Two-dimensional electrophoresis (2-DE) is potentially the most powerful technique known for resolving complex protein mixtures. Proteins can be purified to homogeneity in one step in most cases. The applications for 2-DE are numerous and diverse. They include the analysis of protein patterns in various organisms and tissues, monitoring of the purity of fractions derived from chro-matography (or other separation methods), and the determination of the characteristics of a particular protein, such as isoelectric point, molecular weight of subunits, and number of isoforms.