Figure 1. Microloader device preparation.

Fine tip transfer pipettes (#233, #235, Samco Scientific) were used for the assembly of sample microloaders. Pipette tips were cut to obtain an outlet passage length of 1 cm and a reservoir length less than 1 cm and a 4% polyacrylamide stacking gel was introduced through the outlet passage by capillary action. After stacking gel polymerization, sample microloaders were firmly inserted into a 1 mm-thick acrylamide gel and the reservoir was loaded with running buffer. Special care was taken to avoid bubbles and to ensure close contact between microloaders and gel. A total of 1-15 μl of sample was loaded into each microloader, and electrophoresis was performed at a maximum of 100 V until samples entered into the gel, after which voltage could be increased up to 200 V.