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Smart materials enabling emission intensity or wavelength tuning by light stimulus have attracted attention in cutting‐edge fields. However, due to the general limitation of the dense molecular stacking (in solid states, especially in crystals) on photoresponsivity, constructing rapidly phototunable solid‐state luminescent systems remains challenging. Herein, we present a new luminophore that serves as both a photoresponsive and a luminous group with enhanced conformational freedom to attain this goal, namely, relying on photoexcitation‐induced molecular conformational change of an ionized persulfurated arene based on weak intermolecular aliphatic C−H⋅⋅⋅π interaction. Together with the phosphorescence characteristic of the molecule itself, rapidly enhanced phosphorescence upon irradiation can be observed in a series of phase states, like solution state, crystal, and amorphous state, especially with a high photoresponsive rate of 0.033 s−1 in crystal state that is superior to the relevant reported cases. Moreover, a rapidly phototunable afterglow effect is achieved by extending this molecule into some polymer‐based doping systems, endowing the system with unique dynamic imaging and fast photopatterning capabilities. This single‐luminophore molecular engineering and underlying mechanism have implications for building other condensed functional materials, principally for those with stimuli responses in solid states. [ABSTRACT FROM AUTHOR]

Ultrahigh dose-rate (FLASH) radiotherapy is an emerging technology with excellent therapeutic effects and low biological toxicity. However, tumor recurrence largely impede the effectiveness of FLASH therapy. Overcoming tumor recurrence is crucial for practical FLASH applications. Here, we prepared an agarose-based thermosensitive hydrogel containing a mild photothermal agent (TPE-BBT) and a glutaminase inhibitor (CB-839). Within nanoparticles, TPE-BBT exhibits aggregation-induced emission peaked at 900 nm, while the unrestricted molecular motions endow TPE-BBT with a mild photothermy generation ability. The balanced photothermal effect and photoluminescence are ideal for phototheranostics. Upon 660-nm laser irradiation, the temperature-rising effect softens and hydrolyzes the hydrogel to release TPE-BBT and CB-839 into the tumor site for concurrent mild photothermal therapy and chemotherapy, jointly inhibiting homologous recombination repair of DNA. The enhanced FLASH radiotherapy efficiently kills the tumor tissue without recurrence and obvious systematic toxicity. This work deciphers the unrestricted molecular motions in bright organic fluorophores as a source of photothermy, and provides novel recurrence-resistant radiotherapy without adverse side effects.

Molecules in the bulk state are typically constrained by multiple intermolecular interactions, making it challenging to develop emission‐tunable solid‐state materials. Manipulating molecular motion is essential for achieving dynamic solid‐state emissions. Herein, various emission‐tunable 4CN@polymer films are developed whose multicolor luminescence arises from different molecular motion modes within the polymer microenvironments. There are three motion modes in the films: restricted, normal, and vigorous. In the normal mode, the film emits green light, shifting to purple under UV (515–387 nm). Cooling or fuming creates a rigid environment, leading to blue emission at 426 nm. High temperatures induce vigorous motion, causing quenched emission, which can be reactivated by cooling. This mechanism underscores the significant influence of molecular motion within flexible polymers on the luminescence behavior of 4CN@polymer films, enabling multicolor emission based on environmental conditions. The wide‐range fluorescence—from purple, blue, white, green, yellow‐green to dark—indicates promising applications in multifaceted dynamic displays and information security. This study offers novel perspectives on the correlation between solid‐state molecular motion and dynamic emission. [ABSTRACT FROM AUTHOR]

Controlling the efficient emission of organic luminogens in both monomeric and various aggregated states remains a challenging task. In this work, the motion of an organic luminophores is synergistically regulated by introducing side alkyl chains with appropriate length and the aromatic rotor triphenylamine. This study finds that the incorporation of alkyl chains not only increased the rotational barriers in the molecule, but also influenced the packing modes. The as‐prepared organic luminogen, FIMPA‐C6, exhibited bright emissions in solution, polymorph, and amorphous states. Furthermore, the emission of FIMPA‐C6 can be widely tuned from yellow to deep red in different aggregated states. The exceptional luminescent properties of FIMPA‐C6 make it a promising functional dye for cellular imaging applications. [ABSTRACT FROM AUTHOR]

A shock wave is a flow phenomenon that needs to be considered in the development of high-speed aircraft and engines. The traditional computational fluid dynamics (CFD) method describes it from the perspective of macroscopic variables, such as the Mach number, pressure, density, and temperature. The thickness of the shock wave is close to the level of the molecular free path, and molecular motion has a strong influence on the shock wave. According to the analysis of the Chapman-Enskog approach, the nonequilibrium effect is the source term that causes the fluid system to deviate from the equilibrium state. The nonequilibrium effect can be used to obtain a description of the physical characteristics of shock waves that are different from the macroscopic variables. The basic idea of the nonequilibrium effect approach is to obtain the nonequilibrium moment of the molecular velocity distribution function by solving the Boltzmann–Bhatnagar–Gross–Krook (Boltzmann BGK) equations or multiple relaxation times Boltzmann (MRT-Boltzmann) equations and to explore the nonequilibrium effect near the shock wave from the molecular motion level. This article introduces the theory and understanding of the nonequilibrium effect approach and reviews the research progress of nonequilibrium behavior in shock-related flow phenomena. The role of nonequilibrium moments played on the macroscopic governing equations of fluids is discussed, the physical meaning of nonequilibrium moments is given from the perspective of molecular motion, and the relationship between nonequilibrium moments and equilibrium moments is analyzed. Studies on the nonequilibrium effects of shock problems, such as the Riemann problem, shock reflection, shock wave/boundary layer interaction, and detonation wave, are introduced. It reveals the nonequilibrium behavior of the shock wave from the mesoscopic level, which is different from the traditional macro perspective and shows the application potential of the mesoscopic kinetic approach of the nonequilibrium effect in the shock problem. [ABSTRACT FROM AUTHOR]

