Analogues and fragments of secretin.

For the purpose of analytical investigation and structure/activity relationships, some secretin analogues and secretin fragments have been synthesized. HPLC comparison of the synthesized products with our synthetic secretin revealed about 2% [D-Ala17]secretin, 1% [D-Leu13]secretin and less than 1% aminoterminal degradation products. The D-Ala17 content can be eliminated if the starting material used for segment coupling (Z-Arg(Z2)-Asp(OBut)-Ser(But)-Ala-OH) has no D-Ala-contamination. In addition, traces of the rearrangement products [3-aspartoyl]-secretin and [beta-Asp3]secretin are suspected. Secretin can be degraded to several compounds by chromatography on a strong basic ion exchanger in 1% acetic acid. These products are more polar than secretin and have no biological activity. The secretin content measured by HPLC correlated well with the biological data, since the degradation products and other byproducts separated by HPLC have only a negligible influence on the pancreatic flow.