Once you have set up your gel, pour in just enough sodium bicarbonate buffer to cover the solidified gel. Make sure you fill up the spaces left from where you cut away the gel—the gel and stainless steel wires should be completely submerged.
Gently remove the comb by pulling straight up without tearing the gel. The wells left by the comb should fill with buffer.
Use the needle-tip pipette to transfer approximately 10 microliters (µL) of each sample to an empty well. (The volume of the thin tip of the pipette is about 10 µL.) Submerge the tip in the buffer directly above the well and gently squeeze the sample into the well. It should fall into the well since it is denser than the surrounding buffer. Be sure to use a new pipette for each sample to prevent contamination between samples. If you have a limited supply of pipettes, thoroughly rinse out the tip in a large beaker of water before reusing.
Once all the samples are loaded, connect the leads from the power supply to the stainless-steel wire electrodes attached to the box. Connect the negative terminal to the electrode at the top of the gel (near the wells) and the positive terminal to the electrode at the bottom of the gel. You should see bubbles forming along the electrodes when a complete circuit is made.
Leave the power connected for 15–20 minutes and observe what happens to each sample.