Nature und Extent of Peptide Bond Cleavage by Anhydrous Heptafluorobutyric Acid during Edman Degradation

Abstract

During the isothiocyanate degradation of proteins a gradual increase in the level of all thiohydantoin derivatives of amino acids occurs, which progressively obscures the sequential identification of the significant N-terminal amino acids. The major cause for this was a hitherto unknown specific cleavage at aspartic acid residues in anhydrous heptafluorobutyric acid and to a lesser extent, the N .fwdarw. O shift in peptide bonds involving hydroxyamino acids. Measures to reduce susceptibility of the peptide bonds at these sites are described.