Native-PAGE of fractions of RBPs after preparative isoelectric focusing in a Rotofor cell in 1.1% ampholyte (pH 4.5-5.4). The end conditions after a 4 h fractionation were 1400 V and 8 mA at 12 W constant power. Lanes 1 and 8 contained RBPs prior to Rotofor fractionation. Lanes 2-7 contained Rotofor compartment fractions 14-9, respectively).