The Journal of Physical Chemistry B最新文献

{"title":"Revealing the Role of Electronic Effect to Modulate the Photophysics and Z-Scan Responses of <i>o</i>-Locked GFP Chromophores.","authors":"Debasish Paul, Priyadarshi Sahoo, Arunava Sengupta, Umakanta Tripathy, Soumit Chatterjee","doi":"10.1021/acs.jpcb.4c04104","DOIUrl":"10.1021/acs.jpcb.4c04104","url":null,"abstract":"<p><p>Three novel core green fluorescent protein (GFP) chromophore analogues, based on a doubly locked conformation and variable electronic effects by replacing one hydrogen with bromine, iodine, and methyl, respectively, have been synthesized to modulate the push-pull effect. These chromophores exhibited intramolecular H-bonding, as evidenced by single-crystal X-ray and ¹H NMR studies. The fluorescence quantum yields (ϕ_f) of all of the chromophores were found to be more than an order of magnitude higher (∼0.2) than the unlocked chromophores (∼0.01). It was found that the electronic effect did affect the nonradiative rates, as the quantum yields were found to vary with respect to different analogues in the same solvents. The effect of the push-pull effect was also evident by a higher Stokes-shifted emission in the case of the methyl derivative with respect to the bromo- and iodo-analogues. Furthermore, the emission spectra of these GFP chromophores were found to show positive solvatochromism, which was supported by a quantum chemical calculation. A detailed study, correlating the observed spectral changes with various solvent functions and supported by computational results, established a facile proton transfer, followed by twisted intramolecular charge transfer (TICT) to be the major nonradiative channels of these chromophores. Besides, a completely novel usage of these chromophores was explored for the first time by studying their third-order nonlinear optical characteristics in DMSO using a single-beam Z-scan technique. All of the chromophores exhibited tunable nonlinear refraction (NLR) and nonlinear absorption (NLA) properties that depend upon different substituent groups present in the chromophores. Here, the NLR was due to the effect of self-defocusing, whereas the NLA was triggered by reverse saturable absorption, which is attributed to the two-photon absorption (TPA) process. Surprisingly, the efficiency of the TPA ability of the chromophores was found to be a function of the induced electronic effect. Hence, this work opens a new route for the utility of the <i>ortho</i>-locked GFP chromophores in the field of nonlinear optical applications.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":"692-711"},"PeriodicalIF":2.8,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142542926","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":"Generating Ultradense Jammed Ellipse Packings Using Biased SWAP.","authors":"Robert S Hoy","doi":"10.1021/acs.jpcb.4c06533","DOIUrl":"10.1021/acs.jpcb.4c06533","url":null,"abstract":"<p><p>Using a Lubachevsky-Stillinger-like growth algorithm combined with biased SWAP Monte Carlo and transient degrees of freedom, we generate ultradense disordered jammed ellipse packings. For all aspect ratios α, these packings exhibit significantly smaller intermediate-wavelength density fluctuations and greater local nematic order than their less-dense counterparts. The densest packings are disordered despite having packing fractions ϕ_J(α) that are within less than 0.5% of that of the monodisperse-ellipse crystal [ϕ_xtal = π/(2√3) ≃ 0.9069] over the range 1.2 ≲ α ≲ 1.45 and coordination numbers <i>Z</i>_J(α) that are within less than 0.5% of isostaticity [<i>Z</i>_iso = 6] over the range 1.2 ≲ α ≲ 2.6. Lower-α packings are strongly fractionated and consist of polycrystals of intermediate-size particles, with the largest and smallest particles isolated at the grain boundaries. Higher-α packings are also fractionated, but in a qualitatively different fashion; they are composed─of increasingly large locally nematic domains─reminiscent of liquid glasses.