Pub Date : 2024-09-19Epub Date: 2024-09-04DOI: 10.1021/acs.jpcb.4c05572
Pawel Wolski, Tomasz Panczyk
Poly(amidoamine) dendrimer (PAMAM)/carbon quantum dot (CQD) nanohybrids are promising candidates for many biomedical applications, including drug delivery. Effectively designing a hybrid nanocarrier requires a deep understanding of the interactions of the hybrid nanoparticle with the drug to ensure drug stability and therapeutic efficiency. In this study, we utilized fully atomistic molecular dynamics (MD) simulations to investigate the adsorption behavior of a doxorubicin (DOX) anticancer drug onto a zwitterion/PAMAM/CQD hybrid nanocarrier. The hybrid nanoparticles were composed of CQD, at two oxidation levels, grafted with PAMAM dendrimers of generation 3 (G3) or 4 (G4) decorated with zwitterion monomers. Our work reveals that the generation of the grafted dendrimer was the primary determinant of efficient adsorption of DOX, unlike the oxidation level of CQD or dendrimer surface chemistry. After grafting, the G4 dendrimers assume a more stretched conformation compared to the G3 dendrimers. This allowed DOX molecules to penetrate inside the dendritic cavities of G4 dendrimers, resulting in enhanced drug protection. The hydrophobic interaction, between the aromatic structure of DOX molecules and the nonpolar parts of dendrimers, has been proven to play a crucial role in mediating the adsorption of drug molecules. These findings provide valuable insights to assist in the design of a zwitterion/PAMAM/CQD hybrid nanoplatform for drug delivery applications.
{"title":"Insight Into Interfacial Behaviors between Doxorubicin and Zwitterion/PAMAM/CQD Hybrid Nanocarrier. A Molecular Dynamics Simulations Study.","authors":"Pawel Wolski, Tomasz Panczyk","doi":"10.1021/acs.jpcb.4c05572","DOIUrl":"10.1021/acs.jpcb.4c05572","url":null,"abstract":"<p><p>Poly(amidoamine) dendrimer (PAMAM)/carbon quantum dot (CQD) nanohybrids are promising candidates for many biomedical applications, including drug delivery. Effectively designing a hybrid nanocarrier requires a deep understanding of the interactions of the hybrid nanoparticle with the drug to ensure drug stability and therapeutic efficiency. In this study, we utilized fully atomistic molecular dynamics (MD) simulations to investigate the adsorption behavior of a doxorubicin (DOX) anticancer drug onto a zwitterion/PAMAM/CQD hybrid nanocarrier. The hybrid nanoparticles were composed of CQD, at two oxidation levels, grafted with PAMAM dendrimers of generation 3 (G3) or 4 (G4) decorated with zwitterion monomers. Our work reveals that the generation of the grafted dendrimer was the primary determinant of efficient adsorption of DOX, unlike the oxidation level of CQD or dendrimer surface chemistry. After grafting, the G4 dendrimers assume a more stretched conformation compared to the G3 dendrimers. This allowed DOX molecules to penetrate inside the dendritic cavities of G4 dendrimers, resulting in enhanced drug protection. The hydrophobic interaction, between the aromatic structure of DOX molecules and the nonpolar parts of dendrimers, has been proven to play a crucial role in mediating the adsorption of drug molecules. These findings provide valuable insights to assist in the design of a zwitterion/PAMAM/CQD hybrid nanoplatform for drug delivery applications.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142131212","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}
Pub Date : 2024-09-19Epub Date: 2024-08-01DOI: 10.1021/acs.jpcb.4c01492
Christopher D M Hutchison, Samuel Perrett, Jasper J van Thor
Free electron lasers operating in the soft and hard X-ray regime provide capabilities for ultrafast science in many areas, including X-ray spectroscopy, diffractive imaging, solution and material scattering, and X-ray crystallography. Ultrafast time-resolved applications in the picosecond, femtosecond, and attosecond regimes are often possible using single-shot experimental configurations. Aside from X-ray pump and X-ray probe measurements, all other types of ultrafast experiments require the synchronized operation of pulsed laser excitation for resonant or nonresonant pumping. This Perspective focuses on the opportunities for the optical control of structural dynamics by applying techniques from nonlinear spectroscopy to ultrafast X-ray experiments. This typically requires the synthesis of two or more optical pulses with full control of pulse and interpulse parameters. To this end, full characterization of the femtosecond optical pulses is also highly desirable. It has recently been shown that two-color and two-pulse femtosecond excitation of fluorescent protein crystals allowed a Tannor-Rice coherent control experiment, performed under characterized conditions. Pulse shaping and the ability to synthesize multicolor and multipulse conditions are highly desirable and would enable XFEL facilities to offer capabilities for structural dynamics. This Perspective will give a summary of examples of the types of experiments that could be achieved, and it will additionally summarize the laser, pulse shaping, and characterization that would be recommended as standard equipment for time-resolved XFEL beamlines, with an emphasis on ultrafast time-resolved serial femtosecond crystallography.
