The Journal of Physical Chemistry B最新文献

{"title":"Skin Hydration by Natural Moisturizing Factors, a Story of H-Bond Networking.","authors":"Marving Martin, Benjamin Chantemargue, Patrick Trouillas","doi":"10.1021/acs.jpcb.4c05473","DOIUrl":"10.1021/acs.jpcb.4c05473","url":null,"abstract":"<p><p>Dry skin is a common condition that is experienced by many. Besides being particularly present during the cold season, various diseases exist all year round, leading to localized xerosis. To prevent it, the skin is provided with natural moisturizing factors (NMFs). They are small amino acids or derivatives found in the outermost layer of the skin, the <i>stratum corneum</i> (SC). They are often claimed to be highly efficient humectants, increasing the water content to maintain the fluidity of the skin. However, alternative mechanisms have been proposed, suggesting that NMFs themselves may act as lipid mobility amplifiers. This work aims at investigating the role of three NMFs, namely, urea (URE), glycerol (GLY), and urocanic acid/urocanate (UCA/UCO) in SC in silico models, considering two different levels of humidity. Molecular dynamic simulations showed an increase in the diffusion of different lipid components, mainly free fatty acids (FFAs) and ceramide acyl chain moieties, in the presence of either high water content or NMFs. The membrane properties were modified, as seen by an increased thickness and greater lateral stiffness. All NMFs exhibited a similar impact, whereas UCA revealed slight differences according to its charged state. By studying NMF-water intermolecular interactions, we highlighted the role of NMF as a regulator of membrane perturbations while ensuring membrane fluidity. This role allows NMFs to prevent destabilization of the skin membrane in the presence of high water content. This study, performed at an atomistic resolution, highlighted a strong H-bond network between lipids involving mainly ceramides but also all other components. This network can be modified in the presence of a high water concentration or NMFs, resulting in modifications of membrane properties, rationalizing hydration effects.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":"844-852"},"PeriodicalIF":2.8,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142941791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of Divalent Cations on Polarity and Hydration at the Lipid/Water Interface Probed by 4-Aminophthalimide-Based Dyes.","authors":"Parvez Alam, Pramod Kumar, Harsh Sahu, Deepika Sardana, Pronab Kundu, Ajay Kumar Chand, Sobhan Sen","doi":"10.1021/acs.jpcb.4c05404","DOIUrl":"10.1021/acs.jpcb.4c05404","url":null,"abstract":"<p><p>The ion binding to the lipid/water interface can substantially influence the structural, functional, and dynamic properties of the cell membrane. Despite extensive research on ion-lipid interactions, the specific effects of ion binding on the polarity and hydration at the lipid/water interface remain poorly understood. This study explores the influence of three biologically relevant divalent cations─Mg²⁺, Ca²⁺, and Zn²⁺─on the depth-dependent interfacial polarity and hydration of zwitterionic DPPC lipid in its gel phase at room temperature. To measure these depth-dependent properties, we use a series of solvatochromic fluorescent probes synthesized based on 4-aminophthalimide with varying alkyl chain lengths (4AP-Cn; <i>n</i> = 5, 7, and 9). Employing steady-state fluorescence experiments and all-atom molecular dynamics (MD) simulations, we quantify changes in interfacial polarity and hydration induced by the cations binding to the lipid/water interface. Our results reveal that Zn²⁺ induces a significant blue shift in the fluorescence spectra of all 4AP-Cn dyes, indicating a marked decrease in local polarity (<i>E</i>_T^N ≤ 0.05) at the lipid/water interface compared to Mg²⁺ and Ca²⁺, which results in a higher polarity (<i>E</i>_T^N ≥ 0.2). The depth-dependent fluorescence spectra of dyes at the interface in the presence of Mg²⁺ and Ca²⁺ remain similar to those in the absence of cations, with only a minor red shift observed for Mg²⁺, implying a slight hydration effect. MD simulations show that cations primarily bind to the headgroup and glycerol regions of lipid. Simulations also reveal that Zn²⁺ causes substantial dehydration at the lipid/water interface, as detected by the 4AP-Cn dyes, while Mg²⁺ and Ca²⁺ have less pronounced effects, with only slight hydration induced by Mg²⁺. This study highlights the distinct positional effects of cations probed by 4AP-Cn probes at the lipid-water interface, underscoring the potential of 4AP-Cn dyes for monitoring depth-dependent changes in membrane properties induced by external agents or environmental conditions.