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Exploring the frontiers of synthetic eumelanin polymers by high‐resolution matrix‐assisted laser/desorption ionization mass spectrometry
Author(s) -
Reale Samantha,
Crucianelli Marcello,
Pezzella Alessandro,
d'Ischia Marco,
De Angelis Francesco
Publication year - 2012
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/jms.2025
Subject(s) - chemistry , polymerization , mass spectrometry , desorption , matrix assisted laser desorption/ionization , polymer , combinatorial chemistry , nanotechnology , organic chemistry , chromatography , materials science , adsorption
New trends in material science and nanotechnologies have spurred growing interest in eumelanins black insoluble biopolymers derived by tyrosinase‐catalysed oxidation of tyrosine via 5,6‐dihydroxyindole (DHI) and its 2‐carboxylic acid (DHICA). Efficient antioxidant and photoprotective actions, associated with peculiar optoelectronic properties, are recognised as prominent functions of eumelanin macromolecules within the human and mammalian pigmentary system, making them unique candidates for the realisation of innovative bio‐inspired functional soft materials, with structure‐based physical–chemical properties. An unprecedented breakthrough into the mechanism of synthetic eumelanin buildup has derived from a detailed investigation of the oxidative polymerization of DHI and its N‐methyl derivative (NMDHI) by linear and reflectron matrix‐assisted laser/desorption ionization mass spectrometry. Regular collections of oligomers of increasing masses, spanning the entire m/z ranges up to 5000 Da (>30‐mer) and 8000 Da (> 50‐mer) for the two building blocks, respectively, were disclosed. It is the first time that the in vitro polymerisation of dihydroxyindoles to form synthetic eumelanins is explored up to its high mass limits, giving at the same time information on the polymerisation mode, whether it follows a stepwise pattern (being this the conclusion in our case) or a staking sequencing of small‐sized entities. It also highlighted the influence of the N‐methyl substituent on the polymerization process; this opens the way to the production of N‐functionalized, synthetic eumelanin‐inspired soft materials, for possible future technological applications. Copyright © 2012 John Wiley & Sons, Ltd.