Methods for obtaining peptide maps of proteins on a subnanomole scale

A rapid method of peptide mapping by thin layer electrophoresis and chromatography is described that permits good maps to be produced from as little as 0.5 nmole of protein by means of conventional staining procedures with ninhydrin. The method can be made even more sensitive by prior amidination of the protein amino groups using methyl-[1- 14C]acetimidate, a simple synthesis of which is given. Because proteins generally contain many amino groups, autoradiographs of peptide maps of such radiolabeled proteins show a large number of spots in characteristic patterns, and the derivatization of the protein is easy and specific. A cheap and simply constructed apparatus for carrying out the thin layer electrophoresis is also described.