Apoptotic activity of Aα-chain fragments. Adherent JEG3 cells were incubated in the absence (control) or presence of 1 mM (■) or 2 μM () synthetic peptides or recombinant E coli protein for 48 hours, and apoptosis was determined by TUNEL assay. (A) RGD-independent apoptotic bioactivity resides in Aα17-83. (B) Aα17-37 is sufficient to induce apoptosis at 1 mM concentration; the amino-terminal glycine residue comprising the neo-epitope generated after release of FPA from fibrinogen is necessary for apoptotic bioactivity. scr: sequence scrambled control. Bars represent the average plus or minus SE from 3 independent experiments with 3 measurements each. *P < .05 by Student t test.