Disulfide linkage to polyacrylic resin for automated Fmoc peptide synthesis. Immunochemical applications of peptide resins and mercaptoamide peptides

The use of disulfide bonds for peptide–resin linkage in solid-phase peptide synthesis was investigated using polyacrylic polymers (Expansin^TM) and automated Fmoc methodology. The disulfide moiety was bound to the support either by coupling a protected bifunctional handle or by an original stepwise procedure. Among the three different disulfide handles that were investigated, only the aminoethyldithio-2-isobutyric acid (AEDI) handle was stable enough to achieve peptide synthesis. A series of peptides of up to 10–20 amino acids were prepared in this manner, in good yield and purity. Rapid and quantitative peptide release was obtained by reduction with equimolecular amounts of dithiothreitol at pH 9 or tris(2-carboxymethyl) phosphine at pH 4.5. This allowed direct and rapid coupling of the released cysteamide peptides to an activated protein carrier and the use of free or resin-bound forms of the antigen in immunoassays.