Molecular visualization is a powerful way to represent the complex structure of molecules and their higher order assemblies, as well as the dynamics of their interactions. Although conventions for depicting static molecular structures and complexes are now well established and guide the viewer’s attention to specific aspects of structure and function, little attention and design classification has been devoted to how molecular motion is depicted. As we continue to probe and discover how molecules move - including their internal flexibility, conformational changes and dynamic associations with binding partners and environments - we are faced with difficult design challenges that are relevant to molecular visualizations both for the scientific community and students of cell and molecular biology. To facilitate these design decisions, we have identified twelve molecular animation design principles that are important to consider when creating molecular animations. Many of these principles pertain to misconceptions that students have primarily regarding the agency of molecules, while others are derived from visual treatments frequently observed in molecular animations that may promote misconceptions. For each principle, we have created a pair of molecular animations that exemplify the principle by depicting the same content in the presence and absence of that design approach. Although not intended to be prescriptive, we hope this set of design principles can be used by the scientific, education, and scientific visualization communities to facilitate and improve the pedagogical effectiveness of molecular animation.

We designed a proline‐derived monomer with azide and alkene functional groups to enable topochemical ene‐azide cycloaddition (TEAC) polymerization. In its crystal, the monomer forms supramolecular helices along the 'a' axis through various non‐covalent interactions. Along the 'c' axis, the molecules arrange themselves head‐to‐tail in a wave‐like pattern, positioning the azide and alkene groups of adjacent molecules in close proximity and anti‐parallel orientation, complying with Schmidt's criteria for topochemical reaction. This prearranged configuration was expected to facilitate smooth topochemical polymerization, resulting in a 1,4‐triazoline‐linked polymer. Upon heating, the monomer underwent TEAC polymerization in a remarkable single‐crystal‐to‐single‐crystal fashion, but, to our surprise, it yielded an unexpected covalent helical polymer linked by 1,5‐disubstituted triazoline units. Remarkably, the crystal avoids the ready‐to‐react arrangement for polymerization, but connects monomer molecules within the supramolecular helix through the cycloaddition of azide and alkene groups, even though they are not in close proximity nor in the expected orientation. This unexpected path, involving a substantial 134° rotation of the alkene group, yields hitherto unknown 1,5‐disubstituted triazoline product regiospecifically. This study serves as a cautionary reminder that relying solely on topochemical postulates for predicting reactivity can sometimes be misleading. [ABSTRACT FROM AUTHOR]

Thermal annealing has been proven to be an efficient method to optimize the device performance of organic and polymeric opto-electronic materials. However, no detailed information of aggregate structures was obtained for a deeper understanding of what happens during thermal annealing. Herein, through modulation of molecular configurations by tunable linkage positions, and the amplified amplitudes of molecular motions by incorporation of additional methylene units, accurate changes of aggregated structures upon thermal annealing have been achieved, accompanying with the 'turn-on' room temperature phosphorescence (RTP) response by about 4800- and 177-fold increase of lifetimes. The stretching and swing motion models have been proposed, which afforded an efficient way to investigate the science of dynamic aggregation in depth. [ABSTRACT FROM AUTHOR]

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In this paper, 2H nuclear magnetic resonance (NMR) was performed to study the motions of the embedded cations in the cation-doped lead bromide perovskite (MA0.6DMA0.4PbBr3). By selectively deuterating dimethylamine (DMA) and methylammonium (MA) cations, we achieved selective NMR observations of the different embedded cations in the materials. The results show that at low temperatures, both the DMA and MA cations in the material have molecular motions close to the double rotation model. As the temperature increases, the motion freedom of the DMA and MA cations increases, and the motions gradually transform into fast isotropic motions. It was observed that the DMA cations have higher mobility than the MA cations in the same materials at the same temperature, indicating that there is a significant inhomogeneity in the states of cations in the material. Based on the study of the cation motions, the molecular mechanism of the phase transition of the material was discussed.

