Conformational Properties of Aβ Peptide Oligomers in Aqueous Ionic Liquid Solution: Insights from Molecular Simulation Studies.

Alzheimer's disease is a progressive irreversible neurological disorder with abnormal extracellular deposition of amyloid β (Aβ) peptides in the brain. We have carried out atomistic molecular dynamics simulations to investigate the size-dependent conformational properties of aggregated Aβ oligomers of different orders, namely, pentamer [O(5)], decamer [O(10)], and hexadecamer [O(16)] in aqueous solutions containing the ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF]). The calculations revealed reduced peptide conformational fluctuations in O(5) and O(10) in the presence of the IL.

Exploring the Heterogeneous Dynamical Environment at the Interface of Aβ Peptide in Aqueous Ionic Liquid Solution.

In this study, we have investigated the heterogeneous dynamical environment around an ensemble of full-length amyloid-β (Aβ) peptide monomers in binary aqueous solution containing the ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF] as a co-solvent. Atomistic molecular dynamics (MD) simulations have been employed with the aim of understanding the effect of the IL on the distribution of water molecules and IL components around distinct segments of the peptide. As compared to pure aqueous medium, locally heterogeneous restricted water motions at the interface have been spotted in the presence of the IL.

Dynamical properties across different coarse-grained models for ionic liquids.

Room-temperature ionic liquids (RTILs) stand out among molecular liquids for their rich physicochemical characteristics, including structural and dynamic heterogeneity. The significance of electrostatic interactions in RTILs results in long characteristic length- and timescales, and has motivated the development of a number of coarse-grained (CG) simulation models. In this study, we aim to better understand the connection between certain CG parameterization strategies and the dynamical properties and transferability of the resulting models.

Microscopic Understanding of the Effect of Ionic Liquid on Protein from Molecular Simulation Studies.

We have performed molecular dynamics (MD) simulations of the protein α-lactalbumin in aqueous solution containing the ionic liquid (IL) 1-butyl-3-methyl imidazolium tetrafluoroborate ([BMIM][BF]) as the cosolvent at different concentrations. Attempts have been made to obtain quantitative understanding of the effects of the IL on the conformational features of the protein as well as the distributions of the IL and water around it. The calculations revealed enhanced rigidity of the protein with reduced conformational fluctuations and increasingly correlated local motions in the presence of the IL.

On the relevance of electrostatic interactions for the structural relaxation of ionic liquids: A molecular dynamics simulation study.

We perform molecular dynamics simulations to investigate the structural (α) relaxation of models of 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF]) room temperature ionic liquids. To determine the relevance of electrostatic interactions for the dynamical properties, we systematically scale the partial charges of the ions. Observing the structural relaxation of these charge-scaled ionic liquids from high temperature far above the melting point to low temperatures in the viscous regime, we find that the α-relaxation times τ strongly depend on the strength of the electrostatic interactions.

Role of Dynamic Heterogeneities in Ionic Liquids: Insights from All-Atom and Coarse-Grained Molecular Dynamics Simulation Studies.

We performed molecular dynamics simulations for the room-temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF ]). By employing all-atom (AA) and coarse-grained (CG) models, we compared the characteristic times of various dynamical modes, from vibration to diffusion, and the importance of dynamical heterogeneities at different levels of chemical resolution and over broad temperature ranges. It was shown that coarse graining leads to a substantial speedup in molecular dynamics, whereas it weakly affects the strength of dynamical heterogeneities.

Composition Dependence of Dynamic Heterogeneity Time- and Length Scales in [Omim][BF4]/Water Binary Mixtures: Molecular Dynamics Simulation Study.

Composition dependence of four-point dynamic susceptibilities, overlap functions, and other dynamic heterogeneity (DH) parameters have been investigated by using all-atom molecular dynamics simulations for aqueous solutions of the ionic liquid (IL), 1-octyl-3-methyl imidazolium tetrafluoroborate ([Omim][BF4]) covering the pure-to-pure range. Upon addition of water in the IL, the DH time scales become faster and the four-point dynamic susceptibility time scale softens. Evidences for jump motions for both water and ions have been found from the simulated single particle displacements that show strong deviation from Gaussian distribution.

Stokes shift dynamics in (non-dipolar ionic liquid + dipolar solvent) binary mixtures: a semi-molecular theory.

A semi-molecular theory for studying composition dependent Stokes shift dynamics of a dipolar solute in binary mixtures of (non-dipolar ionic liquid + common dipolar solvent) is developed here. The theory provides microscopic expressions for solvation response functions in terms of static and dynamic structure factors of the mixture components and solute-solvent static correlations. In addition, the theory provides a framework for examining the interrelationship between the time dependent solvation response in and frequency dependent dielectric relaxation of a binary mixture containing electrolyte.

Slow solvation in ionic liquids: connections to non-Gaussian moves and multi-point correlations.

This paper explores an interconnection between timescales of dynamic heterogeneity (DH) in a neat ionic liquid (IL), 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]), and slow solvation of a dipolar solute, coumarin 153 (C153) in it at 298 K and 450 K. Molecular dynamics simulations employing realistic interaction potentials for both the IL and the solute have been performed. DH timescales have been obtained from non-Gaussian and new non-Gaussian (NNG) parameters, and four-point dynamic susceptibilities (χ4(k, t)) and overlap functions (Q(t)).

Stokes shift dynamics of ionic liquids: solute probe dependence, and effects of self-motion, dielectric relaxation frequency window, and collective intermolecular solvent modes.

In this paper we have used a semi-molecular theory for investigating the probe dependence of Stokes shift dynamics in room temperature ionic liquids (ILs) by considering three different but well-known dipolar solvation probes--coumarin 153, trans-4-dimethylamino-4(')-cyanostilbene, and 4-aminophthalimide. In addition, effects on polar solvation energy relaxation in ILs of solute motion, frequency coverage (frequency window) accessed by dielectric relaxation measurements and collective IL intermolecular modes (CIMs) at tera-hertz range have been explored. Eleven different ILs have been considered for the above theoretical study.