The Journal of Physical Chemistry B最新文献

Graphene has emerged as a promising candidate for adsorption and separation applications due to its exceptional properties. In this study, the diffusion properties and local structure of the CO₂-NO flue gas, CH₄, and H₂O mixtures in the free state and those confined within graphene layers were investigated via molecular dynamics simulation. Additionally, density functional theory calculation was performed to determine the adsorption energies of these four components at different adsorption sites on graphene. The results showed that the graphene structure significantly altered the diffusion coefficients of the four substances, with the order becoming CH₄ > NO > CO₂ ≫ H₂O. By contrast, in the absence of graphene at low temperatures, the diffusion coefficient order was H₂O > CO₂ > NO > CH₄. Simultaneously, the temperature and pressure exerted pronounced regulatory effects on CH₄, CO₂, and NO. Analysis of the relative diffusion coefficients of CH₄ and NO revealed that the optimal conditions for the adsorption and separation of this mixture with bilayer graphene structures were 1-10 MPa and 275 K.

Huntingtin exon-1 (HTTex1) aggregation at cellular membranes contributes to the propagation of toxic protein assemblies in Huntington's disease. We explore the thermodynamic and structural mechanisms linking membrane binding, curvature sensing, and nucleation of the aggregates. Here, we use the OpenAWSEM coarse-grained force field code with an effective membrane potential to quantify the folding and surface aggregation behavior of three HTTex1 constructs on both flat lipid bilayers and spherical vesicles. The computed free energy profiles reveal a strong α-helical NT₁₇-mediated affinity (ΔG_bind = -9 kcal/mol) and a curvature-dependent enhancement of this binding, with effective enrichments of protein concentration at the membrane surface of approximately 1000-fold for the NT₁₇ by itself, compared to 18-fold for the polyQ-extended constructs NT₁₇-polyQ and 36-fold for NT₁₇-polyQ-polyP. The free-energy aggregation landscapes demonstrate that membrane proximity also enhances the formation of larger oligomers and promotes early oligomerization through N-terminal anchoring. Analyzing curvature-sensation analyses across vesicle radii shows deeper insertion on highly curved surfaces along with stronger binders, consistent with experimental vesicle-binding assays. Our results establish a mechanistic framework for understanding how membranes can act as two-dimensional platforms that both concentrate HTTex1 and template the formation of aggregation nuclei.

Highly polar solvents are generally considered to significantly quench the luminous emission of rare-earth doping luminescence materials. In this work, we reported a counterintuitive luminescence phenomenon in Dy/Eu@Gd-MOFs. Their photoluminescence (PL) behaviors in propanol/butanol isomers exhibit trends of emission intensity that inversely correlate with solvent polarity. This phenomenon should not be simplistically ascribed to quenching induced solely by reabsorption, solvent effects, or high-frequency vibrational groups. The structural differences among propanol and butanol isomers result in diversified high-frequency and fingerprint-region vibrational modes. When these vibrations resonate with the critical energy gap, they nonradiative decay in the sensitizer through vibrational coupling, thereby steering energy toward the activator. Time-resolved spectra acquired at different temperatures provide a detailed analysis and evidence for this opinion. These findings give an unconventional interpretation for solvent-induced luminescence quenching in rare-earth luminescence materials, enabling a novel route for modulating their excited states through solvent engineering.

Lipid membrane phase separation, which is a thermodynamic physical process, has attracted attention as a dynamic function of cellular interfaces. As membrane tension influences the phase separation of cellular membranes under isothermal conditions, it is essential to clarify the physicochemical mechanism involved. Living cells contain numerous macromolecules that can generate osmotic pressure across the membrane due to the semipermeable nature of the lipid bilayer. In this research, we examined how macromolecular surroundings and the transmembrane osmotic pressure influence membrane phase separation, utilizing model membranes like giant lipid vesicles. We generated osmotic pressure across the membrane using dextran (molecular weights 40,000 and 200,000) and polyethylene glycol (molecular weight 6,000) as model macromolecules. Microscopic observations represented the changes in the percentage of phase-separated vesicles and miscibility temperature caused by osmotic tension, indicating that macromolecular surroundings tend to suppress membrane phase separation, while macromolecular osmotic pressure across the membrane markedly induces phase separation. Lipid membrane phase separation can be regulated by the macromolecular concentration and osmotic pressure across the membrane. This finding offers new insights into the formation and regulation of membrane domains within the macromolecularly crowded environments of living cells.