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":"763-770"},"PeriodicalIF":2.8,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142908827","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":"Halogenated Cholesterol Alters the Phase Behavior of Ternary Lipid Membranes.","authors":"Deeksha Mehta, Elizabeth K Crumley, Jinchao Lou, Boris Dzikovski, Michael D Best, M Neal Waxham, Frederick A Heberle","doi":"10.1021/acs.jpcb.4c06318","DOIUrl":"10.1021/acs.jpcb.4c06318","url":null,"abstract":"<p><p>Eukaryotic plasma membranes exhibit nanoscale lateral lipid heterogeneity, a feature that is thought to be central to their function. Studying these heterogeneities is challenging since few biophysical methods are capable of detecting domains at submicron length scales. We recently showed that cryogenic electron microscopy (cryo-EM) can directly image nanoscale liquid-liquid phase separation in extruded liposomes due to its ability to resolve the intrinsic thickness and electron density differences of ordered and disordered phases. However, the intensity contrast between these phases is poor compared with conventional fluorescence microscopy and is thus both a limiting factor and a focal point for optimization. Because the fundamental source of intensity contrast is the spatial variation in electron density within the bilayer, lipid modifications aimed at selectively increasing the electron density of one phase might enhance the ability to resolve coexisting phases. To this end, we investigated model membrane mixtures of DPPC/DOPC/cholesterol in which one hydrogen of cholesterol's C19 methyl group was replaced by an electron-rich halogen atom (either bromine or iodine). We characterized the phase behavior as a function of composition and temperature using fluorescence microscopy, Förster resonance energy transfer, and cryo-EM. Our data suggest that halogenated cholesterol variants distribute approximately evenly between liquid-ordered and liquid-disordered phases and are thus ineffective at enhancing the intensity difference between them. Furthermore, replacing more than half of the native cholesterol with halogenated cholesterol variants dramatically reduces the size of the membrane domains. Our results reinforce how small changes in the sterol structure can have a large impact on the lateral organization of membrane lipids.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":"671-683"},"PeriodicalIF":2.8,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142941575","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":"Technique for Creating 3D Ordered Colloidal Crystals with Hexagonal Close Packing and Uniform Thickness over a Large Area.","authors":"Alina Fumina, Anastasiya Speshilova, Ilya Belyanov, Ekaterina Endiiarova, Artem Osipov","doi":"10.1021/acs.jpcb.4c06234","DOIUrl":"10.1021/acs.jpcb.4c06234","url":null,"abstract":"<p><p>Traditional approaches to creating colloidal crystals do not simultaneously achieve uniform thickness, three-dimensional ordering, and large areas of defect-free hexagonal close-packed domains. Only the realization of all these conditions will allow the use of colloidal crystals as templates for fabricating inverse opals with a tunable photonic band gap. Therefore, we propose a novel approach for creating 3D colloidal crystals. It combines the use of the Langmuir-Blodgett (LB) process to form the first layer and sequential spin-coating processes to form all following layers. The original automated LB trough, equipped with a feedback control system for surface pressure control, allowed the formation of a close-packed monolayer across the entire area of a 76 mm substrate, obtaining a defect-free domain area of 3000 μm². As a result of the developed spin-coating technique, bilayer and three-layer colloidal crystals based on polystyrene spheres (1.25 and 1.8 μm) were obtained. Three-dimensional HCP structure covered ≈96.5% of the substrate, and a defect-free domain area was obtained at least 1000 μm². The high degree of 3D ordering was confirmed by the presence of stop bands in the transmission spectra at wavelengths corresponding to Bragg diffraction from parallel planes and a 2D array of spherical particles.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":"750-762"},"PeriodicalIF":2.8,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142783385","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":"A Combined Approach to Extract Rotational Dynamics of Globular Proteins Undergoing Liquid-Liquid Phase Separation.","authors":"Dominik Gendreizig, Abhishek Kalarikkal, Simon L Holtbrügge, Saumyak Mukherjee, Laura Galazzo, Svetlana Kucher, Arnulf Rosspeintner, Lars V Schäfer, Enrica Bordignon","doi":"10.1021/acs.jpcb.4c06259","DOIUrl":"https://doi.org/10.1021/acs.jpcb.4c06259","url":null,"abstract":"<p><p>The formation of protein condensates (droplets) via liquid-liquid phase separation (LLPS) is a commonly observed phenomenon in vitro. Changing the environmental properties with cosolutes, molecular