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":"930-941"},"PeriodicalIF":2.8,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142941589","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Manifestation of Rouse and Entanglement Dynamics in Non-Cross-Linked and Cross-Linked Polymers Studied by Field-Cycling and Multiple Quantum NMR.","authors":"M Becher, F M Salamanca, J L Valentin, K Saalwächter, E A Rössler","doi":"10.1021/acs.jpcb.4c05547","DOIUrl":"10.1021/acs.jpcb.4c05547","url":null,"abstract":"<p><p>Rubbers prepared from technical poly(butadiene) and natural poly(isoprene) are studied by field-cycling (FC) ¹H NMR relaxometry to elucidate the changes of the relaxation spectrum. Starting with the non-cross-linked polymer successively cross-links are introduced via sulfur or peroxide vulcanization. Applying an advanced home-built relaxometer allows one to probe entanglement dynamics in addition to Rouse dynamics. We show that entanglement dynamics evidenced in terms of a characteristic power-law in the NMR susceptibility is still observed with an exponent identical to that in non-cross-linked linear polymers. Yet, the entanglement regime disappears more and more from the accessible frequency window upon increasing the cross-link density and a spectrally enlarged Rouse regime is revealed. Adding a swelling agent, the manifestation of the Rouse and entanglement regimes virtually does not change, yet, the apparent power-law exponents increase. Concomitant multiple-quantum (MQ) ¹H NMR experiments provide information on the structure of the rubber network in terms of the residual dipolar coupling and the fraction of the network defects, i.e., persisting entangled or nonentangled chains, introduced upon cross-linking and swelling.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":"1082-1094"},"PeriodicalIF":2.8,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142941687","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Molecular Dynamics Simulation Study on Heterogeneous Structure, Rheology, and Dynamic Correlation of Concentrated Aqueous Solutions of a Lithium Salt.","authors":"Tsuyoshi Yamaguchi","doi":"10.1021/acs.jpcb.4c07942","DOIUrl":"10.1021/acs.jpcb.4c07942","url":null,"abstract":"<p><p>Molecular dynamics simulation of an aqueous solution of lithium bis(trifluoromethanesulfonyl)amide, LiTFSA, was performed at various concentrations to relate its liquid structure with frequency-dependent shear viscosity. The structure factor exhibited a low-<i>q</i> peak that represents a heterogeneous structure composed of water and anion domains, and the lithium ion existed in the water domain due to its strong hydration. The frequency-dependent shear viscosity showed bimodal relaxation, and the relative contribution of the slower mode increased with an increase in the salt concentration. The cross-correlation between the shear stress and the two-body density revealed that the slower viscoelastic mode is assigned to the dynamics of the heterogeneous structure, and the assignment was also confirmed by the comparison between the viscoelastic and structural relaxations. The collective translational motions of the cation and the anion showed a strong negative correlation in a concentrated solution, reflecting the heterogeneous domain structure.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":"1026-1035"},"PeriodicalIF":2.8,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142941702","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Confinement-Induced Self-Assembly of Protein Nanofibrils Probed by Microfocus X-ray Scattering.","authors":"Saeed Davoodi, Eirini Ornithopoulou, Calvin J Gavillet, Anton Davydok, Stephan V Roth, Christofer Lendel, Fredrik Lundell","doi":"10.1021/acs.jpcb.4c04386","DOIUrl":"10.1021/acs.jpcb.4c04386","url":null,"abstract":"<p><p>We here explore confinement-induced assembly of whey protein nanofibrils (PNFs) into microscale fibers using microfocused synchrotron X-ray scattering. Solvent evaporation aligns the PNFs into anisotropic fibers, and the process is followed in situ by scattering experiments within a droplet of PNF dispersion. We find an optimal temperature at which the order parameter of the protein fiber is maximized, suggesting that the degree of order results from a balance between the time scales of the forced alignment and the rotational diffusion of the fibrils. Furthermore, the assembly process is shown to depend on the nanoscale morphology and flexibility of the PNFs. Stiff/straight PNFs with long persistence lengths (∼2 μm) align at the air-water interface, with anisotropy decreasing toward the center of the droplet as Marangoni flows increase entanglement toward the center. By contrast, flexible/curved PNFs with shorter persistence lengths (<100 nm) align more uniformly throughout the droplet, likely due to enhanced local entanglements. Straight PNFs pack tightly, forming smaller clusters with short intercluster distances, while curved PNFs form intricate, adaptable networks with larger characteristic distances and more varied structures.