Intermolecular Association of Some Selected Melanin Monomers and Their Optical Absorption

Publication date: Available online 5 February 2019Source: Computational and Theoretical ChemistryAuthor(s): Subhrangshu Supakar, Aulie Banerjee, Tarun JhaAbstractMelanin is a black-brown pigment with varied functions found widely distributed in living bodies across the globe. The exact molecular structure is still debatable/undefined and is considered to be formed by polymerization of 5,6-dihydroxyindole (DHI), 5,6- dihydroxyindole carboxylic acid (DHICA) and their quinonoid products. For eumelanin, an oligomeric view is proposed in this article where the protomolecules are in stacked conformation and comprises of the hydroxyindole/quinoneindole units. Molecular dynamics simulation analyses were performed on different homo- and heteromeric systems/ensembles of the monomeric units that revealed their tendency towards aggregation/(near) stacking through intermolecular interactions. It was observed that systems exhibiting such interactions produce UV-visible spectra different from that of a single monomeric unit. Due to aggregation/(near) stacking, the DHICA systems were observed to have maximum UV-visible absorption in the shorter wavelength region (200-500 nm) and the DOICA (5,6- quinoneindole carboxylic acid) systems in the longer wavelength region (500-800 nm). The heteromolecular systems with such interactions produced significantly altered (broadened) UV-visible spectra with relatively greater absorption in the higher energy region. The study may provide an insight on the ...
Source: Computational and Theoretical Chemistry - Category: Chemistry Source Type: research
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