In this study, we have investigated the concentration-dependent intermolecular dynamics of aqueous solutions of aniline hydrochloride, sodium phenoxide, and 4-methylpyridine using femtosecond Raman-induced Kerr effect spectroscopy at 298 K. The densities, viscosities, and surface tensions of the aqueous solutions were also measured at 298 K. Quantum chemistry calculations of the target aromatics and their clusters with water molecule(s) or a counterion were performed to obtain their optimized structures and cluster interaction energies. In the difference low-frequency Kerr spectra (<250 cm^-1) of the aqueous aromatic solutions and neat water, the first moment (M₁) of the intermolecular vibrational band, which mainly originated from the aromatic ring, showed that the librations of the anilinium cation and phenoxide anion were higher in frequency than that of 4-methylpydine. Furthermore, the libration of the phenoxide anion was also higher in frequency than that of the anilinium cation. Quantum chemistry calculations indicated that the strong hydrogen bonding and compact hydration structure resulting from the negatively charged aromatic ring led to higher-frequency libration of the phenoxide anion than the anilinium cation. In addition, the M₁ increased with increasing concentration. The concentration sensitivities were stronger in aqueous solutions of aniline hydrochloride and sodium phenoxide than in aqueous solutions of 4-methylpyridine. Based on the quantum chemistry calculation results, we conclude that strong aromatic-water and aromatic-counterion interactions lead to a higher-frequency libration of aromatics with charged side groups. The collective orientational relaxation times of the aqueous aromatic solutions showed the fractional Stokes-Einstein-Debye behavior.

The α7-nicotinic acetylcholine receptor (α7-nAChR) is a cation-selective Cys-loop receptor involved in diverse physiological processes and is an important therapeutic target. Multiple cryo-EM structures of putative open states are now available, and their functional relevance is under active investigation. Here, we combined single-channel patch-clamp recordings with atomistic molecular dynamics (MD) simulations to assess the conductive properties of several α7-nAChR structures solved with different ligands. Simulations restrained to the respective cryo-EM structures produced only modest ion flux for all models, inconsistent with experiment, whereas fully unrestrained simulations revealed marked differences in their ability to relax into physiologically conductive ensembles. Two structures, 7KOX and ligand-bound 8V82, consistently stabilized into conductive states whose permeation properties agreed with our measured inward single-channel conductance. The conduction of 8V82 nearly stopped upon removing the ligands resolved in the PDB structures. 8V80 showed only intermittent conduction with ligands, and remained nonconductive without them. 7EKT collapsed into a nonconductive conformation upon relaxation, irrespective of whether the modeled ligands were retained or removed. 9LH5, despite having a transmembrane pore nearly identical to 7KOX's, exhibited approximately 2-fold higher conductance, likely due to a widened extracellular vestibule. Across models, permeation events followed Poissonian statistics with a characteristic entry lag captured by a double-Poisson model. Simulations of outward currents consistently overestimated the conductance compared to experiments, perhaps reflecting the absence of the full intracellular domain in available structural models and/or the presence of current-blocking concentrations of cytosolic Mg²⁺ in patch-clamp cell-attached recordings. These results identify the conformations most compatible with the physiological open state and underscore the importance of unrestrained MD, ligand stabilization, and extracellular-vestibule geometry in shaping α7-nAChR conduction.

