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Title: Thermodynamics, morphology, and kinetics of early-stage self-assembly of π-conjugated oligopeptides

Synthetic oligopeptides containing π-conjugated cores self-assemble novel materials with attractive electronic and photophysical properties. All-atom, explicit solvent molecular dynamics simulations of Asp-Phe-Ala-Gly-OPV3-Gly-Ala-Phe-Asp peptides were used to parameterize an implicit solvent model to simulate early-stage self-assembly. Under low-pH conditions, peptides assemble into β-sheet-like stacks with strongly favorable monomer association free energies of ΔF ≈ -25kBT. Aggregation at high-pH produces disordered aggregates destabilized by Coulombic repulsion between negatively charged Asp termini (ΔF ≈ -5kBT). In simulations of hundreds of monomers over 70 ns we observe the spontaneous formation of up to undecameric aggregates under low-pH conditions. Modeling assembly as a continuous-time Markov process, we infer transition rates between different aggregate sizes and microsecond relaxation times for early-stage assembly. Our data suggests a hierarchical model of assembly in which peptides coalesce into small clusters over tens of nanoseconds followed by structural ripening and diffusion limited aggregation on longer time scales. This work provides new molecular-level understanding of early-stage assembly, and a means to study the impact of peptide sequence and aromatic core chemistry upon the thermodynamics, assembly kinetics, and morphology of the supramolecular aggregates.
Authors:
Publication Date:
Grant/Contract Number:
SC0004857
Type:
Accepted Manuscript
Journal Name:
Molecular Simulation
Additional Journal Information:
Journal Volume: 42; Journal Issue: 12; Journal ID: ISSN 0892-7022
Publisher:
Taylor & Francis
Research Org:
Univ. of Illinois, Urbana-Champaign, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Contributing Orgs:
Molecular simulations were partially conducted on University of Illinois Computational Science and Engineering Program parallel computing resources, which are supported by the University of Illinois.
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; π-conjugated oligopeptides; molecular dynamics simulation; supramolecular peptides; self-assembly; Markov state model
OSTI Identifier:
1357188
Alternate Identifier(s):
OSTI ID: 1357187