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":"1070-1081"},"PeriodicalIF":2.8,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11770757/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142976772","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"DFT-Based Polarizable Ion Models for Molten Rare-Earth Chlorides: From Lanthanum to Europium.","authors":"Kateryna Goloviznina, Maria-Chiara Notarangelo, Julien Tranchida, Emeric Bourasseau, Mathieu Salanne","doi":"10.1021/acs.jpcb.4c07931","DOIUrl":"10.1021/acs.jpcb.4c07931","url":null,"abstract":"<p><p>We developed a systematic polarizable force field for molten trivalent rare-earth chlorides, from lanthanum to europium, based on first-principle calculations. The proposed model was employed to investigate the local structure and physicochemical properties of pure molten salts and their mixtures with sodium chloride. We computed densities, heat capacities, surface tensions, viscosities, and diffusion coefficients and disclosed their evolution along the lanthanide series, filling the gaps for poorly studied elements, such as promethium and europium. The analysis of the local arrangement of chloride anions around lanthanide cations revealed broad coordination number distributions with a typical [from 6 to 9]-fold environment, the maximum of which shifts toward lower values with the increase of atomic number as well as upon dilution of the salt in sodium chloride. The neighboring lanthanide chloride complexes were found to be connected by sharing a corner or an edge of the corresponding polyhedra.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":"1016-1025"},"PeriodicalIF":2.8,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142941584","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Probing Macromolecular Conformation in Restricted Geometry by PEF: Application to Hydrophobically Modified PAMAM Dendrimers Isolated Inside Surfactant Micelles.","authors":"Donghan Liu, Sanjay Patel, Yuting Xie, Hanbo Zhang, Jean Duhamel","doi":"10.1021/acs.jpcb.4c07737","DOIUrl":"10.1021/acs.jpcb.4c07737","url":null,"abstract":"<p><p>The conformation of a series of zero-generation polyamidoamine dendrimers end-labeled with four 1-pyrene-butyroyl, -hexanoyl, -octanoyl, -decanoyl, and -dodecanoyl derivatives, referred to as the PyCX-PAMAM-G0 samples with <i>X</i> = 4, 6, 8, 10, and 12, respectively, was characterized in <i>N</i>,<i>N</i>-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and aqueous solutions of 50 mM sodium dodecyl sulfate (SDS) or 50 mM dodecyltrimethylammonium bromide (DTAB). The conformation of the PyCX-PAMAM-G0 samples was determined from the global model-free analysis (MFA) of the fluorescence decays, which yielded the average rate constant (⟨<i>k</i>⟩) for pyrene excimer formation (PEF) between an excited and a ground-state pyrenyl labels, with ⟨<i>k</i>⟩ being proportional to the local concentration ([Py]_loc) of the pyrenyl labels within the macromolecular volume; ⟨<i>k</i>⟩-vs-[Py]_loc plots yielded straight lines passing through the origin in DMF and DMSO, demonstrating that the internal segments of the dendrimers obeyed Gaussian statistics in these two solvents. In aqueous surfactant solutions, the hydrophobic pyrenyl labels induced the interactions of the PyCX-PAMAM-G0 dendrimers with the SDS and DTAB micelles. Plots of ⟨<i>k</i>⟩ as a function of [Py]_loc yielded straight lines passing through the origin for the PyCX-PAMAM-G0 samples with <i>X</i> equal to 4, 6, and 8, indicating that the internal segments of these three dendrimers obeyed Gaussian statistics within the surfactant micelles. However, ⟨<i>k</i>⟩ departed from the straight lines for the PyCX-PAMAM-G0 samples with <i>X</i> = 10 and 12 associated with the SDS and DTAB micelles. This behavior indicated that [Py]_loc was much larger than expected for the dendrimers prepared with longer alkanoyl linkers. This behavior was attributed to strong hydrophobic interactions between the longer linkers and the dodecyl tails of the surfactants in the hydrophobic core of the micelles, which induced a conformational change for the dendrimers inside the micelles, that could be probed at the molecular level by PEF.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":"1144-1153"},"PeriodicalIF":2.8,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142941784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Temperature Dependence of Intermolecular Dynamics and Liquid Properties of Deep Eutectic Solvent, Reline.","authors":"Hideaki Shirota, Maharoof Koyakkat, Juriti Rajbangshi, Ranjit Biswas","doi":"10.1021/acs.jpcb.4c06838","DOIUrl":"10.1021/acs.jpcb.4c06838","url":null,"abstract":"<p><p>We investigated the temperature dependence of the intermolecular dynamics, including intermolecular vibrations and collective orientational relaxation, of one of the most typical deep eutectic solvents, reline, using femtosecond Raman-induced Kerr effect spectroscopy (fs-RIKES), subpicosecond optical Kerr effect spectroscopy (ps-OKES), and molecular dynamics (MD) simulations. According to fs-RIKES results, the temperature-dependent intermolecular vibrational band peak at ∼90 cm^-1 exhibited a redshift with increasing temperature. The density-of-state (DOS) spectrum of reline by MD simulations reproduced this fs-RIKES spectral feature. The decomposition analysis of the DOS spectra showed that all constituent components, including