Bio-Rad Model 422 Electro-Eluter - Manual (Page 7)

Section 4
Model 422 Electro-Eluter Assembly
1. Soak the Membrane Caps at 60 °C in elution buffer (see Section 9 for buffer recipes) for
at least 1 hour prior to use. Membrane caps may be soaked for longer than 1 hour. Wear
gloves when handling the membrane caps to prevent the dialysis membrane from becom-
ing contaminated. Membrane caps may be reused. If they are to be reused they must be
stored in elution buffer containing 0.05% sodium azide (NaN
3
) in the refrigerator. They
do not need to be reheated or resoaked when reused.
2. Take the appropriate number of Glass Tubes and place one Frit in the bottom of each
tube. Set the tube on a clean paper towel and, if necessary, push on the Frit from inside
the Glass Tube to insure that the Frit is flush with the bottom of the glass tube. Next, push
the Glass Tube and Frit into the electro-eluter module. It is easiest to do this by wetting
the grommet with elution buffer and sliding the Glass Tube in place. Make sure the Glass
Tube is even with the top of the grommet and the Frit is flush with the bottom of the
Glass Tube. Fill any empty grommet holes with stoppers.
3. Wear gloves when handling the Membrane Caps to prevent contamination of the dialy-
sis membrane. Place one pre-wetted membrane cap in the bottom of each Silicone
Adaptor. Fill the adaptor with elution buffer. Pipet the buffer up and down to remove any
air bubbles around the dialysis membrane.
4. Slide the Silicone Adaptor with the membrane cap onto the bottom of the Glass Tube
with Frit. Some tiny air bubbles may come out of the Frit. Pull the Silicone Adaptor par-
tially on and off a few times to make sure all the air bubbles are expelled. All air bubbles
must be removed from the Frit for best elution yields. See Figure 1.
Note: The glass tubes for the Model 422 Electro-Eluter have one frosted end. The white
silicone adaptor must be placed on the frosted end, or it may slip off during electro-elution.
Fig. 1. Side view of Model 422 Electro-Eluter assembly. The vertical glass tube is filled with elution
buffer. The negative electrode is at the top. The positive electrode is below the membrane cap.
Macromolecules are carried by the electrical current out of the gel slice, through the Frit and into the
membrane cap. The molecules are retained by a dialysis membrane which is molded into the cap.
4
Glass tube
Silicone adaptor
Gel slice
Frit
Membrane cap