Bio-Rad CHEF Mapper® XA System - Manual (Page 8)

Fig. 1.1. Voltage clamping by the CHEF Mapper system. A. Relative electrode potentials when the
+ 60° field vector is activated. B. Relative electrode potentials when the - 60° field vector is activated.
Fig. 1.2. Voltage clamping by the CHEF Mapper system In the FIGE mode. A. Relative electrode
potentials when the 0° field vector is activated. B. Relative electrode potentials when the 180° field
vector is activated.
Electrophoresis Chamber
The CHEF Mapper electrophoresis chamber consists of a 44.2 x 50.3 cm (17.4” x 19.8”)
polycarbonate box with 24 horizontal electrodes arranged in a hexagon. (See Figure 1.3.)
Gels are electrophoresed horizontally, submerged under recirculated buffer. A 14 x 13 cm
(5.5” x 5.1”) gel is cast in a separate casting stand, removed, and placed in the center of the
hexagon. It is held in place by a frame, with pegs which are inserted into holes on the cham-
ber floor. A longer and wider format is available as an accessory. DNA migration and buffer
flow are in the direction of the arrow on the lid.
The heavy duty, 0.02” diameter platinum wire electrodes, replaceable for easy mainte-
nance (see Section 10), are individually connected to the 24 pin computer cable, which in
turn connects to the power module. 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 sec. are used and/or when 9 V/cm gradients are employed.
The two small chambers below the main chamber floor at the front and rear of the
main chamber are used for buffer circulation and priming the pump. Buffer enters the
main chamber through six holes in the floor near the rear. A flow baffle just in front of these
holes prevents gel movement. Buffer exits the chamber at the front through the left port.
The right front port is for draining. The base of the chamber has four leveling screws for
even gel submersion in buffer.
– – – –
+ + + +
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A. 0
°
B. 180
°
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– – – –
+
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➤
+ + + +
+ + + +
+
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A. + 60 ° B. - 60 °
➤
+
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+ + + +
+
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–
–
–
–
–
–
–
–
+
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➤
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