Functionalized Electrode Additive for Simultaneously Reinforcing Chemo-Mechanical Properties of Millimeter-Thick Dry-Electrode for High-Energy All-Solid-State Batteries

Voids are widely disseminated in a powder when mixed, and hence the typical dry-electrode preparation method yields a sparse dry-electrode because the external pressure applied to the surface of the mixed powder is not evenly distributed. Consequently, particle cracking and void remnants appear in the electrode after calendaring. This study introduces a practically applicable bi-functionalized electrode additive to simultaneously reinforce the chemo-mechanical properties of millimeter-thick dry electrodes. The agyrodite Li₆PS₅Cl solid electrolyte and lithium difluorophosphate (LiPO₂F₂) additive have different sizes, as demonstrated by their densification from their elaborate bimodal structure, which is densely packed. Because the additive is filled into the interparticle voids in the electrode sheet during electrode fabrication, a decrease in electrode cracking after calendaring is possible because of the uniform distribution of external pressure. Hence, a thin, highly ionic/electronic-conductive electrode can be constructed by the addition of LiPO₂F₂ additive. Furthermore, during the formation, the active material surface-contacted LiPO₂F₂ promptly produces a surface layer comprising LiF and Li_xPF_y. Thus, the addition of LiPO₂F₂ further reduces the degradation of Li₆PS₅Cl solid electrolytes. As a result, the LiPO₂F₂ additive simultaneously improves the electrochemical and physicochemical properties of millimeter-thick dry-electrodes for high-energy all-solid-state battery systems.     

Flexible docking allowing induced fit in proteins: Insights from an open to closed conformational isomers

Here we dock a ligand onto a receptor surface allowing hinge-bending domain/substructural movements. Our approach mimics and manifests induced fit in molecular recognition. All angular rotations are allowed on the one hand, while a conformational space search is avoided on the other. Rather than dock each of the molecular parts separately with subsequent reconstruction of the consistently docked molecules, all parts are docked simultaneously while still utilizing the position of the hinge from the start. Like pliers closing on a screw, the receptor automatically closes on its ligand in the best surface-matching way. Movements are allowed either in the ligand or in the larger receptor, hence reproducing induced molecular fit. Hinge bending movements are frequently observed when molecules associate. There are numerous examples of open versus closed conformations taking place upon binding. Such movements are observed when the substrate binds to its respective enzyme. In particular, such movements are of interest in allosteric enzymes. The movements can involve entire domains, subdomains, loops, (other) secondary structure elements, or between any groups of atoms connected by flexible joints. We have implemented the hinges at points and at bonds. By allowing 3-dimensional (3-D) rotation at the hinge, several rotations about (consecutive or nearby) bonds are implicitly taken into account. Alternatively, if required, the point rotation can be restricted to bond rotation. Here we illustrate this hinge-bending docking approach and the insight into flexibility it provides on a complex of the calmodulin with its M13 ligand, positioning the hinges either in the ligand or in the larger receptor. This automated and efficient method is adapted from computer vision and robotics. It enables utilizing entire molecular surfaces rather than focusing a priori on active sites. Hence, allows attaining the overall optimally matching surfaces, the extent and type of motions which are involved. Here we do not treat the conformational flexibility of side-chains or of very small pieces of the molecules. Therefore, currently available methods addressing these issues and the method presented here, are complementary to each other, expanding the repertoire of computational docking tools foreseen to aid in studies of recognition, conformational flexibility and drug design. Proteins 32:159–174, 1998. © 1998 Wiley-Liss, Inc.     

Cyclic oligomer design with de novo αβ‐proteins

We have previously shown that monomeric globular αβ‐proteins can be designed de novo with considerable control over topology, size, and shape. In this paper, we investigate the design of cyclic homo‐oligomers from these starting points. We experimented with both keeping the original monomer backbones fixed during the cyclic docking and design process, and allowing the backbone of the monomer to conform to that of adjacent subunits in the homo‐oligomer. The latter flexible backbone protocol generated designs with shape complementarity approaching that of native homo‐oligomers, but experimental characterization showed that the fixed backbone designs were more stable and less aggregation prone. Designed C2 oligomers with β‐strand backbone interactions were structurally confirmed through x‐ray crystallography and small‐angle X‐ray scattering (SAXS). In contrast, C3‐C5 designed homo‐oligomers with primarily nonpolar residues at interfaces all formed a range of oligomeric states. Taken together, our results suggest that for homo‐oligomers formed from globular building blocks, improved structural specificity will be better achieved using monomers with increased shape complementarity and with more polar interfaces.     