在软X射线和硬X射线系统中运行的自由电子激光器为许多领域的超快科学提供了能力,包括X射线光谱学、衍射成像、溶液和材料散射以及X射线晶体学。在皮秒、飞秒和阿秒级的超快时间分辨应用中,通常可以使用单次实验配置。除了 X 射线泵浦和 X 射线探针测量之外,所有其他类型的超快实验都需要同步运行脉冲激光激励,以实现共振或非共振泵浦。本视角重点关注将非线性光谱学技术应用于超快 X 射线实验,从而对结构动力学进行光学控制的机会。这通常需要合成两个或多个光脉冲,并对脉冲和脉冲间参数进行全面控制。为此,全面鉴定飞秒光脉冲也是非常理想的。最近的研究表明,对荧光蛋白晶体进行双色双脉冲飞秒激发,可以在特征条件下进行坦诺-里斯相干控制实验。脉冲整形以及合成多色和多脉冲条件的能力是非常理想的,这将使 XFEL 设备能够提供结构动力学能力。本视角将概述可实现的实验类型,还将概述作为时间分辨 XFEL 光束线标准设备推荐的激光器、脉冲整形和表征,重点是超快时间分辨串行飞秒晶体学。
{"title":"XFEL Beamline Optical Instrumentation for Ultrafast Science.","authors":"Christopher D M Hutchison, Samuel Perrett, Jasper J van Thor","doi":"10.1021/acs.jpcb.4c01492","DOIUrl":"10.1021/acs.jpcb.4c01492","url":null,"abstract":"<p><p>Free electron lasers operating in the soft and hard X-ray regime provide capabilities for ultrafast science in many areas, including X-ray spectroscopy, diffractive imaging, solution and material scattering, and X-ray crystallography. Ultrafast time-resolved applications in the picosecond, femtosecond, and attosecond regimes are often possible using single-shot experimental configurations. Aside from X-ray pump and X-ray probe measurements, all other types of ultrafast experiments require the synchronized operation of pulsed laser excitation for resonant or nonresonant pumping. This Perspective focuses on the opportunities for the optical control of structural dynamics by applying techniques from nonlinear spectroscopy to ultrafast X-ray experiments. This typically requires the synthesis of two or more optical pulses with full control of pulse and interpulse parameters. To this end, full characterization of the femtosecond optical pulses is also highly desirable. It has recently been shown that two-color and two-pulse femtosecond excitation of fluorescent protein crystals allowed a Tannor-Rice coherent control experiment, performed under characterized conditions. Pulse shaping and the ability to synthesize multicolor and multipulse conditions are highly desirable and would enable XFEL facilities to offer capabilities for structural dynamics. This Perspective will give a summary of examples of the types of experiments that could be achieved, and it will additionally summarize the laser, pulse shaping, and characterization that would be recommended as standard equipment for time-resolved XFEL beamlines, with an emphasis on ultrafast time-resolved serial femtosecond crystallography.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11421085/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141858330","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}
Pub Date : 2024-09-19Epub Date: 2024-09-06DOI: 10.1021/acs.jpcb.4c03397
Valerio Piomponi, Miroslav Krepl, Jiri Sponer, Giovanni Bussi
N6-Methyladenosine (m6A) is a prevalent RNA post-transcriptional modification that plays crucial roles in RNA stability, structural dynamics, and interactions with proteins. The YT521-B (YTH) family of proteins, which are notable m6A readers, functions through its highly conserved YTH domain. Recent structural investigations and molecular dynamics (MD) simulations have shed light on the mechanism of recognition of m6A by the YTHDC1 protein. Despite advancements, using MD to predict the stabilization induced by m6A on the free energy of binding between RNA and YTH proteins remains challenging due to inaccuracy of the employed force field and limited sampling. For instance, simulations often fail to sufficiently capture the hydration dynamics of the binding pocket. This study addresses these challenges through an innovative methodology that integrates metadynamics, alchemical simulations, and force-field refinement. Importantly, our research identifies hydration of the binding pocket as giving only a minor contribution to the binding free energy and emphasizes the critical importance of precisely tuning force-field parameters to experimental data. By employing a fitting strategy built on alchemical calculations, we refine the m6A partial charge parameters, thereby enabling the simultaneous reproduction of N6 methylation on both the protein binding free energy and the thermodynamic stability of nine RNA duplexes. Our findings underscore the sensitivity of binding free energies to partial charges, highlighting the necessity for thorough parametrization and validation against experimental observations across a range of structural contexts.
