Although electrostatics interactions in fluids have been studied for many decades, new results in this field are still challenging our classical understanding of electrolytes. The combination of electrostatics and self-assembly yields many interesting yet challenging problems that are of fundamental scientific interest and show promise for industrial applications. In this dissertation, I introduce our work on the topic of charged nanomaterials in aqueous salt solutions and how electrostatics play a role in different systems. The work summarized here is an attempt to develop methods to correctly model nanoscale charged systems in both low and high salt environments, and tackle the problem of simulating large systems with MD simulations by using coarse-graining techniques. First, we study nanoparticles immersed in concentrated monovalent salt (0.5 mol/L (the unit mol/L is also written as M for short)) using multi-scale molecular dynamics (MD) simulations involving atomic resolution and coarse-grained representations with implicit solvent. We find a surprising attractive to repulsive and then attractive re-entrant behavior as a function of salt concentration that cannot be predicted by previous theories and propose a rational explanation. Next, we explore the interaction of cylindrical interfaces in NaCl solutions to find the screening length of charged cylinders and compare them with the prediction of the Poisson-Boltzmann (PB) equation. We also find a depletion attraction between cylinders at high monovalent salt concentrations. We compare the results of MD simulations to mean-field theories as well as liquid state theory that incorporates ion correlations, and we show that the short-range ion correlations significantly impact the interactions between cylinders in concentrated monovalent salt solutions. Finally, we look into the complex biological system of bacterial microcompartment (MCP) assembly. Using all-atom (AA, explicit water, and ion) and coarse-grained (CG, implicit ion) MD simulations, combined with thermodynamics analysis, we find that electrostatic interactions (hydrogen bonds and charge distributions) play an important role in the self-assembly of native propanediol utilization (Pdu) MCPs. Combining AA and CG MD simulations, we predict various polyhedral and extended assembly shapes, and we predict what kinds of mutations lead to the success or failure of MCP assembly. The simulation and theoretical predictions match with the experimental observation of our collaborators and with published experiments.

Creator

• Li, Yaohua

DOI

• https://doi.org/10.21985/n2-ef3a-kn59

Subject

• Physical chemistry
• Physics

Language

• en

Alternate Identifier

• etdadmin_upload_794957
• http://dissertations.umi.com/northwestern:15462

Keyword

• Polyelectrolyte
• Salt
• Nanoparticle
• Bacterial Microcompartments
• Molecular Dynamics
• Electrostatics

Date created

• 2021-01-01

Resource type

• Dissertation

Rights statement

• In Copyright