Design and biological activity of a new generation of synthetic C3a analogues by combination of peptidic and non-peptidic elements.

Based on published X-ray crystallographic data of the anaphylatoxic complement peptide C3a, we have synthesized a series of peptides with appropriate amino acid exchanges and a maximal length of 13 amino acids. N-terminal acylation of these optimized structures with epsilon-aminohexanoic acid and complex aromatic structures like fluorenylmethoxycarbonyl, 2-nitro-4-azidophenyl, fluoresceinyl and rhodaminyl leads to a dramatic increase in biological activity. The culmination of our synthetic efforts is a C3a analogue with 13 amino acid residues and a biological activity six times that of native C3a.