Intramol. O,N-acyl migration reactions were used as structural switch (S-elements) from a depsipeptide bond contg., unfolded state (Soff) to an all-amide, native states (Son). Chem. or enzymically triggered acyl migrations allowed for the controlled induction of folding events in the process of primary structure evolution, i.e., in statu nascendi (ISN) of the native mol. In the (Soff)-state, the switch-peptide contg. two enzyme (dipeptidyl peptidase IV and pyroglutamate aminopeptidase) cleavable S-elements proved to be highly sol. at physiol. conditions, thus facilitating HPLC purifn. and structural characterization. The conformational decoupling of the individual peptide blocks resulted in a flexible random coil conformation, showing no tendency for self-assocn. or fibril formation after 24 h. In contrast, after selective triggering of the acyl migrations, significant changes in the physicochem. and conformational properties paralleled by the onset of Abeta-like fibrils were obsd.