Amino-Acid Composition and Gas-Phase Sequence Analysis of Proteins and Peptides from Glass Fiber and Nitrocellulose Membrane Electro-Blots

Abstract

For proteins which can only be isolated in very small amounts, gas-phase sequencing [1, 2] has become an essential tool in the field of molecular genetics and biotechnology. This is true for the elucidation of complete structures, as well as for the identification of amino-acid sequence stretches in order to design suitable oligonucleotide probes. In addition, sequencing of small amounts of proteins will become of increasing importance in establishing postsynthetic protein modifications, identification of epitopes, and in general structure function relationship, to name a few. In order to perform the structural characterizations of proteins and peptides, these have to be isolated in pure form, a process which in most cases is the most time-consuming step. Powerful analytical methodology for proteins has been developed in many laboratories over the last decade in the form of the numerous variants of polyacrylamide gel electrophoresis. In this field the arsenal of identification methods for the fractions separated electrophoretically has been considerably enlarged by the introduction of Western blotting techniques [3, 4]. Replacing the nitrocellulose membrane in such methodology with the more inert glass microfiber filter as the adsorbing material in the transfer opens the way to subjecting proteins and peptides separated electrophoretically on an analytical scale directly to amino-acid and sequence analysis.