{"title":"Molecular Simulations to Investigate the Impact of N6-Methylation in RNA Recognition: Improving Accuracy and Precision of Binding Free Energy Prediction.","authors":"Valerio Piomponi, Miroslav Krepl, Jiri Sponer, Giovanni Bussi","doi":"10.1021/acs.jpcb.4c03397","DOIUrl":"10.1021/acs.jpcb.4c03397","url":null,"abstract":"<p><p>N6-Methyladenosine (m<sup>6</sup>A) is a prevalent RNA post-transcriptional modification that plays crucial roles in RNA stability, structural dynamics, and interactions with proteins. The YT521-B (YTH) family of proteins, which are notable m<sup>6</sup>A readers, functions through its highly conserved YTH domain. Recent structural investigations and molecular dynamics (MD) simulations have shed light on the mechanism of recognition of m<sup>6</sup>A by the YTHDC1 protein. Despite advancements, using MD to predict the stabilization induced by m<sup>6</sup>A on the free energy of binding between RNA and YTH proteins remains challenging due to inaccuracy of the employed force field and limited sampling. For instance, simulations often fail to sufficiently capture the hydration dynamics of the binding pocket. This study addresses these challenges through an innovative methodology that integrates metadynamics, alchemical simulations, and force-field refinement. Importantly, our research identifies hydration of the binding pocket as giving only a minor contribution to the binding free energy and emphasizes the critical importance of precisely tuning force-field parameters to experimental data. By employing a fitting strategy built on alchemical calculations, we refine the m<sup>6</sup>A partial charge parameters, thereby enabling the simultaneous reproduction of N6 methylation on both the protein binding free energy and the thermodynamic stability of nine RNA duplexes. Our findings underscore the sensitivity of binding free energies to partial charges, highlighting the necessity for thorough parametrization and validation against experimental observations across a range of structural contexts.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142138641","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}
In-cell electron paramagnetic resonance (EPR) spectroscopy experiments provide high-resolution data about conformational changes of proteins within the cell. However, one of the limitations of EPR is the requisite of stable paramagnetic centers in a reducing environment. We recently showed that histidine-rich sites in proteins hold a high affinity to Cu(II) ions complexed with a chelator. Using a chelator prevents the reduction of Cu(II) ions. Moreover, this spin-labeling methodology can be performed within the native cellular environment on any overexpressed protein without protein purification and delivery to the cell. Herein, we use this novel methodology to gain spatial information on the extracellular domain of the human copper transporter, hCtr1. Limited structural information on the transmembrane domain of the human Ctr1 (hCtr1) was obtained using X-ray crystallography and cryo-EM. However, these structures are missing information on the disordered extracellular domains of hCtr1. Extracellular domains are sensing or interacting with the environment outside of the cell and therefore play an essential role in any transmembrane protein. Especially in hCtr1, the extracellular domain functions as a gating mechanism for copper ions. Here, we performed EPR experiments revealing structural information about the extracellular N-terminal domain of the full-length hCtr1 in vitro and in situ in insect cells and cell membrane fragments. The comparison revealed that the extracellular domains of the in situ and native membrane hCtr1 are further apart than the structure of the purified protein. These method-related differences highlight the significance of studying membrane proteins in their native environment.