crowders, protein partners, temperature, pressure, etc. has been shown to favor or disfavor the formation of protein droplets by fine-tuning the water-water, water-protein, and protein-protein interactions. Therefore, these environmental properties and their spatiotemporal fine-tuning are likely to be important also in a cellular context at the existing protein expression levels. One of the key physicochemical properties of biomolecules impacted by molecular crowding is diffusion, which determines the viscoelastic behavior of the condensates. Here, we investigate the change in the rotational diffusion of γD-crystallin, undergoing LLPS in vitro in aqueous solutions in the absence and presence of cosolutes. We studied its rotational dynamics using molecular dynamics simulations (MD), electron paramagnetic resonance (EPR) spectroscopy, and fluorescence spectroscopy. MD simulations performed under dilute and crowded conditions show that the rotational diffusion of crystallin in water is retarded by 1 to 2 orders of magnitude in the condensed phase. To obtain the rotational dynamics in the dilute phase, we used fluorescence anisotropy and to extract the retardation factor in the condensed phase, we used spin-labeled γD-crystallin proteins as EPR viscosity nanoprobes. Aided by a viscosity nanoruler calibrated with solutions at increasing sucrose concentrations, we validated the rotational diffusion retardation predicted by MD simulations. This study underlines the predictive power of MD simulations and showcases the use of a sensitive EPR nanoprobe to extract the viscosity of biomolecular condensates.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142996303","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 and Deformation-Induced Changes in the Mechanical Properties of the Amorphous Regions of Semicrystalline Polypropylene.","authors":"Małgorzata Polinska, Marcin Kozanecki, Artur Rozanski","doi":"10.1021/acs.jpcb.4c07863","DOIUrl":"https://doi.org/10.1021/acs.jpcb.4c07863","url":null,"abstract":"<p><p>This work is focused on the impact of temperature and deformation on the mechanical properties, specifically the elastic modulus (<i>E</i>_a) of the amorphous regions in semicrystalline polymers, using polypropylene as a case study. It has been shown that increasing temperature results in an <i>E</i>_a decrease due to the enhanced mobility of polymer chains, triggered by the activation of α relaxation processes within the crystalline component. Consequently, rising temperature reduces the \"stiffening\" effect of the crystalline regions on the interlamellar layers. Temperature decrease close to the glass transition causes a significant increase in the <i>E</i>_a value, reaching nearly 70 MPa. Next, the effects of crystalline/amorphous component orientation and undisturbed crystallite length on <i>E</i>_a were examined in materials deformed using a channel die at various compression ratios. At low compression ratios, <i>E</i>_a decreases nearly 4-fold, primarily due to the fragmentation of lamellar crystals in the absence of, or with relatively low, orientation of the crystalline and amorphous components. Conversely, at higher compression ratios, with minimal crystal fragmentation, increased orientation of both crystalline and amorphous regions along the deformation direction (<i>E</i>_a measurement direction) leads to a substantial increase in <i>E</i>_a. Ultimately, the material with the highest used compression ratio exhibited an <i>E</i>_a value approximately 20% higher than that of the undeformed material.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142996345","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":"Key Chlorophyll <i>a</i> Molecules in the Uphill Energy Transfer from Chlorophyll <i>f</i> to P700 in Far-Red Light-Adapted Photosystem I.","authors":"Yuka Nakamura, Mikihito Okochi, Shigeru Itoh, Akihiro Kimura","doi":"10.1021/acs.jpcb.4c05007","DOIUrl":"10.1021/acs.jpcb.4c05007","url":null,"abstract":"<p><p>Multiple far-red light-adapted photosystem I (FR-PSI) reaction centers are recently found to work in oxygenic photosynthesis. They contain a small amount of a new type pigment chlorophyll <i>f</i> (Chl <i>f</i>) in addition to the major pigment chlorophyll <i>a</i> (Chl <i>a</i>). FR-PSI differs from the conventional PSIs in plants and cyanobacteria, which use only visible light absorbed by Chl <i>a</i>, although the mechanism of FR-PSI is not fully clear yet. We theoretically studied the light-harvesting