Fig. 1.

Neutrophil-mediated oxidation of bacterial methionines. Bacteria were incubated with neutrophils for 1 h, recovered, and analyzed by LC-ESI-MS/MS. The fraction of bacterial methionine residues in peptides recovered as sulfoxides was monitored as M + 16. Abbreviations: Ctrl, PMN—nonphagocytic conditions (serum and divalent cations omitted [all PMN donors combined]); nl PMN, normal donor PMN—phagocytic conditions (serum and divalent cations present); CGD, neutrophils defective in H₂O₂ production (isolated from an individual with chronic granulomatous disease, deficient in NADPH oxidase); MPOd, PMN lacking MPO (from an individual with complete hereditary MPO deficiency); PMN+AZ, normal PMN supplemented with, 10⁻⁴ M sodium azide, an MPO inhibitor; low Cl, normal PMN, chloride salts in suspension medium replaced with gluconates. Legend parentheses indicate replicates for each condition. (A) Escherichia coli, strain ATCC11775. (B) Staphylococcus aureus, strain 502A.