Structural Transformation of the Peptide Fragments from the Reactive Center Loops of Serpins: Circular Dichroic Studies

Abstract

AbstractTwo peptides, derived from the reactive center of ovalbumin (OVARC) and plasminogen activator inhibitor‐1 (PAIRC) respectively were chemically synthesized and investigated by circular dichroic spectroscopy. The secondary structural transformation in solution and in solid state was studied. OVARC shows a nascent helical structure in aqueous solution, and its helical content increases under acidic conditions. There is no obvious structural conversion from solution to solid state. PAIRC, however, undergoes a structural transformation from random coil in aqueous solution to a typical β‐sheet structure in the solid state. Hexafluoroisopropanol (HFIP) prompts helical structures of the two peptides in solution, but it seems to trigger the structural formation of β‐sheets in solid state. The novel structural transformation from random coil or nascent helical structure in aqueous solution to the α‐helix in HFIP and to the β‐sheet structure in solid state may reflect the conformational polymorphism of the serpin reactive centers and is implicated in the structural features of the amyloid aggregates.