Separating monovalent anions of similar size and charge, such as acetate (Ac⁻) and chloride (Cl⁻), remains highly challenging in membrane processes. Using molecular dynamics simulations, we explored functionalized graphene surfaces with tunable fractions of protonated amine (-NH₃⁺) and deprotonated carboxyl (-COO⁻) groups (ratios 0:10 to 10:0) in a NaAc/NaCl mixed solution. We identified a charge-regulated selectivity reversal process: -COO⁻-rich, negatively charged surfaces showed only a weak Cl⁻ preference (α_Cl⁻_/Ac⁻ = 1.06–2.71), whereas -NH₃⁺-dominated, positively charged surfaces achieved strong Ac⁻ selectivity, up to 14.86, for an 8:2 -NH₃⁺:-COO⁻ ratio. Decomposing permeability into solubility and diffusivity showed that the Ac⁻ advantage on -NH₃⁺-rich surfaces was more than 80 % diffusion-dominated, whereas the small Cl⁻ preference on -COO⁻ surfaces reflected slight, counterbalancing changes in solubility and diffusivity. Interfacial hydration analysis linked the selectivity to the dehydration difference between Ac⁻ and Cl⁻. The maximum Ac⁻/Cl⁻ selectivity coincided with the largest ΔN_Ac⁻_-Cl⁻ between the bulk and the interface. Together, our work reveals interfacial dehydration-controlled diffusion as the main mechanism for separating Ac⁻ from Cl⁻ on charge-regulated graphene surfaces and offers a quantitative design rule recommending setting the -NH₃⁺:-COO⁻ ratio near 8:2 to optimize membrane functionalization for challenging monovalent anion separations.

The synthesis of biodegradable polymers with high temperature sensitivity based on natural materials to replace the notorious non-biodegradable poly(NIPAAm) remains a highly challenging task. It requires an optimal balance between hydrophilic groups, ensuring aqueous solubility, and hydrophobic groups that facilitate thermal response. In particular close to the human body temperature. We synthesized biodegradable pullulan microspheres with temperature sensitivity, comparable to poly(NIPAAm) microgels, by first succinylating pullulan to introduce carboxylic groups, then partially amidating these groups with isopropylamine. Preliminary Molecular Dynamics simulations guided the determination of suitable substitution levels necessary for achieving desired thermosensitivity. The resulting microgels exhibit rapid swelling/deswelling kinetics (in a scale of seconds), with a remarkable collapse to nearly the original dry volume. Importantly, their transition temperature can be finely adjusted through progressive ionization of residual carboxyl groups. Enzymatic biodegradation studies indicated a slow degradation rate.

The spike protein encoded by the SARS-CoV-2 has become one of the most studied macromolecules in recent years due to its central role in COVID-19 pathogenesis. The spike protein’s receptor-binding domain (RBD) directly interacts with the host-encoded receptor protein, ACE2. This review critically examines computational insights into RBD’s interaction with ACE2 and with therapeutic antibodies designed to interfere with this interaction. We begin by summarizing insights from early computational studies on pre-pandemic SARS-CoV-1 RBD interactions and how these early studies shaped the understanding of SARS-CoV-2. Next, we highlight key theoretical contributions that revealed the molecular mechanisms behind the binding affinity of SARS-CoV-2 RBD against ACE2, and the structural changes that have enhanced the infectivity of emerging variants. Special attention is given to the “RBD charge rule”, a predictive framework for determining variant infectivity based on the electrostatic properties of the RBD. Towards applying the computational insights to therapy, we discuss a multiscale computational protocol for optimizing monoclonal antibodies to improve binding affinity across multiple spike protein variants, including representatives from the Omicron family. Finally, we explore how these insights can inform the development of future vaccines and therapeutic interventions for combating future coronavirus diseases.

Deep eutectic solvents (DESs) have recently gained attention due to their tailorable properties and versatile applications in several fields, including green chemistry, pharmaceuticals, and energy storage. Their tunable properties can be enhanced by mixing DESs with cosolvents such as ethanol, acetonitrile, and water. DESs are structurally complex, and molecular modeling techniques, including quantum mechanical calculations and molecular dynamics simulations, play a crucial role in understanding their intricate behavior when mixed with cosolvents. While the most studied cosolvent is water, in some applications, even a small content of water is considered a contaminant, for example, when the processes of interest require dry conditions. Only quite recently have modeling studies begun to focus on DES mixed with cosolvents other than water. This tutorial provides the first comprehensive overview of these studies. It highlights how modern molecular modeling increases our understanding of their structural organization, transport properties, phase behavior, and thermodynamic properties. Additionally, case studies and recent developments in the field are discussed along with the challenges and future directions in molecular modeling of DES in cosolvent mixtures. Overall, this review offers valuable insights into the molecular-level understanding of DES-cosolvent systems and their implications for designing novel solvent mixtures with tailored properties for various applications.

In liquid lubrication, the stability of the lubricating film and friction coefficient is governed by the liquid type and contact conditions. However, altering the friction coefficient of the liquid on some specific surface under constant conditions (such as speed, pressure. etc) is challenging. In this work, we developed a non-contact and reversibly switchable approach to control the nano friction of phosphonium-based ionic liquid (ILs) [P_4,4,4,8][BOB] on titanium oxide (TiO₂) surfaces via ultraviolet light. The co-ion effect promotes anion adsorption, generating an ordered interfacial structure and a novel sliding interface that favors the formation of elastic hydrodynamic or mixed lubrication regimes, thereby reducing friction by over 60 % compared to the initial dark-state condition and achieving superlubricity (friction coefficient μ < 0.01) under high contact pressure (24 MPa) on sub-nanometer rough TiO₂ surfaces. The study demonstrates under photo-induced activation, TiO₂ reacts with adsorbed water molecules to form a hydroxyl network and undergo protonation reactions, resulting in a positive surface charge. Combined simulation and force curve measurements, it is revealed that this condition will lead to an orderly and stable arrangement of ILs within near-surface layers. These findings offer valuable insights for the design of light-responsive lubricants and their integration into MEMS/NEMS.

