Exploring the frontiers of synthetic eumelanin polymers by high-resolution matrix-assisted laser/desorption ionization mass spectrometry

"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 highmass limits, giving at the same time information. on the polymerisationmode, 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 theway. to the production of N-functionalized, synthetic eumelanin-inspired soft materials, for possible future technological applications"