PLG and cystic fibrosis: This present study details the preparation of additional examples of this ABP chemotype (see Figure 2 for structures), discusses their inhibitory activity and illustrates their use in the detection/disclosure of a broad range of serine proteases including trypsin, chymotrypsin, cathepsin G, neutrophil elastase (NE), the trypsin-like protease plasmin, and demonstrates the use of the NE-directed ABP for the detection of active forms of this protease in samples obtained from patients with cystic fibrosis.