mechanism of FR-PSI of <i>Fischerella thermalis</i> PCC 7521, in which a small amount of Chl <i>f</i> transfers the excitation energy of FR-light uphill to Chl <i>a</i>. We constructed two types of exciton models for FR-PSI using pigment arrangements based on the structural information. A model that assumes the same site energy value for all of the antenna Chl <i>a</i> molecules reproduced most of the experimentally obtained properties. The transient absorption spectra, excitation energy relaxation, and mean first passage time (MFPT) of the excitation energy transfer from Chls <i>f</i> and <i>a</i> to the special pair P700 (a pair of Chl <i>a</i>/Chl <i>a'</i>) were numerically calculated. The model, however, could not reproduce the low but distinct absorption intensity between the Chl <i>a</i>- and Chl <i>f</i>-bands and predicted a rather slow energy transfer from Chl <i>f</i> to P700. Advanced \"modified models\" further tested the effect of modification of the site energy values at individual antenna Chl <i>a</i> molecules. The optical properties and MFPTs of FR-PSI were calculated for each model with modified site energy values to evaluate the uphill light-harvesting process. The analysis showed that Chl <i>a</i>-1131 and -1222 play key roles in the light-harvesting process from Chl <i>f</i> molecules to P700, regardless of the excitation wavelength. The locations and site energy values of these Chl <i>a</i> molecules were found to be essential to reproduce the unique uphill energy transfer function of FR-PSI.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":"599-610"},"PeriodicalIF":2.8,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142918697","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":"Influence of CTAB Reverse Micellar Confinement on the Tetrahedral Structure of Liquid Water.","authors":"Anupama Sharma, Mywish Anand, Sudip Chakraborty","doi":"10.1021/acs.jpcb.4c04773","DOIUrl":"https://doi.org/10.1021/acs.jpcb.4c04773","url":null,"abstract":"<p><p>The effect of confinement on the tetrahedral ordering of liquid water plays a vital role in controlling their microscopic structure and dynamics as well as their spectroscopic properties. In this article, we have performed the classical molecular dynamics simulations of four different CTAB/water/chloroform reverse micelles with varied water content to study how the tetrahedral ordering of nanoscale water inside reverse micellar confinement influences the microscopic dynamics and the structural relaxation of water···water hydrogen bonds and its impact on the low-frequency intermolecular vibrational bands. We have noticed from the results obtained from simulated trajectories the lowering trends of tetrahedral ordering of water pools in reverse micellar confinements as we move from bulk to confined and strictly confined environments. We have observed that the order of confinements significantly altered the relaxation pattern of water···water hydrogen bonds present in the nanoscale water pool of reverse micelles. The recrossing related to hydrogen bond dynamics can effectively explain the relaxation pattern of <math><msubsup><mi>C</mi><mi>HB</mi><mi>WW</mi></msubsup><mrow><mo>(</mo><mi>t</mi><mo>)</mo></mrow></math> under confinement. The Br^-1···water hydrogen bond depicts a much slower relaxation compared to the water···water hydrogen bonds inside reverse micelles. We have also explored the correlation between the tetrahedral ordering of nanoscale water pools and the relaxation of water···water hydrogen bonds with the 50 cm^-1 band for water inside reverse micelles. The computations reported that compared to bulk water, the band appearing at 50 cm^-1 for O···O···O triplet bending is nonuniformly blue-shifted by 18-45 cm^-1 for the nanoscale water pool inside reverse micelles, and the intensity of the band drops from bulk to confined and strictly confined environments, which indicates the reduced tendency of such triplet formation. It is observed that a significant intensity variation at the 200 cm^-1 band correlates with the effect of confinement on the tetrahedral ordering of the water pool inside reverse micelles. So, our observations support the influence of strictly confined environments on the tetrahedral water structure to adopt the quasi-two-dimensional water network and experience restricted longitudinal translations. It is further noticed that the 500 cm^-1 librational band is also found to be blue-shifted by 71-112 cm^-1 for the water pool in reverse micelles, and the extent of the shift being more noticeable for strictly confined environments correlates excellently with the sluggish relaxation of water···water hydrogen bonds in such environments.