The aim of the present study was to dissect the nature of intermolecular interactions leading to the improved solubility of glibenclamide in an aqueous solution of the choline tryptophanate, [Cho][Trp], ionic liquid. To this end, experimental ¹H and ¹³C NMR measurements and computational modeling employing classical molecular dynamics (MD) simulations and combined quantum mechanics/molecular mechanics (QM/MM) models were carried out. Samples of glibenclamide dissolved in water and in an aqueous mixture of [Cho][Trp] were scrutinized both experimentally and computationally. MD simulations revealed that the constituent ions of the ionic liquid condensed around the drug molecule pushing water molecules away. Nevertheless, virtually no specific hydrogen bonding interactions between glibenclamide and the ions were formed. The hydrotropic activity of the [Cho][Trp] ionic liquid thus occurs through the formation of dynamic aggregates between the solute and the ions, which screen the hydrophobic glibenclamide from polar water molecules. Experimental ¹H NMR measurements have shown that the largest changes in chemical shifts were registered for protons in the benzene rings of glibenclamide, implying that these are the main sites of interaction with the ions of the ionic liquid – a conclusion well-corroborated by the results of MD simulations. The good qualitative agreement between the computational QM/MM-based and experimental NMR spectra of glibenclamide in an aqueous solution and in aqueous mixture of [Cho][Trp] provides support to the structural results.

Alignment effects caused by a heat flow in the cholesteric liquid crystal phase of three coarse grained molecular model systems based on the Gay–Berne potential have been studied by molecular dynamics simulation. In order to keep the systems homogeneous, the Evans heat flow algorithm, where a fictitious mechanical heat field rather than a temperature gradient drives the heat flow, was used. It was found that the cholesteric axis orients in such a way that the heat flow and thereby the irreversible energy dissipation rate are minimized. This is in accordance with a theorem stating that the irreversible energy dissipation rate is minimal in the linear regime of a nonequilibrium steady state. In two of the studied systems this means that the cholesteric axis orients parallel to the heat field and the heat flow. Then the heat field induces a torque that rotates the director around the cholesteric axes which is the basis of the Lehmann effect. However, in one of the systems, the cholesteric axis orients perpendicularly to the heat field and a torque is exerted that rotates the cholesteric axis around the heat field. This is a transport phenomenon that has not been studied before.

Density-functional theory (DFT) has become an extensively and successfully used tool in the studies of molecules and materials. However, DFT remains computationally expensive, especially for exploring the conformational space of molecular systems comprising a few hundred atoms. Here, we present a Reduced Approach to Density-functional Expansion (RADE), devised to substantially reduce the computational cost of standard DFT methods. RADE can be implemented fully non-empirically as an efficient first-principles electronic structure method. Preliminary results for molecules containing elements H, C, N, and O indicate that this method can, in general, reproduce well the results from standard DFT calculations.

In this study, new pyrrolo[3',4':3,4]pyrrolo[1,2-a][1,10]phenanthroline derivatives are developed and their stabilities and transformation pathways are investigated. The synthetic approach toward these novel derivatives include a pivotal [3 + 2] cycloaddition of in situ generated ylides, followed by cycloadducts oxidation and other unexpected transformations. The structures of the intermediate and final compounds are proposed based on information obtained from several spectral techniques. Stability study reveal that electron-donating groups in the para position of the phenyl ring promote easier oxidation, whereas electron-withdrawing substituents enhance the stability of the compounds. The acid–base titration of α-monosubstituted 1,10-phenanthroline 6a results in a reversible color change, which is preliminarily explored through spectral methods.

Raman spectroscopy can provide highly sensitive and detailed information about the structural fingerprint of molecules, enabling their identification. In this study, our aim is to understand the enhanced intensity observed in experimental Raman measurements. Five azobenzene derivatives were selected, each substituted with different functional groups, for both experimental and theoretical investigations. To reproduce the experimental trend, we employed various levels of theory using the QM-DFT approach. Theoretical results were compared to experimental data through both qualitative and quantitative analyses. A good correlation between theoretical and experimental results was achieved when considering electronic transitions to predict the theoretical Raman spectra and interpret the experimental data. Our theoretical results indicate that even dark (nπ*) transitions, which are forbidden and have an oscillator strength close to zero, can have a signature in the Raman spectra due to the resonance effect with incident energy. Additionally, the vibrational modes stimulated by the presence of ππ* bright states, being at the pre-resonance with the incident energy, was clearly separated from the vibrational frequencies of the dark states, which was evinced in the Raman fingerprint. Theoretical Raman spectra of azobenzene derivatives, substituted with push–pull moieties, revealed contributions from the charge transfer transitions (nπ*CT, ππ*CT) as well as back-donation of electron density, observed for the first time in an azobenzene derivative. Our protocol, proposing a quantitative and qualitative overlap between theoretical and experimental data, confirms the presence of combination modes between vibrational levels and electronically excited states.