urea, cholinium cation, and chloride anion, also exhibited similar magnitudes of redshifts upon heating, indicating that the three species intermolecularly interact one another. The temperature sensitivity of the intermolecular vibrational frequency was high compared to that of ionic liquids. According to ps-OKES results, the slow orientational relaxation rate increased with increasing temperature; however, this phenomenon was not well explained by the Stokes-Einstein-Debye hydrodynamic model. Analysis of the orientational relaxation time based on the Stokes-Einstein-Debye model indicates that the decoupling between the orientational relaxation time and viscosity occurs at temperatures below ∼330 K. Quantum chemistry calculations of urea and the cholinium cation based on the MP2/6-311++G(d,p) level of theory confirmed that the contribution of intramolecular vibrational bands to low-frequency bands below 200 cm^-1 was minimal. The densities, viscosities, electrical conductivities, and surface tensions of reline at various temperatures were also estimated and compared with the dynamics data.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":"965-978"},"PeriodicalIF":2.8,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142968762","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hindered Sedimentation of Tungsten Carbide Particles in a Hydroxyl-Terminated Polybutadiene-Based Polymer-Bonded Explosive Energetic Composite System.","authors":"Kaixiang Yang, Jinying Wang, Jie Dong, Kang Niu, Zhineng Wang, Jiaxin Lu, Yuan Tian Jing, Lixin Mu, Zixuan Su","doi":"10.1021/acs.jpcb.4c08328","DOIUrl":"10.1021/acs.jpcb.4c08328","url":null,"abstract":"<p><p>Energetic composite systems with uniform particle distributions are of considerable interest, but sedimentation is a persisting challenge. Tungsten carbide (WC, density: 15.36 g/cm³) particles are promising cemented carbide particles owing to their desirable properties. In this study, we investigated the mitigation of sedimentation in a polymer-bonded explosive (PBX) energetic composite by optimizing the viscosity and particle distribution using WC particles and a hydroxyl-terminated polybutadiene-based binder. A simulation based on a modified version of Stokes' law is used to study the sedimentation behaviors of the system at different viscosities, and the resistance coefficient of particle sedimentation is estimated. The PBX energetic composite system loaded with the WC particles is prepared and analyzed. In the early curing stages, when the resistance coefficient is 0.65-1.95 (×10⁹), the sedimentation rate is low, but increases rapidly as the viscosity of the system increases. When the effective viscosity is ≥11,510 MPa·s, the particle sedimentation is improved. The energetic components are tightly entangled within the binder, with no exposure or agglomeration, and the WC particles are evenly distributed. The system can reach a solid content of 91% and retain its pourability. Thus, an energetic composite system loaded with high-density metal particles is prepared, providing a reference for use in PBX formulation.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":"1154-1165"},"PeriodicalIF":2.8,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142976777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Free Energy, Rates, and Mechanism of Transmembrane Dimerization in Lipid Bilayers from Dynamically Unbiased Molecular Dynamics Simulations.","authors":"Emil Jackel, Gianmarco Lazzeri, Roberto Covino","doi":"10.1021/acs.jpcb.4c05242","DOIUrl":"https://doi.org/10.1021/acs.jpcb.4c05242","url":null,"abstract":"<p><p>The assembly of proteins in membranes plays a key role in many crucial cellular pathways. Despite their importance, characterizing transmembrane assembly remains challenging for experiments and simulations. Equilibrium molecular dynamics simulations do not cover the time scales required to sample the typical transmembrane assembly. Hence, most studies rely on enhanced sampling schemes that steer the dynamics of transmembrane proteins along a collective variable that should encode all slow degrees of freedom. However, given the complexity of the condensed-phase lipid environment, this is far from trivial, with the consequence that free energy profiles of dimerization can be poorly converged. Here, we introduce an alternative approach, which relies only on simulating short, dynamically unbiased paths, avoiding using collective variables or biasing forces. By merging all paths, we obtain free energy profiles, rates, and mechanisms of transmembrane dimerization with the same set of simulations. We showcase our algorithm by sampling the spontaneous association and dissociation of a transmembrane protein in a lipid bilayer, the popular coarse-grained Martini force field. Our algorithm represents a promising way to investigate assembly processes in biologically relevant membranes, overcoming some of the challenges of conventional methods.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143027483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}