Binding of WT protein S and protein S/Gas6 chimeras I to III to TFPI studied with SPR. A CM5 chip was coupled with TFPI immobilized to 2500 response units. The flow cell was perfused with increasing concentrations (0-1000 nM) of WT protein S (A), protein S chimera I (B), protein S chimera II (C), or protein S chimera III (D). Results from a representative experiment are shown (n = 2). PS, protein S; RU, response units.