Binding of protein S to phospholipid surfaces. Protein S (0-120nM) was incubated in a plate coated with 25 μg/mL phospholipids. Bound protein S was detected with an HRP-conjugated polyclonal antibody against protein S. A representative experiment is shown. The apparent Kd values, 5.69 ± 1.24 and 9.54 ± 2.26nM for WT protein S and protein S D95A, respectively, were obtained by calculating the mean ± SD of 3 independent experiments performed in duplicate. PL indicates phospholipids.