Thermal aging is one of the main reasons for the degradation of insulation properties of high voltage cable. Dielectric properties and breakdown strength are important parameters to reflect the insulation performance of the cable insulation materials. In the work, the influence of thermal aging on dielectric and breakdown performance of the cable insulation layer was studied. Firstly, XLPE cable insulation samples were prepared and the thermal aging treatment was carried out. Secondly, the microstructure and molecular structure of XLPE samples under different thermal aging time were analyzed. The dielectric properties and breakdown characteristics of XLPE samples under different thermal aging times were characterized in macro aspect. Finally, the effects of different temperatures on the molecular microstructure of XLPE were studied. The results show that with the extension of thermal aging time, the microstructure of XLPE molecule is destroyed, the macromolecular chain is gradually cleaved, and the carbonyl absorption intensity increases. At power frequency, the breakdown strength decreases from 75.37 kV/mm to 62.18 kV/mm, the relative permittivity increases from 2.44 to 2.51, and the dielectric loss increases from 1.47 × 10−4 to 3.10 × 10−3. The free volume rate of XLPE molecules increases with the increasing temperature, and the mean square displacement gradually increases. The work has good guiding significance for the safe operation and condition assessment of high-voltage cables. [ABSTRACT FROM AUTHOR]

A shock wave is a flow phenomenon that needs to be considered in the development of high-speed aircraft and engines. The traditional computational fluid dynamics (CFD) method describes it from the perspective of macroscopic variables, such as the Mach number, pressure, density, and temperature. The thickness of the shock wave is close to the level of the molecular free path, and molecular motion has a strong influence on the shock wave. According to the analysis of the Chapman-Enskog approach, the nonequilibrium effect is the source term that causes the fluid system to deviate from the equilibrium state. The nonequilibrium effect can be used to obtain a description of the physical characteristics of shock waves that are different from the macroscopic variables. The basic idea of the nonequilibrium effect approach is to obtain the nonequilibrium moment of the molecular velocity distribution function by solving the Boltzmann–Bhatnagar–Gross–Krook (Boltzmann BGK) equations or multiple relaxation times Boltzmann (MRT-Boltzmann) equations and to explore the nonequilibrium effect near the shock wave from the molecular motion level. This article introduces the theory and understanding of the nonequilibrium effect approach and reviews the research progress of nonequilibrium behavior in shock-related flow phenomena. The role of nonequilibrium moments played on the macroscopic governing equations of fluids is discussed, the physical meaning of nonequilibrium moments is given from the perspective of molecular motion, and the relationship between nonequilibrium moments and equilibrium moments is analyzed. Studies on the nonequilibrium effects of shock problems, such as the Riemann problem, shock reflection, shock wave/boundary layer interaction, and detonation wave, are introduced. It reveals the nonequilibrium behavior of the shock wave from the mesoscopic level, which is different from the traditional macro perspective and shows the application potential of the mesoscopic kinetic approach of the nonequilibrium effect in the shock problem.

Purpose: To evaluate and quantify inter‐directional and inter‐acquisition variation in diffusion‐weighted imaging (DWI) and emphasize signals that report restricted diffusion to enhance cancer conspicuity, while reducing the effects of local microscopic motion and magnetic field fluctuations. Methods: Ten patients with biopsy‐proven prostate cancer were studied under an Institutional Review Board‐approved protocol. Individual acquisitions of DWI signal intensities were reconstructed to calculate inter‐acquisition distributions and their statistics, which were compared for healthy versus cancer tissue. A method was proposed to detect and filter the acquisitions affected by motion‐induced signal loss. First, signals that reflect restricted diffusion were separated from the acquisitions that suffer from signal loss, likely due to microscopic motion, by imposing a cutoff value. Furthermore, corrected apparent diffusion coefficient maps were calculated by employing a weighted sum of the multiple acquisitions, instead of conventional averaging. These weights were calculated by applying a soft‐max function to the set of acquisitions per‐voxel, making the analysis immune to acquisitions with significant signal loss, even if the number of such acquisitions is high. Results: Inter‐acquisition variation is much larger than the Rician noise variance, local spatial variations, and the estimates of diffusion anisotropy based on the current data, as well as the published values of anisotropy. The proposed method increases the contrast for cancers and yields a sensitivity of 98.8%$$ 98.8\% $$ with a false positive rate of 3.9%$$ 3.9\% $$. Conclusion: Motion‐induced signal loss makes conventional signal‐averaging suboptimal and can obscure signals from areas with restricted diffusion. Filtering or weighting individual acquisitions prior to image analysis can overcome this problem. [ABSTRACT FROM AUTHOR]

Nonradiative decay invariably competes with radiative decay during the deexcitation process of matter. In the community of luminescence research, nonradiative decay has been deemed less attractive than radiative decay. However, all things in their being are good for something and so is nonradiative decay. As the molecular motion‐facilitated nonradiative decay (MMFND) effect is inevitable in photophysical processes, it provides a new avenue to convert the harvested light energy into exploitable forms by harnessing molecular motion. In many cases, active molecular motion enables thermal deactivation from excited states. In this Minireview, recent advances in photothermal and photoacoustic systems with MMFND character are summarized. We believe that this presentation of the rational engineering of molecular motion for efficient photothermal generation will deepen the understanding of the relationship between molecular motion and nonradiative decay and navigate people to rethink the positive aspects of nonradiative decay for the establishment of new light‐controllable techniques. [ABSTRACT FROM AUTHOR]