细胞内电子顺磁共振(EPR)光谱实验可提供有关细胞内蛋白质构象变化的高分辨率数据。然而,EPR 的局限性之一是必须在还原环境中具有稳定的顺磁中心。我们最近发现,蛋白质中富含组氨酸的位点与螯合剂络合的铜(II)离子具有很高的亲和力。使用螯合剂可以防止铜(II)离子被还原。此外,这种自旋标记方法可以在原生细胞环境中对任何过表达的蛋白质进行标记,而无需对蛋白质进行纯化并输送到细胞中。在这里,我们利用这种新方法获得了人类铜转运体 hCtr1 细胞外结构域的空间信息。利用 X 射线晶体学和低温电子显微镜获得了人类 Ctr1(hCtr1)跨膜结构域的有限结构信息。然而,这些结构缺少有关 hCtr1 紊乱的胞外结构域的信息。胞外结构域能感知细胞外的环境或与细胞外的环境相互作用,因此在任何跨膜蛋白中都起着至关重要的作用。特别是在 hCtr1 中,胞外结构域起着铜离子门控机制的作用。在这里,我们进行了 EPR 实验,揭示了全长 hCtr1 细胞外 N 端结构域在体外和原位昆虫细胞及细胞膜片段中的结构信息。比较发现,原位和原生膜 hCtr1 的胞外结构域比纯化蛋白的结构相距更远。这些与方法有关的差异凸显了在原生环境中研究膜蛋白的重要性。
{"title":"Tracking Disordered Extracellular Domains of Membrane Proteins in the Cell with Cu(II)-Based Spin Labels.","authors":"Shelly Meron, Shahaf Peleg, Yulia Shenberger, Lukas Hofmann, Lada Gevorkyan-Airapetov, Sharon Ruthstein","doi":"10.1021/acs.jpcb.4c03676","DOIUrl":"10.1021/acs.jpcb.4c03676","url":null,"abstract":"<p><p><i>In-cell</i> electron paramagnetic resonance (EPR) spectroscopy experiments provide high-resolution data about conformational changes of proteins within the cell. However, one of the limitations of EPR is the requisite of stable paramagnetic centers in a reducing environment. We recently showed that histidine-rich sites in proteins hold a high affinity to Cu(II) ions complexed with a chelator. Using a chelator prevents the reduction of Cu(II) ions. Moreover, this spin-labeling methodology can be performed within the native cellular environment on any overexpressed protein without protein purification and delivery to the cell. Herein, we use this novel methodology to gain spatial information on the extracellular domain of the human copper transporter, hCtr1. Limited structural information on the transmembrane domain of the human Ctr1 (hCtr1) was obtained using X-ray crystallography and cryo-EM. However, these structures are missing information on the disordered extracellular domains of hCtr1. Extracellular domains are sensing or interacting with the environment outside of the cell and therefore play an essential role in any transmembrane protein. Especially in hCtr1, the extracellular domain functions as a gating mechanism for copper ions. Here, we performed EPR experiments revealing structural information about the extracellular N-terminal domain of the full-length hCtr1 in vitro and in situ in insect cells and cell membrane fragments. The comparison revealed that the extracellular domains of the in situ and native membrane hCtr1 are further apart than the structure of the purified protein. These method-related differences highlight the significance of studying membrane proteins in their native environment.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11421077/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142131216","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}
Pub Date : 2024-09-18DOI: 10.1021/acs.jpcb.4c04608
Tejasvi Naik, Daria V. Berdnikova, Mahesh Sundararajan, Sharmistha Dutta Choudhury
The interaction of a styryl(pyridinium)-chromene hybrid dye (DSP-C) with the 2-hydroxypropyl-β-cyclodextrin (HPβCD) macrocycle leads to a remarkably large increase (∼310-fold) in its fluorescence intensity, in contrast to the relatively smaller (∼45-fold) enhancement observed with native β-cyclodextrin (βCD). Both macrocycles (βCD and HPβCD) bind with the styryl(pyridinium) as well as the chromene fragments of the hybrid dye, with the simultaneous formation of 1:1 and 2:1 host:guest complexes. However, the binding constant (Keq 1) is more than an order of magnitude higher for HPβCD than for βCD. The improved binding affinity of HPβCD is attributed to its elongated and deeper hydrophobic cavity. This is supported well by the optimized geometries of the host–guest complexes. Theoretical calculations also reveal that the energy change due to the release of high-energy water molecules from the host nanocavity is more favorable for HPβCD than βCD, resulting in greater stability of the HPβCD:DSP-C complex. Interestingly, though the fluorescence of DSP-C arises from its styryl(pyridinium) fragment, the complexation of the chromene unit with the host plays a major role in augmenting the fluorescence enhancement of the hybrid dye. The large fluorescence change in the HPβCD:DSP-C system has been utilized for the detection of bile salts by the indicator displacement strategy.
