Ascione, Laura;
Pezzella, Alessandro;
Ambrogi, Veronica;
Carfagna, Cosimo;
d'Ischia, Marco
Intermolecular π‐Electron Perturbations Generate Extrinsic Visible Contributions to Eumelanin Black Chromophore in Model Polymers with Interrupted Interring Conjugation
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Media type:
E-Article
Title:
Intermolecular π‐Electron Perturbations Generate Extrinsic Visible Contributions to Eumelanin Black Chromophore in Model Polymers with Interrupted Interring Conjugation
Published in:
Photochemistry and Photobiology, 89 (2013) 2, Seite 314-318
Language:
English
DOI:
10.1111/php.12003
ISSN:
0031-8655;
1751-1097
Origination:
Footnote:
Description:
<jats:title>Abstract</jats:title><jats:p>The key structural factors underlying the unique black chromophore of eumelanin biopolymers have so far defied elucidation. Capitalizing on the ability of 1% polyvinylalcohol (PVA) to prevent pigment precipitation during melanogenesis <jats:italic>in vitro</jats:italic>, we have investigated the visible chromophore properties of soluble eumelanin‐like polymers produced by biomimetic oxidation of 5,6‐dihydroxyindole (DHI) and 5,6‐dihydroxyindole‐2‐carboxylic (DHICA) in 1% PVA‐containing buffer at pH 7. Upon dilution DHI‐eumelanin solutions exhibited almost linear visible absorbance changes, whereas DHICA‐eumelanin displayed a remarkable deviation from linearity in simple buffer, <jats:italic>but not</jats:italic> in PVA‐containing buffer. It is suggested that in DHICA polymers, exhibiting repeated interruptions of interring conjugation due to lack of planar conformations, the black chromophore is not due to an overlap of static entities defined intrinsically by the conjugation length across the carbon frame, but results largely from aggregation‐related <jats:italic>intermolecular</jats:italic> perturbations of the π‐electron systems which are extrinsic in character.</jats:p>