The antibacterial activity of HNP1 preparations was evaluated using Staphylococcus aureus 502a as the test organism employing a microbicidal assay format described previously [46] . Briefly, log phase cultures of S. aureus (,1610 4 CFU/ml) were suspended in 100 ml buffer (20 mM Tris pH 8.0, 28 mM NaCl) plus 0.03% TSB with dilutions of HNP1 ranging from 0 to 8 mg/ml in 0.01% acetic acid for 2 h at 37uC. Aliquots were plated on TSB plates and colonies were counted after overnight incubation at 37uC. Native HNP1 from human leukocytes was used as control. The source of human leukocytes was discarded, de-identified buffy coat preparations from The University of California Irvine-Medical Center clinical labs. Figure S1 Folding of His 6 -proHNP1B. His 6 -proHNP1A and His 6 -proHNP1B were analyzed by C18 RP-HPLC and AU-PAGE. Shown are chromatograms and corresponding Coomassie stained gels of His 6 -proHNP1A and His 6 -proHNP1B analyzed A) without additional treatment, B) after 4 h incubation in TUN buffer alone, and C) after 4 h incubation in TUN buffer supplemented with reduced and oxidized glutathione. (TIF)