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Melanins from opioid peptides

M A Rosei1

  • 1Dipartimento di Scienze Biochimiche, Roma, Italia. rosei@axcasp.caspur.it

Pigment Cell Research
|December 1, 1996
PubMed
Summary

Synthetic opiomelanins, derived from opioid peptides, are soluble and stable pigments. Their unique properties, including altered electron transfer and UV-VIS spectra, suggest potential roles in biological systems.

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Area of Science:

  • Biochemistry
  • Materials Science
  • Biophysics

Background:

  • Opioid peptides and Tyr-NH2-terminal peptides serve as substrates for tyrosinase.
  • Tyrosinase catalyzes the formation of melanins from tyrosine-based substrates.

Purpose of the Study:

  • To synthesize and characterize melanins derived from opioid peptides (opiomelanins).
  • To investigate the physicochemical and spectroscopic properties of opiomelanins.
  • To explore the stability and potential biological relevance of these novel melanins.

Main Methods:

  • In vitro enzymatic synthesis of melanins using mushroom and sepia tyrosinase.
  • Characterization of melanins using solubility tests, EPR spectroscopy, UV-VIS spectroscopy, and stability assays.
  • Incorporation of opioid peptides into Dopa-melanin to form mixed-type pigments.

Main Results:

  • Opiomelanins exhibit complete solubility in hydrophilic solvents at neutral and basic pH.
  • Spectroscopic analysis reveals unique UV-VIS absorption peaks (e.g., 330 nm) and paramagnetism similar to Dopa-melanin.
  • The linked peptide chain significantly influences electron transfer properties and oxidizing activity, with Enk-melanin showing no oxidizing activity.
  • Opiomelanins demonstrate stability at neutral/basic pH but are degraded by H2O2 and photodegradation under solar illumination.

Conclusions:

  • Opiomelanins are a novel class of synthetic melanins with distinct physicochemical properties.
  • The incorporation of peptide moieties alters melanin characteristics, impacting electron transfer and stability.
  • These findings suggest potential roles for opiomelanins in biological contexts and materials science.

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