{"title":"Manifold Fluorescence Enhancement of a Styryl(pyridinium)-chromene Hybrid Dye upon Binding with an Elongated β-Cyclodextrin Cavity","authors":"Tejasvi Naik, Daria V. Berdnikova, Mahesh Sundararajan, Sharmistha Dutta Choudhury","doi":"10.1021/acs.jpcb.4c04608","DOIUrl":"https://doi.org/10.1021/acs.jpcb.4c04608","url":null,"abstract":"The interaction of a styryl(pyridinium)-chromene hybrid dye (DSP-C) with the 2-hydroxypropyl-β-cyclodextrin (HPβCD) macrocycle leads to a remarkably large increase (∼310-fold) in its fluorescence intensity, in contrast to the relatively smaller (∼45-fold) enhancement observed with native β-cyclodextrin (βCD). Both macrocycles (βCD and HPβCD) bind with the styryl(pyridinium) as well as the chromene fragments of the hybrid dye, with the simultaneous formation of 1:1 and 2:1 host:guest complexes. However, the binding constant (K<sub>eq 1</sub>) is more than an order of magnitude higher for HPβCD than for βCD. The improved binding affinity of HPβCD is attributed to its elongated and deeper hydrophobic cavity. This is supported well by the optimized geometries of the host–guest complexes. Theoretical calculations also reveal that the energy change due to the release of high-energy water molecules from the host nanocavity is more favorable for HPβCD than βCD, resulting in greater stability of the HPβCD:DSP-C complex. Interestingly, though the fluorescence of DSP-C arises from its styryl(pyridinium) fragment, the complexation of the chromene unit with the host plays a major role in augmenting the fluorescence enhancement of the hybrid dye. The large fluorescence change in the HPβCD:DSP-C system has been utilized for the detection of bile salts by the indicator displacement strategy.","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":null,"pages":null},"PeriodicalIF":2.991,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258610","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}
Pub Date : 2024-09-18DOI: 10.1021/acs.jpcb.4c04456
Maximilian Fleck, Samir Darouich, Niels Hansen, Joachim Gross
This study extends the transferable anisotropic Mie potential (TAMie) to alkanethiols. The force field parameters are optimized by using an analytic equation of state as a surrogate model. Given the lack of experimental density data at elevated temperatures where Monte Carlo simulations have high statistical precision, the equation of state is supplemented by a linear multifidelity Gaussian process approach to bridge the temperature gap. Force field parameters are adjusted by minimizing squared deviations of calculated vapor pressures and liquid densities from experimental data of 1-propanethiol, 1-butanethiol and 1-pentanethiol leading to small mean absolute relative deviations in liquid densities and vapor pressures. The force field is transferable to higher 1-thiols, as shown for 1-hexanethiol and 1-octanethiol. Individual parameter sets are provided for methanethiol and ethanethiol. The shear viscosity of pure substances is predicted in fair agreement with experimental data, considering that it is not included in the parametrization. Further, the phase behavior of binary mixtures of alkanethiols with alkanes is studied, and predictions of the TAMie model are found in excellent agreement with experimental data.
