1] Measurement of molecular weights by electrophoresis on SDS-acrylamide gel

Abstract

This chapter describes methods for sodium dodecyl sulfate (SDS) gel electrophoresis and the characterization of proteins separated on SDS gels. SDS dissociates proteins into their constituent polypeptide chains. Polyacrylamide gel electrophoresis in the presence of SDS separates polypeptide chains according to their molecular weights. Thus, the size of the polypeptide chains of a given protein can be determined by comparing their electrophoretic mobilities on SDS gels to the mobilities of marker proteins with well-characterized polypeptide chain molecular weights. SDS-polyacrylamide gel electrophoresis is easily and rapidly performed, requires only inexpensive equipment, and can be used with microgram amounts of protein. The technique is both reliable and reproducible, and the results are easy to interpret. The procedure described in the chapter is designed to alkylate various functional groups of the proteins so as to maximize the likelihood of irreversible denaturation. Small changes in electrophoretic mobility may occur after such extensive alkylation.