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142996338","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":"Ion-Ion Association in Bulk Mixed Electrolytes Using Global and Local Electroneutrality Constraints.","authors":"Elizabeth A Ploetz, Nathan D Smyers, Paul E Smith","doi":"10.1021/acs.jpcb.4c07583","DOIUrl":"https://doi.org/10.1021/acs.jpcb.4c07583","url":null,"abstract":"<p><p>Ion atmospheres play a critical role in modulating the interactions between charged components in solutions. However, a detailed description of the nature of ion atmospheres remains elusive. Here, we use Kirkwood-Buff theory, an exact theory of solution mixtures, together with a series of local and bulk electroneutrality constraints to provide relationships between all the net ion-ion distributions in bulk electrolyte mixtures. The validity of the underlying relationships is then confirmed using classical explicit solvent molecular simulations of a range of electrolyte mixtures. Further analysis indicates the ion distributions can be separated into two contributions, one resulting in charge neutralization, for which each ion contributes in proportion to its ionic strength, and the other accounting for all the solution thermodynamics. The relationships hold for atomic and molecular ions of any size and valency regardless of ionic strength, temperature, or pressure, in any solvent system.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142996339","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":"Hydronium Ions Are Less Excluded from Hydrophobic Polymer-Water Interfaces than Hydroxide Ions.","authors":"Ryan L Myers, Aoi Taira, Chuanyu Yan, Seung-Yi Lee, Lauren K Welsh, Patrick R Ianiro, Tinglu Yang, Kenichiro Koga, Paul S Cremer","doi":"10.1021/acs.jpcb.4c05748","DOIUrl":"10.1021/acs.jpcb.4c05748","url":null,"abstract":"<p><p>The cloud point temperatures of aqueous poly(<i>N</i>-isopropylacrylamide) (PNIPAM) and poly(ethylene) oxide (PEO) solutions were measured from pH 1.0 to pH 13.0 at a constant ionic strength of 100 mM. This ionic strength was reached by mixing the appropriate concentration of NaCl with either HCl or NaOH. The phase transition temperature of both polymers was nearly constant between pH 2.0 and 12.0. However, the introduction of 100 mM HCl (pH 1.0) led to an increase in the cloud point temperature, although this value was still lower than the cloud point temperature in the absence of salt. By contrast, the introduction of 100 mM NaOH (pH 13.0) caused a decrease in the cloud point temperature, both relative to adding 100 mM NaCl and adding no salt. Nuclear magnetic resonance (NMR) studies of these systems were performed below the cloud point temperature, and the chemical shifts closely tracked the corresponding changes in the phase transition temperature. Specifically, the introduction of 100 mM HCl caused the ¹H chemical shift to move downfield for the CH resonances from both PNIPAM and PEO, while 100 mM NaOH caused the same resonances to move upfield. Virtually no change in the chemical shift was seen between pH 2.0 and 12.0. These results are consistent with the idea that a sufficient concentration of H₃O⁺ led to polymer swelling compared to Na⁺, while substituting Cl^- with OH^- reduced swelling. Finally, classical all-atom molecular dynamics (MD) simulations were performed with a monomer and 5-mer corresponding to PNIPAM. The results correlated closely with the thermodynamic and spectroscopic data. The simulation showed that H₃O⁺ ions more readily accumulated around the amide oxygen moiety on PNIPAM compared with Na⁺. On the other hand, OH^- was more excluded from the polymer surface than Cl^-. Taken together, the thermodynamic, spectroscopic, and MD simulation data revealed that H₃O⁺ was less depleted from hydrophobic polymer/water interfaces than any of the monovalent Hofmeister metal cations or even Ca²⁺ and Mg²⁺. As such, it should be placed on the far-right side of the cationic Hofmeister series. On the other hand, OH^- was excluded from the interface and could be positioned in the anionic Hofmeister series between H₂PO₄^- and SO₄^2-.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":"726-735"},"PeriodicalIF":2.8,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142906313","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}