| ExcelGel preparation
Two sizes of precast ExcelGel gradient SDS gels are available: The 110 x 250 mm gel contains an 8 to 18% acrylamide gradient, and the 180 x 250 mm gel contains a 12 to 14% acrylamide gradient. Either gel accepts a single 18- or 13 cm IPG strip, two 11 cm, or three 7 cm IPG strips. Placing shorter IPG strips end-to-end is ideal for comparative studies. For maximum resolution, the larger gel coupled with the 18 cm IPG strip is the best choice.
| Important: | A flatbed second-dimension system is not recommended if the first dimension has been run on a pH 6–11 IPG strip. |
A: Equilibrate the IPG strips.
Just prior to preparing the ExcelGel SDS gel, equilibrate the IPG strips .
B: Prepare the Multiphor II unit.
Set the temperature on the MultiTemp™ III Thermostatic Circulator to 15 °C. Pipette 2.5 to 3.0 ml of IPG Cover Fluid or kerosene onto the Multiphor II cooling plate.
C: Place the ExcelGel SDS gel.
Remove the gel from the foil package by cutting away the edges of the package. A notch at the lower-left corner of the film identifies the 18% or 14% (i.e., anodic) end.
| Note: | The gel is cast on a plastic support film and does not cover the film entirely. |
Markings on the plastic cover of the gel indicate the direction of electrophoresis. Orient the gel according to these markings, remove the cover, and place the gel on the cooling plate.
Note: Avoid trapping bubbles between the gel and the cooling plate. Avoid getting IPG Cover Fluid or kerosene on the gel surface, as this may cause the buffer strips to slide during electrophoresis.
Separation quality is improved if the gel surface is allowed to dry, uncovered, for about 5 minutes before proceeding.
D: Position the cathodic buffer strip (Figure 22).
| Peel back the foil on the colorless cathodic (–) ExcelGel SDS buffer strip. Place the buffer strip with the smooth, narrow face downward along and in complete contact with the cathodic (–) edge of the SDS gel. Avoid trapping air bubbles between the gel and the buffer strip. If the buffer strip breaks, piece it together on the gel. |  |
figure 22 |
| Note: | Vinyl gloves tend to stick less to the buffer strips than other types of plastic gloves. If sticking persists, dampen the gloves with distilled water or a 5% SDS solution. |
E: Position the anodic buffer strip.
Repeat step 4 with the yellow-colored anodic (+) Excel-Gel buffer strip, placing it along and in contact with the anodic edge of the SDS gel. | 