Triplet photosensitizers are essential in photocatalytic hydrogen production and photoredox organic transformations, relying on efficient light absorption, intersystem crossing, and subsequent electron or energy transfer processes. Recent developments have focused on transition metal complexes with favorable electronic configurations, such as Cu(I) complexes, which feature extended excited-state lifetimes and reduced nonradiative decay. In contrast, Zn(II) complexes, despite being isoelectronic with Cu(I), are generally dismissed as photosensitizers because they predominantly exhibit ligand-centered emission, and MLCT states, when observed, are short-lived and poorly suited for photocatalysis. Nonetheless, their tunable coordination chemistry, low toxicity, and catalytic potential make them promising candidates. In this work, we demonstrate that Zn(II) complexes can be deliberately engineered to act as efficient triplet photosensitizers by exploiting intraligand charge transfer (ILCT) rather than MLCT. We report a comparative study of Zn(II) complexes supported by redox-noninnocent tridentate pincer ligands bearing different aryl substituents, revealing pronounced differences in triplet-state behavior. Structural analysis shows that coplanarity between the aryl-azo and phenanthroline moieties is essential for efficient ILCT and long-lived triplet emission. To elucidate the role of the metal center, a structurally analogous Cd(II) complex was examined, which exhibits photophysical behavior nearly identical to its Zn(II) counterpart, confirming that the metal primarily enforces ligand geometry rather than participating electronically in the excited state. Both Zn(II) and Cd(II) complexes function as effective photosensitizers for singlet-oxygen-mediated oxidation, achieving photocatalytic efficiencies of approximately 50%. Although this efficiency is lower than that of certain Ir-based systems, this work establishes a design strategy in which unfavorable metal-centered electronic interactions are intentionally bypassed, and the metal serves chiefly as a structural anchor. These findings position Zn(II) complexes as sustainable, earth-abundant photosensitizers and provide a new framework for designing triplet photosensitizers based on closed-shell metal ions.

Ether-based electrolytes have gained increasing attention for energy storage based on their utility as solvate ionic liquids at high concentration and their role in forming effective cointercalation complexes at graphite electrodes. While transferrable atomistic models have been proposed to describe glyme ether solutions at varying concentration and backbone chain lengths, coarse-grained models have not been extensively explored. The need for coarse-grained descriptions is emphasized by the formation of potentially mesoscale aggregate structures which enable efficient ion transport. Herein we describe a simple approach to developing such models using a combination of a charge smearing for long-ranged electrostatics and Boltzmann Inversion to develop short-ranged tabulated potentials. The impact of long-ranged interactions on electrolyte structure and the ingredients to the coarse-grained models are discussed along with the importance of system selection for training the short-ranged portion. Overall, the final model shows good transferability for diglyme and monoglyme, which share an emphasis on ion association, but fails to capture the solvent separated ionic structure of triglyme electrolytes.

Post-translational modifications (PTMs) such as phosphorylation, acetylation, and methylation critically expand proteome function by regulating protein structure and interactions. Hydropathy changes serve as a main driving force; however, a quantitative, mechanistic understanding of how their distinct chemical changes alter local protein hydropathy remains limited. To bridge this gap, we extend the Protocol for Assigning a Residue's Character on a Hydropathy (PARCH) scale, a residue-level hydropathy scale, to systematically evaluate PTM-induced physicochemical changes. By applying this method, we quantify the effect and magnitude of hydropathy shifts at modification sites and map how these perturbations influence the local protein environment. Our analysis reveals that phosphorylation exerts a strong, consistent hydrophilic effect, significantly increasing PARCH values due to the introduction of a large, charged phosphate group. In contrast, N-lysine acetylation, which neutralizes charge, shows context-dependent effects, predominantly increasing the hydrophobicity but occasionally enhancing the local hydrophilicity. Methylation presents the most complex signature, with no uniform trend, where increased side chain bulk can paradoxically increase water exposure despite the modification's nonpolar nature. This study establishes the PARCH scale as a powerful quantitative tool for deciphering how PTMs regulate the local hydropathy landscape of proteins, providing a predictive foundation for understanding their structural, hydropathy, and functional consequences.

We introduce a novel series of excited state intramolecular proton transfer (ESIPT)-active 2-phenylbenzimidazole fluorophores (1-3) as highly selective turn-on probes for insulin amyloid aggregates (IAAs). Synthesized via an eco-friendly, metal-free route, these probes show high specificity for IAAs over native insulin and Thioflavin-T (ThT). Density functional theory (DFT) calculations confirm the intrinsic ESIPT mechanism, while photophysical studies reveal that a specific binding mode restricts molecular motion, enhancing quantum yield and fluorescence lifetime. Crucially, the lead compound (3) binds to a unique site distinct from ThT, as proven by competitive binding and Förster Resonance Energy Transfer (FRET) assays. It also exhibits superior affinity, a low detection limit, the ability to modulate aggregation kinetics, and excellent biocompatibility. This work moves beyond ThT, positioning the ESIPT-active 2-phenylbenzimidazole scaffold as a promising theranostic tool for amyloid-related pathologies such as Type-2 diabetes.