Ion Exchange Chromatography (IEC) - A gradient driven separation based on the charge of the protein and its relative affinity for the chemical spine of the column. Previous to reaching their pI, protein mobility also relies upon upon dimension, conformation, steepness of pH gradient, and the voltage gradient. The protein can be eluted amino acids supplier in China a reducing salt gradient, with probably the most hydrophobic proteins eluting from the column final. Two-dimensional Gel Electrophoresis - A type of electrophoresis by which proteins are separated first in one direction by charge followed by a measurement separation in the perpendicular direction.