Intermolecular pi-Electron Perturbations Generate Extrinsic Visible Contributions to Eumelanin Black Chromophore in Model Polymers with Interrupted Interring Conjugation
| Autor: | Marco d'Ischia, Veronica Ambrogi, Alessandro Pezzella, Laura Ascione, Cosimo Carfagna |
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| Přispěvatelé: | L., Ascione, Pezzella, Alessandro, Ambrogi, Veronica, Carfagna, Cosimo, D'Ischia, Marco |
| Jazyk: | angličtina |
| Rok vydání: | 2013 |
| Předmět: |
Indoles
Ultraviolet Rays Electrons Electron Photochemistry OXIDATION Biochemistry Absorbance chemistry.chemical_compound Pigment Biopolymers OLIGOMERS BIOMIMETIC CONDITIONS Physical and Theoretical Chemistry chemistry.chemical_classification Melanins Precipitation (chemistry) Intermolecular force DHICA General Medicine Polymer Chromophore ABSORPTION PROPERTIES Hydrogen-Ion Concentration PRECURSOR 5 POLYMERIZATION chemistry 6-DIHYDROXYINDOLE-2-CARBOXYLIC ACID BIOMIMETIC CONDITIONS ABSORPTION PROPERTIES OXIDATION POLYMERIZATION OLIGOMERS visual_art Polyvinyl Alcohol visual_art.visual_art_medium 6-DIHYDROXYINDOLE-2-CARBOXYLIC ACID Oxidation-Reduction |
| Popis: | 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 in vitro, 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 acid (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, but not 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 intermolecular perturbations of the π-electron systems which are extrinsic in character. |
| Databáze: | OpenAIRE |
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