The development of direct current high-voltage power cables requires insulating materials having excellent electrically insulation properties. Experiments show that appropriate nanodoping can improve the breakdown strength of polyethylene (PE) nanocomposites. Research indicates that traps, free volumes, and molecular displacement are key factors affecting the breakdown strength. This study comprehensively considered the space charge transport, electron energy gain, and molecular chain long-distance movement during the electrical breakdown process. In addition, we established three simulation models focusing on the electric field distortion due to space charges captured by traps, the energy gain of mobile electrons in free volumes, the free volume expansion caused by long-distance movement of molecular chains under the Coulomb force, and the energy gained by the electrons moving in the enlarged free volumes. The three simulation models considered the electrical breakdown modulated by space charges, with a maximum electric field criterion and a maximum electron energy criterion, and the electrical breakdown modulated by the molecular displacement (EBMD), with a maximum electron energy criterion. These three models were utilized to simulate the breakdown strength dependent on the nanofiller content of PE nanocomposites. The simulation results of the EBMD model coincided best with the experimental results. It was revealed that the breakdown electric field of PE nanodielectrics is improved synergistically by both the strong trapping effect of traps and the strong binding effect of molecular chains in the interfacial regions. [ABSTRACT FROM AUTHOR]

Molecular motion in crystals has attracted much attention for the development of stimuli‐responsive materials. The most studied are molecules with few atoms or highly symmetrical molecules. To develop molecules with new motion characteristics, we synthesized a charge‐transfer compound, namely, tropylium hexafluoridoantimonate(V)–1,4‐dimethylnaphthalene (1/1), (C7H7)[SbF6]·C12H12, and studied its structural phase transition. In this compound, the tropylium cation and the 1,4‐dimethylnaphthalene molecule have planar geometry, but the latter has low symmetry. They are stacked as a one‐dimensional chain structure through π–π charge‐transfer interactions. Weak intermolecular interactions and planar molecular geometry result in a large degree of freedom of in‐plane motion. Upon heating, due to the in‐plane rotation of the molecules, the compound undergoes an order–disorder structural phase transition (phase‐transition temperature = 334 K). The space group of the room‐temperature phase is P21/m and the space group of the high‐temperature phase is P4/mmm. This phase transition is accompanied by significant dielectric anomalies. The current investigation shows that the structural features of the title compound can be used to construct functional materials with phase transitions, such as molecular ferroelectrics. [ABSTRACT FROM AUTHOR]

Molecular motions are ubiquitous in nature and they immutably play intrinsic roles in all actions. However, exploring appropriate models to decipher molecular motions is an extremely important but very challenging task for researchers. Considering aggregation‐induced emission (AIE) luminogens possess their unique merits to visualize molecular motions, it is particularly fascinating to construct new AIE systems as models to study molecular motion. Herein, a novel quinolizine (QLZ) AIE system was constructed based on the restriction intramolecular vibration (RIV) mechanism. It was demonstrated that QLZ could act as an ideal model to visualize single‐molecule motion and macroscopic molecular motion via fluorescence change. Additionally, further elaborate tailoring of this impressive core achieved highly efficient reactive oxygen species production and realized fluorescence imaging‐guided photodynamic therapy applications, which confirms the great application potential of this new AIE‐active QLZ core. Therefore, this work not only provides an ideal model to visualize molecular motion but also opens a new way for the application of AIEgens. [ABSTRACT FROM AUTHOR]

Molecular visualization is a powerful way to represent the complex structure of molecules and their higher order assemblies, as well as the dynamics of their interactions. Although conventions for depicting static molecular structures and complexes are now well established and guide the viewer's attention to specific aspects of structure and function, little attention and design classification has been devoted to how molecular motion is depicted. As we continue to probe and discover how molecules move - including their internal flexibility, conformational changes and dynamic associations with binding partners and environments - we are faced with difficult design challenges that are relevant to molecular visualizations both for the scientific community and students of cell and molecular biology. To facilitate these design decisions, we have identified twelve molecular animation design principles that are important to consider when creating molecular animations. Many of these principles pertain to misconceptions that students have primarily regarding the agency of molecules, while others are derived from visual treatments frequently observed in molecular animations that may promote misconceptions. For each principle, we have created a pair of molecular animations that exemplify the principle by depicting the same content in the presence and absence of that design approach. Although not intended to be prescriptive, we hope this set of design principles can be used by the scientific, education, and scientific visualization communities to facilitate and improve the pedagogical effectiveness of molecular animation., Competing Interests: Author SJ was employed by Biocinematics. Author GM was employed by Digizyme. The remaining author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Jantzen, McGill and Jenkinson.)

The development of direct current high-voltage power cables requires insulating materials having excellent electrically insulation properties. Experiments show that appropriate nanodoping can improve the breakdown strength of polyethylene (PE) nanocomposites. Research indicates that traps, free volumes, and molecular displacement are key factors affecting the breakdown strength. This study comprehensively considered the space charge transport, electron energy gain, and molecular chain long-distance movement during the electrical breakdown process. In addition, we established three simulation models focusing on the electric field distortion due to space charges captured by traps, the energy gain of mobile electrons in free volumes, the free volume expansion caused by long-distance movement of molecular chains under the Coulomb force, and the energy gained by the electrons moving in the enlarged free volumes. The three simulation models considered the electrical breakdown modulated by space charges, with a maximum electric field criterion and a maximum electron energy criterion, and the electrical breakdown modulated by the molecular displacement (EBMD), with a maximum electron energy criterion. These three models were utilized to simulate the breakdown strength dependent on the nanofiller content of PE nanocomposites. The simulation results of the EBMD model coincided best with the experimental results. It was revealed that the breakdown electric field of PE nanodielectrics is improved synergistically by both the strong trapping effect of traps and the strong binding effect of molecular chains in the interfacial regions.

