The Journal of Physical Chemistry B最新文献

{"title":"Diffusion of Submicron Particles on Biological Surfactant Monolayers Governed by the Viscoelasticity and Interfacial Dynamics.","authors":"Yang Liu, Xu Zheng, Weiguo Liang, Feng Gao, Yinghao Wang","doi":"10.1021/acs.jpcb.5c04851","DOIUrl":"https://doi.org/10.1021/acs.jpcb.5c04851","url":null,"abstract":"<p><p>The diffusion of microscale and nanoscale particles on biological membranes plays a critical role in understanding various physiologic processes and optimizing drug delivery. In this study, we investigate the diffusive motion of submicron particles on in vitro porcine pulmonary surfactant monolayers at the air-water interface using single-particle tracking. The viscoelastic response of the monolayer becomes apparent only when particle sizes fall below the Saffman and Delbrück length. Hydrodynamic and nonhydrodynamic interfacial dynamics induce distinct anomalous diffusion behaviors for small and large particles, respectively. For smaller particles, their thermal velocities approach the minimum phase velocity of interfacial capillary waves, causing a hydrodynamic wave drag, whose magnitude can be approximately modeled using the sudden accelerated/decelerated rectilinear motion of an object at the interface. In contrast, larger particles do not exhibit wave drag due to their lower thermal velocities. Instead, their displacement correlation functions reveal unusually slow-decaying oscillations─a phenomenon fundamentally stemmed from nanoscale contact-line interfacial dynamics. These oscillations are linked to the diffusion coefficient that varies instantaneously with the particle's immersion depth. By performing Langevin dynamics simulations of the particle's perpendicular motion, we confirmed that the oscillation period precisely coincides with the cyclic time of the particle's motion along the interfacial normal direction. These simulations explicitly account for subtle contact-line perturbations to the interfacial free energy, which arise from nanoscale surface heterogeneity of the particle. This behavior demonstrates strong dynamic coupling between in-plane and out-of-plane particle motions. Crucially, the oscillation amplitude becomes magnified when the particle's transverse displacement per unit time decreases, explaining why these oscillations are exclusively observable in larger particles. The displacement probability distributions (DPDs) remain non-Gaussian even at long elapsed times when the diffusion becomes linear. This non-Gaussianity stems from variations in the diffusion coefficients of individual particles, which originate from the heterogeneity of the monolayer's structure.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145205208","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":"Vibrational Spectroscopic Analysis of Water Absorption in Polyimides and the Correlation with Dielectric Properties at 10 GHz.","authors":"Ririka Sawada, Haonan Liu, Shinji Ando","doi":"10.1021/acs.jpcb.5c05709","DOIUrl":"https://doi.org/10.1021/acs.jpcb.5c05709","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Unveiling the mechanism behind the relative humidity (RH) dependence of the dielectric properties of polyimides (PIs) in the high-frequency (GHz) range is a crucial challenge in the development of novel low-dielectric thermally stable polymers. Herein, the correlations among the dielectric constant (&lt;i&gt;D&lt;/i&gt;&lt;sub&gt;k&lt;/sub&gt;), dissipation factor (&lt;i&gt;D&lt;/i&gt;&lt;sub&gt;f&lt;/sub&gt;), water absorption content, and hydrogen-bonding structures of sorbed H&lt;sub&gt;2&lt;/sub&gt;O molecules were precisely analyzed for 15 types of aromatic and semiaromatic PIs based on variable-RH Fourier transform infrared (FT-IR) vibrational spectroscopy. The absorbance of the IR bands assignable to the O-H stretching (ν(OH)) and H-O-H bending (δ(HOH)) vibrations of H&lt;sub&gt;2&lt;/sub&gt;O molecules sorbed in PI films gradually increased with an increase in the RH of the atmosphere. Notably, the slopes of the increase in &lt;i&gt;D&lt;/i&gt;&lt;sub&gt;k&lt;/sub&gt; and &lt;i&gt;D&lt;/i&gt;&lt;sub&gt;f&lt;/sub&gt; against the integrated area of the δ(HOH) IR band (&lt;i&gt;A&lt;/i&gt;&lt;sub&gt;δ(HOH)&lt;/sub&gt;), which can be used as a measure of the concentration of sorbed H&lt;sub&gt;2&lt;/sub&gt;O, were nearly constant and independent of the chemical structure of PIs. However, the slopes of the RH dependences of &lt;i&gt;D&lt;/i&gt;&lt;sub&gt;k&lt;/sub&gt; and &lt;i&gt;D&lt;/i&gt;&lt;sub&gt;f&lt;/sub&gt;, that is, &lt;i&gt;h&lt;/i&gt;&lt;sub&gt;Dk&lt;/sub&gt; and &lt;i&gt;h&lt;/i&gt;&lt;sub&gt;Df&lt;/sub&gt;, were strongly dependent on the structure of PIs and proportional to each other. This confirms that the amount of water absorbed is a crucial factor in the RH dependence of &lt;i&gt;D&lt;/i&gt;&lt;sub&gt;k&lt;/sub&gt; and &lt;i&gt;D&lt;/i&gt;&lt;sub&gt;f&lt;/sub&gt;. The &lt;i&gt;D&lt;/i&gt;&lt;sub&gt;k&lt;/sub&gt; values of the PIs increased linearly with an increase in &lt;i&gt;A&lt;/i&gt;&lt;sub&gt;δ(HOH)&lt;/sub&gt;, whereas the &lt;i&gt;D&lt;/i&gt;&lt;sub&gt;f&lt;/sub&gt; values increased linearly with &lt;i&gt;A&lt;/i&gt;&lt;sub&gt;δ(HOH)&lt;/sub&gt; at a lower RH but gradually showed a concave-up increase at a higher RH. In addition, the relationship between &lt;i&gt;A&lt;/i&gt;&lt;sub&gt;δ(HOH)&lt;/sub&gt; and &lt;i&gt;D&lt;/i&gt;&lt;sub&gt;f&lt;/sub&gt; for all PIs was nearly aligned along a single master curve. This unified and marked increase in &lt;i&gt;D&lt;/i&gt;&lt;sub&gt;f&lt;/sub&gt; could be induced by both the large &lt;i&gt;D&lt;/i&gt;&lt;sub&gt;f&lt;/sub&gt; of water (∼0.5) and the plasticization effect of the H&lt;sub&gt;2&lt;/sub&gt;O molecules sorbed in the PI films. This water-induced plasticization activates the local relaxation motions of the moieties with large dipole moments, i.e., the imide and ester groups, in the PI chains, resonating at 10 GHz. Furthermore, the spectral decomposition of the IR ν(OH) band enables the classification and characterization of the structures of sorbed and hydrogen bonded H&lt;sub&gt;2&lt;/sub&gt;O molecules at the molecular level, namely 1) H&lt;sub&gt;2&lt;/sub&gt;O molecules directly form hydrogen bonds (HBs) with imide carbonyl (C═O) groups, called \"bound water,\" and 2) H&lt;sub&gt;2&lt;/sub&gt;O molecules form HBs with bound water, called \"self-associated water.\" Notably, with an increase in &lt;i&gt;A&lt;/i&gt;&lt;sub&gt;δ(HOH)&lt;/sub&gt;, the total amount of the spectral components of self-associated water (&lt;i&gt;A&lt;/i&gt;&lt;sub&gt;assoc&lt;/sub&gt;) increased curvilinearly and simultaneously with &lt;i&gt;D&lt;/i&gt;&lt;sub&gt;f&lt;/sub&gt;. The qu","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145205211","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":"Tunable Conformational Properties of POSS-Peptide Conjugate Molecule in Selective Solvents: An Atomistic Molecular Dynamics Simulation Study.","authors":"Junhao Dai, Wen Tang, Xianbo Huang, Rui Zhang","doi":"10.1021/acs.jpcb.5c05243","DOIUrl":"https://doi.org/10.1021/acs.jpcb.5c05243","url":null,"abstract":"<p><p>Giant molecules with precisely defined modular architectures hold promise to generate distinct structure-dynamics-property relationships in solution-phase materials. Recently, a novel class of hybrid macromolecules that combine structural rigidity of polyhedral oligomeric silsesquioxanes (POSS) with flexibility of peptide sequences (POSS-peptide conjugate molecules) have been established experimentally. To elucidate their detailed microscopic structural and dynamic features, high-precision atomistic modeling and simulation are in demand. In this study, we develop a standardized and extensible all-atom force field parametrization workflow for POSS-peptide molecules, integrating quantum chemical calculations to derive accurate force field parameters for the rigid POSS units, including bond, angle, and dihedral terms, as well as atomic charges for the whole molecule. Upon applying the parametrization framework to five representative POSS-peptide molecules with varied POSS functionality and peptide composition in water or DMF solvent, all-atom molecular dynamics simulations are performed for the ten systems to investigate the highly tunable conformational properties of POSS-peptides. We construct detailed conformational free energy landscapes that provide insight into the role of different factors in shaping the molecule's solution-phase behavior. Our analysis reveals that molecular structure and solvent polarity co-regulate the conformational preferences of POSS-peptide molecules. Of particular interest is the finding of some unusual structure-dynamics correlation behaviors driven by close-distance interactions between the POSS and peptide unit. This work expands our understanding of the conformational richness of POSS-peptides in solution and provides a methodology foundation for exploring larger-scale supramolecular structures achievable by this emergent family of giant molecules in future research.