FIG 2 .

PQS induces RBC hemolysis. Washed RBCs were exposed to various amounts of PQS for 30 min at room temperature. Intact cells were removed by centrifugation, and hemoglobin release was assessed by measuring the absorbance of the supernatant at 543 nm. Results are presented as percent hemolysis relative to that of a hypotonic-lysis control where RBCs were lysed by resuspension in 10 mM Tris, pH 7.5. Each point represents the average of three independent measurements ± the standard error. HHQ, 2-heptyl-4-quinolone.