Characterization of linear and cyclic glucagon analogs by fast atom bombardment mass spectrometry

Fast atom bombardment mass spectral mapping of endoproteinase Asp-N digest mixtures is used for characterization of new synthetic linear and cyclic glucagon analogs. The results allow rapid identification of sequence modifications in linear glucagon analogs. For the cyclic compounds, the technique allows confirmation of the presence and position of the cyclic amide bond, as well as verification of the sequence of the modified glucagon analogs. The specificity of the Asp-N enables differentiation of isometric glucagon analogs which differ only in the position of the cyclic amide bond. Important information concerning the purity of the synthetic analogs is also available.