Combination of two-dimensional gel electrophoresis with microsequencing and amino acid composition analysis: improvement of speed and sensitivity in protein characterization.

High-resolution two-dimensional polyacrylamide electrophoresis (2-DE) is commonly used as an analytical approach to resolve and detect most of the numerous protein species of an organism. However, the isolation of microgram amounts of protein in a 2-DE spot in a form suitable for microsequence analysis and amino acid composition analysis is a key step in the chemical characterization of these proteins. With the development of chemically inert membranes it is now possible to retain proteins present in low quantities from the polyacrylamide matrix with high yields. The immobilized proteins are suitable for direct sequence analysis and amino acid composition analysis. The combination of protein chemical and electrophoretic techniques makes it possible to obtain chemical information from subpicomole quantities of protein, resulting in the availability of a new set of biologically important proteins for structural analysis. This paper summarizes the methods and strategies for the chemical protein analysis of 2-DE spots in our laboratory.