Conformationally constrained chemotactic peptide analogs of high biological activity.

The stereochemically constrained chemotactic peptide analogs, formylmethionyl-alpha-aminoisobutyryl-phenylalanine (formyl-Met-Aib-Phe-OH) and formylmethionylcycloleucinylphenylalanine (formyl-Met-Cyl-Phe-OH) are highly effective in inducing lysosomal enzyme release from rabbit neutrophils. NMR studies of the Aib2 analog in (CD3)2SO favor a folded conformation in which the Phe NH group is inaccessible to solvent. Intramolecularly hydrogen-bonded conformations involving a Met-Aib-beta-turn or a gamma-turn centered at Aib2 are considered. The results suggest that folded conformations may allow highly active interactions with the neutrophil formylpeptide receptor.