Bio-Rad PROTEAN® i12™ IEF System - Manual (Page 16)

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Chapter 2 Basic Operation
PROTEAN i12 IEF System Instruction Manual
Sample cup
Cup Loading (IEF with Gel-Side Up)
Sample cups (catalog #164-6020) offer an alternative method of sample loading. Their use can improve
resolution, especially at extreme pH ranges (see Appendix B, Sample Loading Methods and Running
Configurations, for guidelines on when to use cup loading). The PROTEAN i12 sample cup assembly
consists of a sample cup holder that holds 1–12 disposable sample cups.
1. Using forceps, place the rehydrated IPG strips gel-side up in the channels of the focusing tray (Figure 2.3,
A). Position the positive (+) end of the IPG strips against the positioning stops in each channel.
2. (Recommended) Wet the gel-side up electrode wicks (notched) with deionized water and blot off excess
water. Use two wicks per IPG strip: place a wick at each end of each IPG strip (Figure 2.3, B).
3. Position the electrode assemblies in the focusing tray and press down on the green tabs to snap the
electrode assemblies into place (Figure 2.3, C). Place the focusing tray on the Peltier platform and
connect the electrodes to the instrument (see Section 2.1.2, Connecting the Electrodes).
4. Prepare the sample cup assembly by placing the sample cups into the slots of the sample cup holder
corresponding to the channel with the rehydrated IPG strip (Figure 2.5).
5. Clamp the sample cup assembly onto the edges of the focusing tray, on top of the IPG strips and next to
either electrode (Figure 2.5). (Placement depends on the pH gradient and the sample. See Appendix B,
Sample Loading Methods and Running Configurations.)
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Two flexible arms on
the sample cup holder
apply gentle pressure
onto the sample cup to
ensure a complete seal
between the IPG strip
and the sample cup.
Once the sample cup
holder is positioned,
any horizontal
movement will damage
the IPG strips.
Fig. 2.5. Placement of the sample cup assembly onto the focusing tray.
Insert sample cup at an angle
6. Load 25–250 µl sample
into the sample cups (larger
volumes of dilute samples
may be loaded, up to 400 µl).
Overlay both the sample in
the sample cup and the IPG
strip with mineral oil.
7. Select or program the
protocol(s) and start the run
(see Section 2.3, Starting the
Run).
Sample cup holder