The design and synthesis of a novel rotaxane/foldaxane hybrid architecture is reported. The winding of an aromatic oligoamide helix host around a dumbbell‐shaped thread‐like guest, or axle, already surrounded by a macrocycle was evidenced by NMR spectroscopy and X‐ray crystallography. The process proved to depend on the position of the macrocycle along the axle and the associated steric hindrance. The macrocycle thus behaves as a switchable shield that modulates the affinity of the helix for the axle. Reciprocally, the foldamer helix acts as a supramolecular auxiliary that compartmentalizes the axle. In some cases, the macrocycle is forced to move along the axle to allow the foldamer to reach its best recognition site. [ABSTRACT FROM AUTHOR]

Ultrahigh dose-rate (FLASH) radiotherapy is an emerging technology with excellent therapeutic effects and low biological toxicity. However, tumor recurrence largely impede the effectiveness of FLASH therapy. Overcoming tumor recurrence is crucial for practical FLASH applications. Here, we prepared an agarose-based thermosensitive hydrogel containing a mild photothermal agent (TPE-BBT) and a glutaminase inhibitor (CB-839). Within nanoparticles, TPE-BBT exhibits aggregation-induced emission peaked at 900 nm, while the unrestricted molecular motions endow TPE-BBT with a mild photothermy generation ability. The balanced photothermal effect and photoluminescence are ideal for phototheranostics. Upon 660-nm laser irradiation, the temperature-rising effect softens and hydrolyzes the hydrogel to release TPE-BBT and CB-839 into the tumor site for concurrent mild photothermal therapy and chemotherapy, jointly inhibiting homologous recombination repair of DNA. The enhanced FLASH radiotherapy efficiently kills the tumor tissue without recurrence and obvious systematic toxicity. This work deciphers the unrestricted molecular motions in bright organic fluorophores as a source of photothermy, and provides novel recurrence-resistant radiotherapy without adverse side effects., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

The advent of single-molecule atomic-resolution time-resolved electron microscopy (SMART-EM) has created a new field of 'cinematic chemistry,' allowing for the cinematographic recording of dynamic behaviors of organic and inorganic molecules and their assembly. However, the limited electron dose per frame of video images presents a major challenge in SMART-EM. Recent advances in direct electron counting cameras and techniques to enhance image quality through the implementation of a denoising algorithm have enabled the tracking of stochastic molecular motions and chemical reactions with sub-millisecond temporal resolution and sub-angstrom localization precision. This review showcases the development of dynamic molecular imaging using the SMART-EM technique, highlighting insights into nanomechanical behavior during molecular shuttle motion, pathways of multistep chemical reactions, and elucidation of crystallization processes at the atomic level., (© The Author(s) 2023. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Using reverse thinking of the aggregation‐induced emission (AIE) principle, we demonstrate an ingenious and universal protocol for amplifying molecular motions to boost photothermal efficiency of fibers. Core–shell nanofibers having the olive oil solution of AIE‐active molecules as the core surrounded by PVDF‐HFP shell were constructed by coaxial electrospinning. The molecularly dissolved state of AIE‐active molecules allows them to freely rotate and/or vibrate in nanofibers upon photoexcitation and thus significantly elevates the proportion of non‐radiative energy dissipation, affording impressive heat‐generating efficiency. Photothermal evaluation shows that the core–shell nanofibers with excellent durability can reach up to 22.36 % of photothermal conversion efficiency, which is 26‐fold as the non‐core–shell counterpart. Such a core–shell fiber can be used for photothermal textiles and solar steam generation induced by natural sunlight with green and carbon‐zero emission. [ABSTRACT FROM AUTHOR]

The influence of seven-month aging on molecular motion in blends of biodegradable poly(butylene-adipate-co-terephthalate) (PBAT) and corn starch plasticized with water, urea (U) and/or glycerol (G) was studied using solid-state 1H and 13C NMR spectroscopy. Changes in 1H and 13C NMR spectra due to aging in G-containing blends are explained by starch retrogradation. The increasing number of urea-glycerol interactions in the aged UG-containing blend can be deduced from the 1H NMR spectra. The formation of a crystalline phase was not observed in the U-containing blends. The 13C spin-lattice relaxation times and scanning electron microscopy support this interpretation of the NMR spectra. [ABSTRACT FROM AUTHOR]

