentials when the + 60°
field vector is activated.
B.
Relative electrode potentials when the - 60° field vector is activated.
Electrophoresis Cell
The CHEF-DR II electrophoresis cell consists of a 43 x 44 cm (17” x 17.5”) acrylic box
with 24 horizontal electrodes arranged in a hexagon. Gels are electrophoresed horizontally,
submerged under recirculated buffer. A 14 x 13 cm (5.5” x 5”) gel is cast on a platform in a
separate casting stand. The platform (along with the gel) is removed from the casting stand,
and placed in the center of the hexagon. The platform is held in place by a frame positioned
on the chamber floor. A combination wide/long format is available as an accessory (catalog
number 170-3704). DNA migration and buffer flow is in the direction of the arrow mounted
on the lid.
The electrodes are individually wired to the 24 pin computer cable, which in turn connects
to the drive module. The individual electrodes are replaceable for easy maintenance (see
Section 6). Electrodes are 0.01” diameter platinum wire. They are each sealed with an O-ring
and silicone sealant to provide double protection against leakage. The electrodes will wear out
more rapidly when switch times below 1 second are used, and/or when 6 V/cm gradients are
employed.
There are two small chambers below the level of the main chamber floor at the front and
rear of the main chamber. These chambers are used for buffer circulation and priming the
pump. Buffer enters the main chamber through 6 holes in the floor near the top. A flow baf-
fle is located just in front of these holes to prevent gel movement. Buffer exits the chamber
at the front through the T fitting. One arm is for draining, the other for circulation. The base
of the chamber has four leveling screws for even gel submersion in buffer.
The lid contains an interlock for safety. The voltage directly passes from the drive mod-
ule through a short-path in the lid interlock. If the lid is removed, the current flow is broken
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