{"title":"TAMie Force Field for Alkanethiols: Multifidelity Gaussian Processes for Dealing with Scarce Experimental Data","authors":"Maximilian Fleck, Samir Darouich, Niels Hansen, Joachim Gross","doi":"10.1021/acs.jpcb.4c04456","DOIUrl":"https://doi.org/10.1021/acs.jpcb.4c04456","url":null,"abstract":"This study extends the transferable anisotropic Mie potential (TAMie) to alkanethiols. The force field parameters are optimized by using an analytic equation of state as a surrogate model. Given the lack of experimental density data at elevated temperatures where Monte Carlo simulations have high statistical precision, the equation of state is supplemented by a linear multifidelity Gaussian process approach to bridge the temperature gap. Force field parameters are adjusted by minimizing squared deviations of calculated vapor pressures and liquid densities from experimental data of 1-propanethiol, 1-butanethiol and 1-pentanethiol leading to small mean absolute relative deviations in liquid densities and vapor pressures. The force field is transferable to higher 1-thiols, as shown for 1-hexanethiol and 1-octanethiol. Individual parameter sets are provided for methanethiol and ethanethiol. The shear viscosity of pure substances is predicted in fair agreement with experimental data, considering that it is not included in the parametrization. Further, the phase behavior of binary mixtures of alkanethiols with alkanes is studied, and predictions of the TAMie model are found in excellent agreement with experimental data.","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":null,"pages":null},"PeriodicalIF":2.991,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258607","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}
Pub Date : 2024-09-18DOI: 10.1021/acs.jpcb.4c05106
Nikolaos I. Sigalas, Stan A. T. van Kraaij, Fotis Venetsanos, Stefanos D. Anogiannakis, Doros N. Theodorou, Alexey V. Lyulin
The test particle insertion method is used to study the solubility of oxygen in two commonly used polymers: polyethylene (PE) and isotactic polypropylene (iPP). Amorphous samples for both polymers were prepared by means of Monte Carlo and molecular dynamics simulations, and the oxygen solubility was measured across different temperatures. The solubility-temperature dependence for iPP proved to be nonmonotonic due to the interplay between binding and reorganizational enthalpy, while for PE, it appeared to be monotonic based on the available data in the studied temperature range. A broad comparison to experiments and simulations is included. Further oxygen insertions were also performed in semicrystalline PE and iPP samples at ambient temperature, and the obtained values were compared to a linear relationship which correlates the solubility in the purely amorphous phase with the solubility in the crystalline phase. The solubility of PE closely follows the linear relationship, while iPP exhibits some divergence. All the semicrystalline samples were previously annealed at elevated temperatures for long periods (a few μs), and a strong effect of annealing was observed on the structure and the solubility of iPP. A well-developed iPP lamellar structure emerged at longer annealing times, while PE develops that structure already in the early crystallization stages. The solubility of semicrystalline iPP samples with lamellar morphology exhibited better agreement with extrapolated solubility values of the amorphous state─the extrapolation was made using a linear relationship connecting solubility in the purely amorphous phase and solubility in mixed phases (amorphous and crystalline). Results on the correlation of the solubility with the local structural ordering are also present.
{"title":"Measuring Oxygen Solubility in Amorphous and Semicrystalline Polyolefins Using Test Particle Insertion: A Comparative Study of Polyethylene and Isotactic Polypropylene","authors":"Nikolaos I. Sigalas, Stan A. T. van Kraaij, Fotis Venetsanos, Stefanos D. Anogiannakis, Doros N. Theodorou, Alexey V. Lyulin","doi":"10.1021/acs.jpcb.4c05106","DOIUrl":"https://doi.org/10.1021/acs.jpcb.4c05106","url":null,"abstract":"The test particle insertion method is used to study the solubility of oxygen in two commonly used polymers: polyethylene (PE) and isotactic polypropylene (iPP). Amorphous samples for both polymers were prepared by means of Monte Carlo and molecular dynamics simulations, and the oxygen solubility was measured across different temperatures. The solubility-temperature dependence for iPP proved to be nonmonotonic due to the interplay between binding and reorganizational enthalpy, while for PE, it appeared to be monotonic based on the available data in the studied temperature range. A broad comparison to experiments and simulations is included. Further oxygen insertions were also performed in semicrystalline PE and iPP samples at ambient temperature, and the obtained values were compared to a linear relationship which correlates the solubility in the purely amorphous phase with the solubility in the crystalline phase. The solubility of PE closely follows the linear relationship, while iPP exhibits some divergence. All the semicrystalline samples were previously annealed at elevated temperatures for long periods (a few μs), and a strong effect of annealing was observed on the structure and the solubility of iPP. A well-developed iPP lamellar structure emerged at longer annealing times, while PE develops that structure already in the early crystallization stages. The solubility of semicrystalline iPP samples with lamellar morphology exhibited better agreement with extrapolated solubility values of the amorphous state─the extrapolation was made using a linear relationship connecting solubility in the purely amorphous phase and solubility in mixed phases (amorphous and crystalline). Results on the correlation of the solubility with the local structural ordering are also present.","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":null,"pages":null},"PeriodicalIF":2.991,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258947","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}
Pub Date : 2024-09-18DOI: 10.1021/acs.jpcb.4c05049
Susmita Sarkar, Anku Guha, Tharangattu N. Narayanan, Jagannath Mondal
Natural selection has driven the convergence toward a selected set of osmolytes, endowing them with the necessary efficiency to manage stress arising from salt diversity. This study combines atomistic simulations and experiments to investigate how two osmolytes, glycine and betaine, individually modulate the Hofmeister ion ordering of alkali metal salts (LiCl, KCl, and CsCl) near a charged silica interface. Both osmolytes are found to prevent salt-induced aggregation of the charged entities, yet their mode and degree of relative modulation depend on their intricate interplay with specific salt cations. Betaine’s ion-mediated surface interaction maintains Hofmeister ion ordering, whereas glycine alters the relative Hofmeister order of the cation by salt-specific ion desorption from the surface. Experimental validation through surface-enhanced Raman spectroscopy supports these findings, elucidating osmolyte-mediated alterations in interfacial water structures. These observations based on an inorganic interface are reciprocated in amyloid beta 40 dimerization dynamics, highlighting osmolytes’ efficacy in mitigating salt-induced aggregation. A molecular analysis suggests that the differential modes of interaction, as found here for glycine and betaine, are prevalent across classes of zwitterionic osmolytes.