Investigating the structural dynamics of the PIEZO1 channel activation and inactivation by coarse‐grained modeling

The PIEZO channels, a family of mechanosensitive channels in vertebrates, feature a fast activation by mechanical stimuli (eg, membrane tension) followed by a slower inactivation. Although a medium‐resolution structure of the trimeric form of PIEZO1 was solved by cryo‐electron microscopy (cryo‐EM), key structural changes responsible for the channel activation and inactivation are still unknown. Toward decrypting the structural mechanism of the PIEZO1 activation and inactivation, we performed systematic coarse‐grained modeling using an elastic network model and related modeling/analysis tools (ie, normal mode analysis, flexibility and hotspot analysis, correlation analysis, and cryo‐EM‐based hybrid modeling and flexible fitting). We identified four key motional modes that may drive the tension‐induced activation and inactivation, with fast and slow relaxation time, respectively. These modes allosterically couple the lateral and vertical motions of the peripheral domains to the opening and closing of the intra‐cellular vestibule, enabling external mechanical forces to trigger, and regulate the activation/inactivation transitions. We also calculated domain‐specific flexibility profiles, and predicted hotspot residues at key domain‐domain interfaces and hinges. Our results offer unprecedented structural and dynamic information, which is consistent with the literature on mutational and functional studies of the PIEZO channels, and will guide future studies of this important family of mechanosensitive channels.     

A salt-bridge switch in the molecular recognition between RS receptor and RGD ligand from the ABEEM σπ molecular dynamics simulations

Abstract

How the receptor and ligand recognise each other is a challenging subject in explaining the mechanism of recognition at the molecular level. As a starting point, here, a synthesised RS receptor and its RGD ligand were investigated as a proper model to simulate their recognition process in terms of ABEEMσπ/MM polarisable force field. It is found that a switch of forming up a salt bridge in the ligand triggers the recognition of the receptor and ligand. Through the salt-bridge switch that undergoes several cycles from on-state with parallel hydrogen bonds to off-state with bifurcated hydrogen bonds, the active site of ligand can flex easily to interact with the active site of the receptor. In addition, the water molecules form a decisive bridge connecting the active sites of the bound system. The salt-bridge switch and water-mediated movement are cooperative as the important factors for the receptor-ligand recognition. In addition, the properties, such as binding free energy, conformational flexibility and solvent accessible surface area have been calculated to provide adequate evidence for the whole recognition process. According to the simulation, a detailed mechanism was derived involving diffusion, a switch triggered cooperative water-mediated movement, and conformational folding, for the flexible recognition.     

Large Voltage Generation of Flexible Thermoelectric Nanocrystal Thin Films by Finger Contact

This paper demonstrates that thermal energy radiated from a human finger can be converted efficiently into electricity by a nanocrystal (NC) thin film that substantially suppresses thermal conduction, but still allows electric conduction. The converting efficiencies of the chalcogenide NC thin films with dimensions 40 µm × 20 µm × 20 nm, prepared on flexible substrates by a solution process, are maximized by adjusting the NC size. A Seebeck coefficient of S = 1829 µV K^?1, and a dimensionless thermoelectric figure‐of‐merit, ZT = 0.68 are achieved at ambient temperature for p‐ and n‐type NC thin films, respectively. A thermoelectric array consisting of p‐ and n‐type NC thin films generates a voltage of 645 mV for a temperature gradient of 10 K. Furthermore, the donut‐shaped pn array can generate a voltage of 170 mV from the heat supplied by an individual's finger.     

Multiscale Morphological and Electrical Characterization of Charge Transport Limitations to the Power Performance of Positive Electrode Blends for Lithium‐Ion Batteries

In this work, exhaustive characterizations of 3D geometries of LiNi_1/3Mn_1/3Co_1/3O₂ (NMC), LiFePO₄ (LFP), and NMC/LFP blended electrodes are undertaken for rational interpretation of their measured electrical properties and electrochemical performance. X‐ray tomography and focused ion beam in combination with scanning electron microscopy tomography are used for a multiscale analysis of electrodes 3D geometries. Their multiscale electrical properties are measured by using broadband dielectric spectroscopy. Finally, discharge rate performance are measured and analyzed by simple, yet efficient methods. It allows us to discriminate between electronic and ionic wirings as the performance limiting factors, depending on the discharge rate. This approach is a unique exhaustive analysis of the experimental relationships between the electrochemical behavior, the transport properties within the electrode, and its 3D geometry.     

Hierarchically Structured 3D Integrated Electrodes by Galvanic Replacement Reaction for Highly Efficient Water Splitting

A NiFe‐based integrated electrode is fabricated by the spontaneous galvanic replacement reaction on an iron foam. Driven by the different electrochemical potentials between Ni and Fe, the dissolution of surface Fe occurs with electroless plating of Ni on iron foam with no need to access instrumentation and input energy. A facile cyclic voltammetry treatment is subsequently applied to convert the metallic NiFe to NiFeO_x . A series of analytical methods indicates formation of a NiFeO_x film of nanosheets on the iron foam surface. This hierarchically structured three dimensional electrode displays high activity and durability against water oxidation. In 1 m KOH, a current density of 1000 mA cm^?2 is achieved at an overpotential of only 300 mV. This method is readily extended to fabricate CoFe or NiCoFe‐based integrated electrodes for water oxidation. Phosphorization of the bimetallic oxide (NiFeO_x ) generates the bimetallic phosphide (NiFe‐P), which can act as an excellent electrocatalyst for hydrogen production in 1 m KOH. An alkaline electrolyzer is constructed using NiFeO_x and NiFe‐P coated iron foams as anode and cathode, which can realize overall water splitting with a current density of 100 mA cm^?2 at an overpotential of 630 mV.