Prerequisite for chemical shift (CS) and CS tensor calculations are highly refined structures defining the molecular surroundings of the nuclei under study. Here, we present geometry optimizations with 13C and 15N CS constraints for large bio-molecules like peptides and proteins. The method discussed here provides both, refined structures and chemical shift tensors. Furthermore, since the experimental resonances of aligned systems are related to CS tensors, they strongly depend on the orientation and motion of molecules, their fragments, functional groups and moieties. For efficient CS calculations we apply a semi-empirical approach—the bond polarization theory (BPT). The BPT relies on linear bond polarization parameters and we present a new set of parameters based on ab initio second-order Møller–Plesset perturbation theory calculations. The new parametrization extends the applicability of the BPT approach to a wide range of organic molecules and bio-polymers. Here, the method has been applied to the protein ubiquitin and the membrane-active peptide gramicidin A (dimer) in oriented bilayers. The calculated 13C and 15N CS values of best-refined structures published until now gave a large scatter with respect to the experiment. It will be shown that BPT CS optimizations can reduce these errors to values near the experimental uncertainty. In combination with molecular dynamics with orientational constraints it is possible to study motional dynamics and BPT calculations can provide residual chemical shift anisotropies. [ABSTRACT FROM AUTHOR]

The molecular motion of starch at different glycerol concentrations (0, 20, 50, and 80 %) was investigated using Electron Paramagnetic Resonance (EPR) spectroscopy. Fourier-transform infrared (FTIR) spectroscopy and 1H nuclear magnetic resonance (1H NMR) spectroscopy confirmed that hydroxyl groups at the C2 and C3 positions of glucose units in corn starch (CS), waxy corn starch (WCS), and high amylose corn starch (HCS) were labeled with 4-amino-TEMPO. The crystallinities of CS, WCS, and HCS after spin-labeling decreased from 30.68 % to 3.21 %, 39.36 % to 1.65 %, and 28.54 % to 8.08 %, respectively. The pseudoplastic fluid properties of the spin-labeled starch remained shear-thin at different glycerol concentrations. EPR revealed the fast- and slow-motion components of the spin-labeled starch molecules dispersed in water. At a glycerol concentration of 20 %, the slow-motion component disappeared, indicating a faster rotational motion of the starch chain segments. As the glycerol concentration increased to 50 and 80 %, the rotational motion slowed because of high viscosity. In particular, the mobility of the spin-labeled WCS chains increased owing to easier access of glycerol and water to the branched structure. This study directly observed the dynamics of the molecular behavior of starch in glycerol-water systems. • Spin-labeled starches were prepared using 4-amino-TEMPO. • Spin labels reacted with the hydroxyl groups of C2 and C3 on the glucose residues. • EPR spectra can qualitatively demonstrate starch chain segment motion. • Starch chain segments exhibit faster mobility in 20 % glycerol content. [ABSTRACT FROM AUTHOR]

[Display omitted] • The coupling mechanism of BO and VUV technology was first proposed. • BO/VUV effectively removed multiple emerging pollutants without producing secondary pollutants. • The feasibility of the BO/VUV technology was verified in actual water bodies. • BO/VUV treatment reduced tap water toxicity, securing it as a terminal drinking water treatment option. Micropollutant in drinking water may not be effectively removed during centralized treatment. To reduce potential health risks, water treatment at the user terminal is warranted. This study investigated the performance of VUV coupled with boiling to simultaneously remove contaminants, a common household water treatment method in developing countries, for the treatment of micropollutants. Compared to individual boiling or VUV treatment, the VUV/BO process was more effective in improving the degradation of micropollutants. The results showed that heating promoted the direct photolysis and HO oxidation capabilities in the VUV process, with the HO generation increasing from 36.56 μM at 30 °C to 80.48 μM at 90 °C. At a reaction temperature of 100 °C, the degradation rates of malathion (MAL), dimethoate (DMT), trichloroacetic acid (TCAA), and dichloroacetic acid (DCAA) by VUV were increased by 0.81, 1.19, 1.34, and 0.90 times respectively compared to 25 °C. Analysis of the organic composition of actual water samples showed that the total fluorescence intensity of organic matter decreased significantly after VUV oxidation, mainly degrading humic-like substances. Using GC–MS analysis, this study identified 11 oxidative products of the DMT, and proposed two possible degradation pathways. Toxicity evaluation of the intermediate products of DMT demonstrated that they were less toxic than the parent contaminants. The results indicate that the heating-coupled water treatment process provides an effective technology for the treatment of micropollutants in terminal drinking water, and this process is worth promoting in the future. [ABSTRACT FROM AUTHOR]