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145205193","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":"Correlation between σ-Profile Characteristics and Infinite Dilution Activity Coefficients of Choline Chloride-Urea DES: Experimental Determination and Machine Learning Interpretation.","authors":"Xinpeng Bi, Dezhi Cao, Xinyue Wang, Dingkai Hu, Qiang Wang","doi":"10.1021/acs.jpcb.5c04547","DOIUrl":"https://doi.org/10.1021/acs.jpcb.5c04547","url":null,"abstract":"<p><p>This study integrates inverse gas chromatography (IGC) experiments with machine learning (ML) to systematically investigate the thermodynamic properties of choline chloride (ChCl)-urea (1:2) deep eutectic solvent (DES) and its interaction mechanisms with organic solvents. IGC measurements determined the infinite dilution activity coefficients (γ₁₂^∞) and related thermodynamic parameters for 46 representative organic solvents within the temperature range of 303.15-343.15 K. Results revealed the hierarchy of solute-DES interaction strength: hydrocarbons (increasing with chain length) > alkenes > ethers > aromatics > ketones > esters > alcohols (weakest due to hydrogen bonding). To enhance γ₁₂^∞ prediction accuracy, a novel approach fused the quantized σ-profile partitioning descriptors of the DES with temperature as input features, constructing four ML models. Compared to the significant deviation of the COSMO-SAC model prediction (<i>R</i>² = 0.8224), the Extreme Gradient Boosting (XGBoost) model demonstrated superior performance (test set <i>R</i>² = 0.9979, average absolute relative deviation (AARD) < 20%). Feature importance analysis indicated that σ-profile regions corresponding to weak hydrogen bond acceptor (HBAs) character [S3: -0.0084 ≤ σ ≤ 0 e/Ų] and weak hydrogen bond donor character [S4, 0 ≤ σ ≤ 0.0084 e/Ų] contributed dominantly (42%) to the γ₁₂^∞ prediction. In contrast, the strongly polar region [S5, 0.0084 ≤ σ ≤ 0.02 e/Ų] reduced γ₁₂^∞ by enhancing interactions, confirming the \"like dissolves like\" principle. This framework enables high-precision γ₁₂^∞ prediction solely from molecular structures (Applicability Domain (AD) covers 93.85% of data), providing an efficient and reliable theoretical tool for DES-based green solvent design and optimization of industrial separation processes, such as benzene/methanol systems.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145197421","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":"How Surface Functionalization Controls Confined Electrolyte Structure and Dynamics at Graphene Interfaces.","authors":"Lyndon T M Hess, Nhi P T Nguyen, Anthony H Dee, Anant K Gupta, Zachary Kwon, Shuwen Yue","doi":"10.1021/acs.jpcb.5c04964","DOIUrl":"https://doi.org/10.1021/acs.jpcb.5c04964","url":null,"abstract":"<p><p>Understanding how surface chemistry modulates confined electrolyte behavior is critical for advancing electrochemical, membrane, and nanofluidic technologies. Here, we present a comprehensive molecular dynamics study of aqueous NaCl solutions confined between graphene functionalized with -COOH, -OH, ═O, and -CH₃ groups across multiple surface coverages and electrolyte concentrations. We systematically disentangle how functional group identity and abundance independently shape interfacial layering, ion adsorption, and water dynamics. Polar, hydrogen-bonding groups (-COOH, -OH) strongly structure the interface and suppress water mobility, while weakly polar (═O) and nonpolar groups (-CH₃) lead to more diffuse, mobile profiles. Importantly, we show that functional group chemistry sets the morphology of interfacial structure, while coverage scales its intensity, a distinction that holds across electrolyte concentrations. These findings enable a quantitative framework for designing chemically heterogeneous surfaces that precisely modulate ion and solvent behavior in complex electrolyte environments.