The
rehydrated strips were positioned in the focusing tray and covered
with 2 ml of mineral oil (Bio-Rad) to prevent evaporation. Isoelectric
focusing (IFE) was conducted by stepwise increase of the voltage as
follows: 250 V, 20 min, 4000 V, 120 min (linear) and 4000 V (rapid)
until the total volt-hours reached 14 kVh.