Disassembly Of Allomelanin Nanoparticles In Solution: A Molecular Dynamics Simulation Study
Date
2022-05
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
Allomelanin, a naturally occurring nitrogen-free melanin, can be synthetically
produced from the polymerization of 1,8-dihydroxynapthalene (DHN) precursor
molecule to form spherical nanoparticles. Recent experiments have shown that the
structure of synthetic allomelanin nanoparticles can be altered by subjecting the
nanoparticle to different organic solvents. To determine the molecular forces impacting
the structure of these nanoparticles in different organic solvents, we used atomistic
molecular dynamics (MD) simulations to study both the assembly of three isomers of
DHN dimers in explicitly represented water molecules, and the disassembly of these
aggregates in explicitly represented organic solvent (methanol, acetic acid, and ethyl
acetate) molecules. We analyzed the structure of the aggregate as it disassembled and
the dynamics of disassembly. We also identified the intermolecular forces that
contribute to the structure and disassembly. Aggregates of DHN44 were found to be
more anisotropic than DHN22 or DHN24, likely contributing to DHN44 aggregates’
faster rate of disassembly. All aggregates exhibited the fastest rates of disassembly in
methanol, followed by ethyl acetate, and then acetic acid. We found that the disruption
of dimer-dimer hydrogen bonds and formation of dimer-solvent hydrogen bonds is the
largest contributing factor to the disassembly of the dimer aggregate; the solvent size,
polarity, and ability to form hydrogen bonds with aggregated dimers affect the solvent
diffusion and formation of dimer-solvent hydrogen bonds.
Description
Keywords
Allomelanin, Molecular dynamics, Organic solvents