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145197442","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":"Role of Hydration in Excited-State Proton Transfer in Adenine-Thymine Nucleobase Pairs.","authors":"Moumita Banerjee, Nilanjan Mitra","doi":"10.1021/acs.jpcb.5c03607","DOIUrl":"https://doi.org/10.1021/acs.jpcb.5c03607","url":null,"abstract":"<p><p>This study investigates the excited-state proton transfer (ESPT) mechanism in canonical adenine-thymine (A-T) nucleobase pairs under gas-phase and explicitly hydrated conditions. Using a combination of time-dependent density functional theory (TDDFT), static potential energy surface (PES) analyses, and nonadiabatic surface hopping dynamics, we reveal that hydration induces a mechanistic switch from charge-transfer-driven ESPT in the gas phase to solvent-assisted proton relay in aqueous environments. Explicit hydration environment modulates both the energetic landscape and the nature of electronic transitions, reducing charge-transfer character and stabilizing proton-transferred intermediates. Difference density plots and UV-vis spectra highlight excited-state antiaromaticity as a potential driving force for ESPT, which is further supported by computed aromaticity indices. Dynamical simulations demonstrate that excitation to higher singlet states (S₂) enhances access to proton transfer channels, particularly in hydrated systems. Overall, our results offer a unified mechanistic framework for understanding how hydration, excited-state reactivity, and photophysical stability are intricately linked in DNA base pairs, advancing insight into photoprotection and mutation pathways under biologically relevant conditions.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145205164","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":"Disaggregation at High Volume Exclusion: An \"Overcrowding\" Effect.","authors":"Leon Koch, Dominik Baier, Satyendra Rajput, Benedikt König, Michael Tiemann, Simon Ebbinghaus, Divya Nayar, Klaus Huber","doi":"10.1021/acs.jpcb.5c01245","DOIUrl":"https://doi.org/10.1021/acs.jpcb.5c01245","url":null,"abstract":"<p><p>Macromolecular crowding has an impact on any process in liquids of living systems like the cytoplasm or blood caused by the high solid contents in these liquids. Although interactions might occur in as many facets as there are components in the solid content, the impact of macromolecules, like proteins, RNA, and DNA, establishes a considerable part of the solids, which is likely dominated by volume exclusion. However, cells are not homogeneously crowded, and local spots with exceptional crowding density and volume exclusion, like it is the case in some biomolecular condensates, exist. Here, we study the effect of such conditions on self-assembly processes using two distinct types of highly water-soluble macromolecular crowders (Ficoll and silica nanoparticles) and pseudo isocyanine chloride (PIC) acting as probe species. PIC exhibits fibrillar aggregates in analogy to many self-assembling proteins, while forming hierarchical structures in fulfilling specific tasks. The sharp <i>J</i>-band in UV-vis spectroscopy of the fibrillar PIC aggregates allows for precise detection of its self-assembly in complex systems. As expected, both crowders promote the process of self-assembly by depletion interactions. However, we observed a reversal of this effect due to topological constraints at crowder concentrations high enough to reach the overlap or space filling concentration. The work is complemented by molecular dynamics simulations and a preliminary study of the self-assembly of fibrinogen, a key player in blood clotting, in the presence of Ficoll, thereby validating what has been observed with PIC as a synthetic probe. Experiments and simulations suggest that at highest crowding conditions, the effects on biomolecular self-assembly may be reversed compared to what is excepted from previous studies in the field, leading to the phenomenon that we term \"overcrowding\".</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145197416","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":"Nanoconfinement and Interface Effects on Calcium Phosphate Aggregation within a 2D Nanochannel: Insights from Deep-Learning Molecular Dynamics.","authors":"Tian Xia, Rui-Tian Ma, Jia-Ying Li, Hui Liu, Hai-Bo Yi","doi":"10.1021/acs.jpcb.5c04375","DOIUrl":"https://doi.org/10.1021/acs.jpcb.5c04375","url":null,"abstract":"<p><p>In this study, we investigated the hydration and aggregation dynamics of Ca²⁺ and phosphate species, as well as the structural characteristics of calcium phosphate clusters, within a two-dimensional (2D) nanochannel using molecular dynamics simulations with a deep learning potential. Our findings show that ion dynamics are markedly enhanced under confinement, primarily due to accelerated water dynamics. Ion hydration within the 2D nanochannel is reduced as a result of layered water distribution and frequent water exchange around ions compared to the bulk phase solution, thereby facilitating coordination between Ca²⁺ and phosphate