Determination of the Isoelectric Point of Proteins by Capillary Isoelectric Focusing (CAT#: STEM-ET-0363-ZJF)

Introduction

Isoelectric focusing (IEF) is an electrophoretic technique by which amphoteric compounds are fractionated according to their isoelectric points (pI) along a continuous pH gradient. Contrary to zone electrophoresis, where the constant (buffered) pH of the separation medium establishes a constant charge density at the surface of the molecule and causes it to migrate with constant mobility (in the absence of molecular sieving), the surface charge of an amphoteric compound in IEF keeps changing, and decreasing, according to its titration curve, as it moves along a pH gradient until it reaches its equilibrium position, i.e. the region where the pH matches its pI. There, its mobility equals zero and the molecule comes to a stop. This service provides a method for determining isoelectric points (pI) of proteins in capillary isoelectric focusing.