Hartmann–Hahn cross polarization and INEPT polarization transfer are the most popular sequences to increase the polarization of low- γ nuclei in magic-angle spinning solid-state NMR. It is well known that the two methods preferentially lead to polarization transfer in different parts of molecules. Cross polarization works best in rigid segments of the molecule while INEPT-based polarization transfer is efficient in highly mobile segments where (nearly) isotropic motion averages out the dipolar couplings. However, there have only been few attempts to define the time scales of motion that are compatible with cross polarization or INEPT transfer in a more quantitative way. We have used simple isotropic jump models in combination with simulations based on the stochastic Liouville equation to elucidate the time scales of motion that allow either cross polarization or INEPT-based polarization transfer. We investigate which motional time scales interfere with one or both polarization-transfer schemes. We have modeled isolated I-S two-spin systems, strongly-coupled I 2 S three-spin systems and more loosely coupled I–I-S three-spin systems as well as I 3 S groups. Such fragments can be used as models for typical environments in fully deuterated and back-exchanged molecules (I-S), for fully protonated molecules (I 2 S and I 3 S) or situations in between (I–I-S). [Display omitted] • The dependence of heteronuclear polarization transfer under MAS on the time scale of isotropic molecular motion is investigated. • Cross polarization under MAS is efficient for exchange rate constants smaller than approximately 1 ⋅ 10 5 s − 1 . • INEPT polarization transfer under MAS is efficient for exchange rate constants larger than approximately 1 ⋅ 10 7 s − 1 . • In the intermediate exchange regime between 1 ⋅ 10 5 s − 1 and 1 ⋅ 10 7 s − 1 no polarization transfer is observed. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) severely lowers the life quality by progressively destructing joint functions and eventually causing permanent disability, representing a pressing public health concern. The pathogenesis of RA includes the excessive production of proinflammatory cytokines and harmful oxygen-derived free radicals, such as nitric oxide (NO), which constitute vital targets for precise diagnosis and effective treatment of RA. In this study, we introduce an advanced nanoagent that integrates the RA microenvironment-activatable photoacoustic (PA) imaging with multitarget synergistic treatment for RA. A highly sensitive organic probe with NO-tunable energy transformation and molecular geometry is developed, which enables strong near-infrared absorption with a turn-on PA signal, and the active intramolecular motion could further boost PA conversion. The probe is coassembled with an inflammation-responsive prodrug to construct the theranostic nanoagent, on which a macrophage-derived cell membrane with natural tropism to the inflammatory sites is camouflaged to improve the targeting ability to inflamed joints. The nanoagent could not only sensitively detect RA and differentiate the severity but also efficiently alleviate RA symptoms and improve joint function. The combination of activatable probe-mediated NO scavenging and on-demand activation of anti-inflammatory prodrug significantly inhibits the proinflammatory factors and promotes macrophage repolarization from M1 to M2 phenotype. This meticulously designed nanoagent ingeniously integrates RA-specific PA molecular imaging with synergistic multitarget therapy, rendering tremendous promise for precise intervention of RA-related diseases.

Molecular motion in crystals often suffer from severe limitations on their dynamic processes, and has received an extraordinary attention as artificial molecule motors and potential molecular dielectric materials. To investigated the relationship between the molecules motion in crystals and dielectric properties. Here, two hybrid crystals [1,3-bis(1-mim)C 3 ] 2 [Pb 4 Cl 12 ] (1) and [1,3-bis(1-mim)C 3 ][Pb 2 Cl 6 ] (2) (1,3-bis(1-mim)C 3 = 1,3-bis(1-methylimidazolium)propane), which undergoes interesting dielectric relaxation and molecules motion were reported. Temperature-dependent single crystal structure shows the trans-cis transition of the carbon atoms and twisted rotation of the imidazolium ring were observed for 2. For 1 , there exists thermal activating rapid motion for cation. Two compounds exhibit dielectric relaxation.The dielectric constant of 2 are much larger than 1 at the same frequency, which can be ascribed to the reorientational dynamics of guest water molecules and twisted rotation of the cation. Image 1 • The obvious molecular motion was observed for 2. • 1 exhibits a very low dielectric constant. • Two compounds show dielectric relaxation. [ABSTRACT FROM AUTHOR]

Highlights • The metalloprotease is composed by three conserved domains. • The Mn+2 and Ca+2 ions partially protect the enzyme from thermal denaturation. • A dynamical model for its active and inactive conformations has been proposed. Abstract The molecular dynamics of the Pseudomonas fluorescens 07A metalloprotease in the presence of structural Ca2+ and Mn2+ ions was evaluated. Seven Ca2+ ions are primarily bound to the C-terminus, while a divalent cation is located at the catalytic site, acting as a cofactor. The observed enzyme's experimental activity suggests that Mn2+ could compete for the active site of the enzyme with Ca2+, Zn2+ or other divalent cations, thus providing greater catalytic power to the enzyme. Our molecular dynamics simulations suggest that these ions partially protect the enzyme's structure from thermal denaturation. Moreover, our simulations have shown a collective movement of opening-closing of the active-site in simulations with structural Ca2+ and Mn2+ ions bound, leading to a proposal of a dynamical model of P. fluorescens 07A metalloprotease active and inactive conformations. These findings can support the development of measures to control the activity of P. fluorescens and other spoilage microorganism proteases. [ABSTRACT FROM AUTHOR]

The development of molecular machines requires new building blocks which are easy to characterize and visualize to realize a complexity comparable to their natural counterparts such as biological enzymes. Furthermore, with the desire to build functional nanobots capable of navigating living organisms, it is necessary that the building blocks show mobility even in the solid state. Herein we report a system which is emissive in the amorphous state but is non‐fluorescent in the crystalline state due to the formation of extensive π‐π interactions. This dual nature could be exploited for easy visualization of its solid‐state molecular rearrangement. The emission of the amorphous film was quenched as the molecules spontaneously formed π‐π interactions even in the solid state. Scratching the non‐emissive film destroyed the interactions and restored the emission of the film. The emission quickly disappeared with an average lifetime of 20 s as the compound reformed the π‐network even at room temperature. Beacons lit by molecular motion: Intermolecular forces drive the formation of π‐π interactions even in the solid state. Shear forces/scratching disrupt the interactions, turning on emission. The quenched π‐π‐interactions quickly reform even in a film, allowing the visualization of the molecular motions. Theoretical calculations show that the formation of π‐interactions is highly favorable and driving this motion. [ABSTRACT FROM AUTHOR]