species despite observed polarization effects. However, an increased energy barrier for association between Ca²⁺ and phosphate species can slow their aggregation within the 2D nanochannel. Since protonated phosphate species exhibit a stronger preference for interfacial water layers than PO₄^3-, fewer protons are present in cluster of Ca²⁺ and phosphate species in the bulk-like region, which facilitates the association of Ca²⁺ and phosphate species. The interfacial enrichment of protonated species can also promote the transformation of amorphous calcium phosphate (ACP) to hydroxyapatite. Our results presented here elucidate the influence of nanoconfinement and interfacial interactions on calcium phosphate aggregation within 2D nanochannels, offering valuable insights into biological and biomimetic mineralization processes.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145197419","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":"QM/MM Studies on Photoinduced Cycloaddition and (6-4) Reactions of the Thymidine:4-Selenothymidine Dimer in Aqueous Solution.","authors":"Rui Zhao, Jia-Ling Dai, Bin-Bin Xie, Bo-Wen Yin, Li Shuai","doi":"10.1021/acs.jpcb.5c06035","DOIUrl":"https://doi.org/10.1021/acs.jpcb.5c06035","url":null,"abstract":"<p><p>Selenonucleobases have garnered increasing interest from both experimental and theoretical communities for their promising roles in photodynamic therapy and DNA cross-linking. Similar to the extensively investigated thymidine:4-thiothymidine system, the selenium-modified thymidine:4-selenothymidine (Tp^4SeT) dimer may also exhibit significant photochemical activity within DNA duplexes. However, its detailed photochemical reaction mechanisms remain largely unexplored. Herein, we employed high-level MS-QM(CASPT2//CASSCF) method to explore excited-state decay, [2 + 2] cycloaddition and (6-4) reactions of Tp^4SeT in aqueous solution. Our calculations revealed five possible nonadiabatic decay channels enabling population of the T₁ state from the initial S₂ state, mediated by two multistate intersections of S₂/S₁/T₂/T₁ and S₁/T₂/T₁. Following population of the T₁ state, the [2 + 2] cycloaddition proceeds via a stepwise, nonadiabatic mechanism. That is, the pathway starts from Tp^4SeT in the T₁ state via the T_1CC or T_1CSe intermediates and ultimately ends up with Se⁵-selenetane in the S₀ state. Subsequent transformation of Se⁵-selenetane into the Se⁵-(6-4) product occurs through a concerted reaction in the ground state, characterized by the simultaneous cleavage of the C₄-Se₈ bond and formation of the S₈-H₉ bond. This study provides detailed mechanistic insights into the photoreactivity of selenonucleobases in DNA duplexes at the molecular level.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145190438","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":"α-Tocopherol and a Polyunsaturated Phospholipid Prefer Each Other's Company in Mixed Membranes with Raft-Forming Sphingomyelin and Cholesterol: MD Simulations.","authors":"Samuel W Canner, Patrick Kelley, Alexander Q Phillips, Scott E Feller, Stephen R Wassall","doi":"10.1021/acs.jpcb.5c05553","DOIUrl":"https://doi.org/10.1021/acs.jpcb.5c05553","url":null,"abstract":"<p><p>α-Tocopherol (αtoc), the biologically active form of vitamin E, protects membrane lipids from oxidative damage. Previous hypotheses suggest that αtoc preferentially associates with polyunsaturated phospholipids to optimize protection of the lipid species most susceptible to oxidation, but this idea is challenged by recent work showing lower affinity for polyunsaturated than monounsaturated phospholipids. With coarse-grained and all-atom MD simulations, in this study we explore the lateral distribution of αtoc in bilayers composed of mixtures of <i>N</i>-palmitoyl sphingomyelin (PSM), cholesterol, and 1-palmitoyl-2-docosaheaxaenoylphosphatidylcholine (PDPC) that separate into ordered raft-like domains enriched in saturated PSM and cholesterol, surrounded by disordered nonraft regions enriched in polyunsaturated PDPC. Analyses assigning lipids to raft-like and nonraft environments reveal that αtoc is largely excluded from PSM-rich/cholesterol-rich raft-like domains and preferentially accumulates with PDPC in nonraft regions. We suggest that the high concentration of cholesterol in lipid rafts drives αtoc into nonraft regions, facilitating its role as an antioxidant.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145197430","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}