MDNCF is a human monocyte-derived, 72-residue chemotactic peptide, which has sequence similarity with members of a family of pro-inflammatory cytokines. The peptide was synthesized by the solid-phase method, and is identical to the natural peptide in amino acid composition, sequence and chemotactic potency. MDNCF forms two loops via a neighboring pair of disulfide bridges, the probable locations of which are residues 7–34 and 9–50. Reduction and alkylation eliminated chemotactic activity. MDNCF fragments 7–37, 30–72 and 17–72 were all biologically inactive. The data suggest that the region of the clustered pair of disulfide bridges is important for biological activity.