{"title":"Osmolyte-Induced Modulation of Hofmeister Series","authors":"Susmita Sarkar, Anku Guha, Tharangattu N. Narayanan, Jagannath Mondal","doi":"10.1021/acs.jpcb.4c05049","DOIUrl":"https://doi.org/10.1021/acs.jpcb.4c05049","url":null,"abstract":"Natural selection has driven the convergence toward a selected set of osmolytes, endowing them with the necessary efficiency to manage stress arising from salt diversity. This study combines atomistic simulations and experiments to investigate how two osmolytes, glycine and betaine, individually modulate the Hofmeister ion ordering of alkali metal salts (LiCl, KCl, and CsCl) near a charged silica interface. Both osmolytes are found to prevent salt-induced aggregation of the charged entities, yet their mode and degree of relative modulation depend on their intricate interplay with specific salt cations. Betaine’s ion-mediated surface interaction maintains Hofmeister ion ordering, whereas glycine alters the relative Hofmeister order of the cation by salt-specific ion desorption from the surface. Experimental validation through surface-enhanced Raman spectroscopy supports these findings, elucidating osmolyte-mediated alterations in interfacial water structures. These observations based on an inorganic interface are reciprocated in amyloid beta 40 dimerization dynamics, highlighting osmolytes’ efficacy in mitigating salt-induced aggregation. A molecular analysis suggests that the differential modes of interaction, as found here for glycine and betaine, are prevalent across classes of zwitterionic osmolytes.","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":null,"pages":null},"PeriodicalIF":2.991,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258609","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}
Pub Date : 2024-09-18DOI: 10.1021/acs.jpcb.4c0440510.1021/acs.jpcb.4c04405
Kõu Timpmann, Margus Rätsep, Erko Jalviste and Arvi Freiberg*,
Hydrogen bonding plays a crucial role in stabilizing proteins throughout their folding process. In photosynthetic light-harvesting chromoproteins, enriched with pigment chromophores, hydrogen bonds also fine-tune optical absorption to align with the solar irradiation spectrum. Despite its significance for photosynthesis, the precise mechanism of spectral tuning through hydrogen bonding remains inadequately understood. This study investigates wild-type and genetically engineered LH2 and LH1 light-harvesting complexes from Rhodobacter sphaeroides using a unique set of advanced spectroscopic techniques combined with simple exciton modeling. Our findings reveal an intricate interplay between exciton and site energy shift mechanisms, challenging the prevailing belief that spectral changes observed in these complexes upon the modification of tertiary structure hydrogen bonds almost directly follow shifting site energies. These deeper insights into natural adaptation processes hold great promise for advancing sustainable solar energy conversion technologies.
