Fluorescent Analogues of the Insect Neuropeptide Helicokinin I: Synthesis,Photophysical Characterization and Biological Activity

In insects numerous physiological processes are regulated by neuropeptides. Two fluorescent analogues of the amino acids tryptophan and tyrosine were synthesized and incorporated in the diuretic neuropeptide helicokinin I from the moth Heliothis zea. By fluorescence emission measurements it was shown that both fluorescent helicokinin I analogues react sensitive on the dielectricity of their microenvironment. A helicokinin I analogue containing the fluorescent tryptophan mimic β-[6'-(N,N-dimethyl)-amino-2'-naphthoyl]alanine (Ald) was shown to bind to dodecylphosphocholine (DPC) micelles by the Ald residue. A membrane binding model for helicokinin I is proposed based on data from related mammalian and insect-neuropeptides.