Effect of PF-4 on NAP-2 formation by purified chymotryptic proteases. Purified human neutrophil cathepsin G (500 ng/mL), human mast cell chymase (250 ng/mL), or bovine pancreas chymotrypsin (200 ng/mL) was incubated with 3 μM CTAP-III alone or in the presence of 4 μM PF-4 for 30 minutes at 37°C. Thereafter, 2μL of each sample was subjected to SDS-PAGE and Western blotting and subsequently stained in sequence with Rα-βTG and IRDye 800–conjugated goat α-rabbit antiserum. NAP-2 was then quantified by Li-cor analysis against a standard of NAP-2 run in parallel. Data represent mean ± SD from 3 independent experiments.