PhastSystem IEF gel electrophoresis of RBPs containing a pH 4-6.5 gradient. The gel was run at 2000 V limiting, 3.5 W and 5 mA for 654 Vh following 75 Vh of prefocusing at 2 mA. Three µg protein was applied to both the anode and cathode and stained with Coomassie Blue. Lanes 1 and contain low pI calibration markers; RBPs following Sephadex G-75 fractionation are in lane 2; RBPs after fractionation in a Rotofor cell are in lane 3.