{"title":"Tuning by Hydrogen Bonding in Photosynthesis","authors":"Kõu Timpmann, Margus Rätsep, Erko Jalviste and Arvi Freiberg*, ","doi":"10.1021/acs.jpcb.4c0440510.1021/acs.jpcb.4c04405","DOIUrl":"https://doi.org/10.1021/acs.jpcb.4c04405https://doi.org/10.1021/acs.jpcb.4c04405","url":null,"abstract":"<p >Hydrogen bonding plays a crucial role in stabilizing proteins throughout their folding process. In photosynthetic light-harvesting chromoproteins, enriched with pigment chromophores, hydrogen bonds also fine-tune optical absorption to align with the solar irradiation spectrum. Despite its significance for photosynthesis, the precise mechanism of spectral tuning through hydrogen bonding remains inadequately understood. This study investigates wild-type and genetically engineered LH2 and LH1 light-harvesting complexes from <i>Rhodobacter sphaeroides</i> using a unique set of advanced spectroscopic techniques combined with simple exciton modeling. Our findings reveal an intricate interplay between exciton and site energy shift mechanisms, challenging the prevailing belief that spectral changes observed in these complexes upon the modification of tertiary structure hydrogen bonds almost directly follow shifting site energies. These deeper insights into natural adaptation processes hold great promise for advancing sustainable solar energy conversion technologies.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/acs.jpcb.4c04405","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142318084","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}
Pub Date : 2024-09-18DOI: 10.1021/acs.jpcb.4c02460
Aaron G. Feinstein, James L. Cole, Eric R. May
Protein kinase R (PKR) functions in the eukaryotic innate immune system as a first-line defense against viral infections. PKR binds viral dsRNA, leading to autophosphorylation and activation. In its active state, PKR can phosphorylate its primary substrate, eIF2α, which blocks the initiation of translation in the infected cell. It has been established that PKR activation occurs when the kinase domain dimerizes in a back-to-back configuration. However, the mechanism by which dimerization leads to enzymatic activation is not fully understood. Here, we investigate the structural mechanistic basis and energy landscape for PKR activation, with a focus on the αC helix─a kinase activation and signal integration hub─using all-atom equilibrium and enhanced sampling molecular dynamics simulations. By employing window-exchange umbrella sampling, we compute free-energy profiles of activation, which show that back-to-back dimerization stabilizes a catalytically competent conformation of PKR. Key hydrophobic residues in the homodimer interface contribute to stabilization of the αC helix in an active conformation and the position of its critical glutamate residue. Using linear mutual information analysis, we analyze allosteric communication connecting the protomers’ N-lobes and the αC helix dimer interface with the αC helix.
蛋白激酶 R(PKR)在真核生物先天免疫系统中发挥着抵御病毒感染的第一道防线的作用。PKR 与病毒 dsRNA 结合,导致自身磷酸化和激活。在活性状态下,PKR 可使其主要底物 eIF2α 磷酸化,从而阻止受感染细胞的翻译启动。已经证实,当激酶结构域以背靠背的形式二聚时,PKR 就会被激活。然而,二聚化导致酶激活的机制尚未完全清楚。在这里,我们利用全原子平衡和增强采样分子动力学模拟研究了 PKR 激活的结构机理基础和能量图谱,重点是 αC 螺旋--激酶激活和信号整合枢纽。通过采用窗口交换伞状取样,我们计算了激活的自由能曲线,结果表明背靠背二聚化能稳定 PKR 的催化构象。同源二聚体界面中的关键疏水残基有助于稳定活性构象中的αC螺旋及其关键谷氨酸残基的位置。通过线性互信息分析,我们分析了连接原生体 N 叶和αC 螺旋二聚体界面与αC 螺旋的异构通讯。
{"title":"Dimerization Promotes PKR Activation by Modulating Energetics of αC Helix Conversion between Active and Inactive Conformations","authors":"Aaron G. Feinstein, James L. Cole, Eric R. May","doi":"10.1021/acs.jpcb.4c02460","DOIUrl":"https://doi.org/10.1021/acs.jpcb.4c02460","url":null,"abstract":"Protein kinase R (PKR) functions in the eukaryotic innate immune system as a first-line defense against viral infections. PKR binds viral dsRNA, leading to autophosphorylation and activation. In its active state, PKR can phosphorylate its primary substrate, eIF2α, which blocks the initiation of translation in the infected cell. It has been established that PKR activation occurs when the kinase domain dimerizes in a back-to-back configuration. However, the mechanism by which dimerization leads to enzymatic activation is not fully understood. Here, we investigate the structural mechanistic basis and energy landscape for PKR activation, with a focus on the αC helix─a kinase activation and signal integration hub─using all-atom equilibrium and enhanced sampling molecular dynamics simulations. By employing window-exchange umbrella sampling, we compute free-energy profiles of activation, which show that back-to-back dimerization stabilizes a catalytically competent conformation of PKR. Key hydrophobic residues in the homodimer interface contribute to stabilization of the αC helix in an active conformation and the position of its critical glutamate residue. Using linear mutual information analysis, we analyze allosteric communication connecting the protomers’ N-lobes and the αC helix dimer interface with the αC helix.","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":null,"pages":null},"PeriodicalIF":2.991,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258608","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}