We study thermodynamic responsive properties of a grafted polyanion layer on a planar surface by using statistical density-functional theory. The structure and electrostatics of the grafted layer are explored by varying the strength (ε) of dispersion interaction (DPI) and salt concentration (ρ salt ). The brush behaviors are determined by the competition and interplay between the DPI and the screening effect of small ions (counterions and salt ions). The DPI has a positive contribution to brush swelling, while the doping salt has either a positive or negative contribution depending on the concentration. At low surface grafting density (ρ g ), the DPI plays a prominent role at low ρ salt ; the screening effect dominates the behavior only at high ρ salt . At high ρ g , the screening effect is always important because the counterion density inside the brush is high; the electrostatic interaction is weak in most cases so that the brush layer is sensitive to the DPI. Both structure and electrostatics of the grafted layer can be regulated and controlled by varying ε and ρ salt . These results provide useful predictions and a fundamental understanding for the thermodynamic properties in a polyelectrolyte-grafted surface.
Polymer electrode materials are critical components to achieve the excellent energy storage performance (ESP) of supercapacitors, while the underlying microscopic mechanism by which the polymer structure on the electrode surface affects the energy storage remains unclear. Herein, we explore the effects of a polyelectrolyte (PE) coating on the ESP of supercapacitors by using the polymer density functional theory. The ESP is determined by the adsorption of free ions at the electrode surface, which is jointly affected by the interactions from both the charged surface and the anchored PE chains. Once the PE chains carry like charges as the electrode, the energy density can be significantly promoted by two orders of magnitude. However, if the PE chains carry opposite charges to the electrode, the energy density can be suppressed. The effect of PE coating on the capacitance is similar to that on the energy density if the surface voltage is fixed during the operation, and otherwise, if the surface charge density is fixed, the effect on the capacitance is opposite to that on the energy density. This work provides a microscopic understanding of the complex polyelectrolyte coating’s effects on the ESP in supercapacitors.
Weakly (or partially) charged polyelectrolytes represent an important subset of the polyelectrolyte family. For instance, polycarboxylate-based superplasticizers, or PCEs, are comb-shaped polyelectrolytes possessing anionic backbones grafted with neutral side chains. PCEs play an important role in modern concrete production. However, their behavior in salt solutions remain poorly understood. The present work builds upon a recently developed liquid-state theory for fully charged polyelectrolyte solutions and extends it to describe the phase behavior and salt partitioning of PCEs in a 2:1 salt solution. Previous studies have shown that there can be an additional short-range attraction, often referred to as the "calcium-binding" interaction between calcium ions and the negatively-charged carboxylate groups of PCEs. Such a calcium-binding interaction and how its strength affects the phase behavior are investigated. It is found that increasing the calcium-binding strength expands the phase-separated region and increases the critical extra salt concentration, and it also leads to a wider phase-separated region for salting-out and salting-in phenomena. The structural parameters of PCEs also affect the phase behavior. Increasing the side-chain length shrinks the phase-separated region, while increasing the acid-to-ether ratio expands the phase-separated region. Those results may find applications in molecular design of weakly charged polyelectrolytes like PCEs.
The proto-oncogene protein RET is a receptor tyrosine kinase that plays an important role in the development and progress of various human cancers. Currently, targeting RET with small-molecule tyrosine kinase inhibitors (TKIs) has been established as promising therapeutic strategy for thyroid carcinoma (TC). However, two gatekeeper mutations V804M and V804L in RET kinase domain have been frequently observed to cause drug resistance during the targeted therapy, largely limiting the application of reversible TKIs in TC. Here, we described an integrative protocol that combined literature curation, computational analysis, and in vitro kinase assay to systematically investigate the response profile of 9 approved RET TKIs to the two clinical RET gatekeeper mutations. It was revealed that the two mutations exhibit a similar energetic behavior to influence TKI binding, which can moderately decrease competitive inhibitor affinity and modestly increase substrate ATP affinity simultaneously. However, the binding potency of few second-generation kinase inhibitors such as Ponatinib and Alectinib can be improved to overcome the increased ATP affinity, thus restoring their inhibitory activity against the kinase mutants. Subsequently, the established protocol was employed to investigate the response profile of 4 commercially available RET TKIs that are under preclinical or clinical development. Three out of the four TKIs were found to become resistant upon the mutations due to steric hindrance effect introduced by the mutated residues, while the remaining one was moderately sensitized by the mutations since the mutated residues can form additional hydrophobic and van der Waals interactions with the inhibitor.
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