Role of Counterions in Constant-pH Molecular Dynamics Simulations of PAMAM Dendrimers.

ACS Omega

Centro de Química e Bioquímica, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal.

Published: February 2018

Electrostatic interactions play a pivotal role in the structure and mechanism of action of most biomolecules. There are several conceptually different methods to deal with electrostatics in molecular dynamics simulations. Ionic strength effects are usually introduced using such methodologies and can have a significant impact on the quality of the final conformation space obtained. We have previously shown that full system neutralization can lead to wrong lipidic phases in the 25% PA/PC bilayer (. 5483-5492). In this work, we investigate how two limit approaches to the ionic strength treatment (implicitly with GRF or using full system neutralization with either GRF or PME) can influence the conformational space of the second-generation PAMAM dendrimer. Constant-pH MD simulations were used to map PAMAM's conformational space at its full pH range (from 2.5 to 12.5). Our simulations clearly captured the coupling between protonation and conformation in PAMAM. Interestingly, the dendrimer conformational distribution was almost independent of the ionic strength treatment methods, which is in contrast to what we have observed in charged lipid bilayers. Overall, our results confirm that both GRF with implicit ionic strength and a fully neutralized system with PME are valid approaches to model charged globular systems, using the GROMOS 54A7 force field.

Download full-text PDF

Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6045380PMC
http://dx.doi.org/10.1021/acsomega.7b01708DOI Listing

Publication Analysis

Top Keywords

ionic strength
16
molecular dynamics
8
dynamics simulations
8
space full
8
full system
8
system neutralization
8
strength treatment
8
conformational space
8
role counterions
4
counterions constant-ph
4

Similar Publications

The carboxymethyl chitosan (CMCS)-based porous beads are still criticized for their limited number of binding sites, which impairs their efficacy in removing aqueous pollutants. To overcome this challenge, this work introduces the production of covalently crosslinked CMCS-based beads containing SiO and poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS). The porous composite beads not only possess remarkable stability under acidic conditions, but also have abundant active binding sites for adsorption.

View Article and Find Full Text PDF

Aqueous Solubility of Sodium and Chloride Salts of Glycine─"Uncommon" Common-Ion Effects of Self-Titrating Solids.

Mol Pharm

January 2025

Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, St. John's University, 8000 Utopia Parkway, Queens, New York 11439, United States.

Although glycine is the simplest of the amino acids, its solution and solid-state properties are far from straightforward. The aqueous solubility of glycine plays an important role in various applications, including nutrition, food products, biodegradable plastics, and drug development. There is evidence that glycine in subsaturated pH 3-8 solutions forms a dimer, as suggested by several techniques.

View Article and Find Full Text PDF
Article Synopsis
  • Enhancing transport and mechanical properties in cathode composites is essential for solid-state battery performance.
  • The FAST electrode features vertically aligned carbon nanotubes in a polymer electrolyte, improving ionic and electronic conductivity while reinforcing the electrode.
  • This innovative design leads to excellent electrochemical performance, achieving a capacity of 148.2 mAh/g at 0.2 C over 100 cycles, indicating progress in solid-state lithium metal battery technology.
View Article and Find Full Text PDF

Solid polymer electrolytes (SPEs) with mechanical strength and reduced flammability may also enable next-generation Li batteries with higher energy densities. However, conventional SPEs have fundamental limitations in terms of Li conductivity. While an imidazole functionalized polymer (PMS-Im) has been previously shown to have ionic conductivity related to the imidazole-Li coordination, herein we demonstrate that quaternization of this polymer to form an analogous imidazolium functionalized polymer (PMS-Im) more efficiently solvates lithium salts and plasticizes the polymer.

View Article and Find Full Text PDF

The present investigation delves into the redox reaction between -chlorophenol (-CP) and hexacyanoferrate(III) [HCF(III)], catalyzed by Ag(I) in an alkaline environment. Findings reveal a first-order dependence on both -CP and the oxidant, and the reaction rate showcased a first-order reaction towards Ag(I), which was further amplified by the medium as per the equation = + [OH]. Interestingly, the ionic strength remained unchanged throughout the reaction, exerting no discernible effect on the reaction rate.

View Article and Find Full Text PDF

Want AI Summaries of new PubMed Abstracts delivered to your In-box?

Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!