The effect of stearic acid-coated nano calcium carbonate (NCC) on transitions and chain mobility of poly(lactic acid) (PLA) was investigated. Dispersion state of NCC in polymeric matrix was explored using scanning electron microscopy and surface tension component measurements. Trends of PLA transitional phenomena were investigated using the results of dynamical mechanical analysis (DMA) and differential scanning calorimetry (DSC) in the nanocomposite systems based on PLA and NCC. In addition, two types of crystal structures and decreasing the glass transition temperature were distinguished using temperature-modulated DSC (TMDSC). Higher melting points of polymer crystals were found in TMDSC experiments due to low and dynamic heating rate compared to the conventional DSC. Dynamics of polymer chains, affected by NCC, were quantified using cooperativity length, ξ α, and the number of relaxing structural units, Nα, in the glass transition region. NCC particles hindered the cooperative motion of polymer chains at glass transitions and crystallization in TMDSC measurements, whereas the DMA results indicated that NCC particles may act as lubricant and simplified chain mobility. [ABSTRACT FROM AUTHOR]

The precise operation of molecular motion for constructing complicated mechanically interlocked molecules has received considerable attention and is still an energetic field of supramolecular chemistry. Herein, we reported the construction of two tris[2]pseudorotaxanes metallacycles with acid–base controllable molecular motion through self-sorting strategy and host–guest interaction. Firstly, two hexagonal Pt(II) metallacycles M1 and M2 decorated with different host–guest recognition sites have been constructed via coordination-driven self-assembly strategy. The binding of metallacycles M1 and M2 with dibenzo-24-crown-8 (DB24C8) to form tris[2]pseudorotaxanes complexes TPRM1 and TPRM2 have been investigated. Furthermore, by taking advantage of the strong binding affinity between the protonated metallacycle M2 and DB24C8, the addition of trifluoroacetic acid (TFA) as a stimulus successfully induces an acid-activated motion switching of DB24C8 between the discrete metallacycles M1 and M2. This research not only affords a highly efficient way to construct stimuli-responsive smart supramolecular systems but also offers prospects for precisely control multicomponent cooperative motion.

Cellulose gel(CG)/poly (ε-caprolactone)(PCL) composites showed extraordinary mechanical properties compared with pure PCL. The tensile maintained quite good even at temperature 40 °C higher than the melting point of PCL. CG/PCL composite was prepared by in-situ ring-opening polymerization. The structure of CG/PCL composites was characterized by XRD, DCS and solid-state NMR. The mass ratio of CG to PCL of composites was measured by quantitative solid-state 13 C-CP/MAS NMR. The mass ratio of the grafted chains to free chains of PCL in the composites was also obtained. By solid-state1 H-MAS NMR, the average molecular weight of PCL in the composites was measured. To understand the reinforcement mechanism of the CG/PCL composite, molecular motion of the composites at different temperatures was also studied. Solid-state 1 H-MAS NMR spectra showed that the full width at half maximum of the composites was significantly wilder than that of pure PCL, indicating that there was a strong dipole-dipole interaction between CG and PCL. The relationship between spin-spin relaxation time (T2) and temperature showed quite different trends for pure PCL and PCL in the composites. T2 of pure PCL showed a sudden increase when temperature increased to near melting point, while for PCL in the composite, the change was not so sharp. Results showed that the molecular motion of PCL chain was restricted by CG, which made the substantial increase of the thermo stability and high-temperature strength. From the other side, the molecular chains of CG were also influenced by PCL, leading to slight increase of its molecular motion, which made the composite much more flexible than pure CG. [ABSTRACT FROM AUTHOR]

A novel fluorescent switchable [2]rotaxane NIR4 composed of two different molecular stations and rotaxane arms terminated with far-red boron-dipyrromethene (BODIPY) fluorophores and its derivatives were synthesized by CuAAC click chemistry. The molecular shuttling motion of mechanically interlocked molecules (MIMs) could be addressed by the fluorescence signal transduction via distance dependent photo-induced electron transfer process of [2]rotaxane NIR4 triggered by external chemical stimuli of acid/base. Moreover, the flexible arms of triazolium moiety in [2]rotaxane NIR4 and its axle NIR2 exhibited impressive selectivity and sensitivity toward complementary anionic analyte (H 2 PO 4 − ), where the specific mechanical molecular motion was supported by quantum mechanical calculations. The development of [2]rotaxane NIR4 with a high level of structural complexity can be utilized for novel dual sensory detections of acid-base and dihydrogen phosphate (H 2 PO 4 − ) anion. Importantly, the host of NIR2 and [2]rotaxane NIR4 could be applied for the vitro imaging and clarify the distribution of H 2 PO 4 − at subcellular levels. [ABSTRACT FROM AUTHOR]