Gel electrophoresis is an important methodology employed for protein analysis. It is often necessary to elute and recover proteins separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The procedure involves localizing the protein of interest on the gel following SDS-PAGE, eluting the protein from the gel, removing SDS from the eluted sample, and finally renaturing the protein (enzymes, for example) for subsequent analysis. Proteins are extracted from gels by several methods. These include dissolution of the gel matrix, passive diffusion, and electrophoretic elution. Proteins eluted from gels have been used successfully in a variety of downstream applications, including protein chemistry, proteolytic cleavage, determination of amino acid composition, polypeptide identification by trypsin digestion and matrix-assisted laser desorption ionization-time of flight mass spectroscopy, as antigens for antibody production, identifying a polypeptide corresponding to an enzyme activity and other purposes. Protein yields ranging from nanogram levels to 100 μg have been obtained.