Substitution Sites Research Articles

AAV vector transduction restriction and attenuated toxicity in hESCs via a rationally designed inverted terminal repeat.

Adeno-associated virus (AAV) inverted terminal repeats (ITRs) induce p53-dependent apoptosis in human embryonic stem cells (hESCs). To interrogate this phenomenon, a synthetic ITR (SynITR), harboring substitutions in putative p53 binding sites was generated and evaluated for vector production and gene delivery. Replication of SynITR flanked transgenic genome was similar compared to wildtype (wt)ITR, with a modest increase in vector titers. Packaged in the AAV2 capsid, wtITR and SynITR vectors demonstrated similar transduction efficiencies of human cells without toxicity. Following AAV2-wtITR vector infection of hESCs, rapid apoptosis was observed as reported. In contrast, infection by AAV2 vectors packaged with SynITRs attenuated the wtITR-induced hESC toxicity. While hESC particle entry and the abundance of double stranded circular episomes was similar for the ITR contexts, reporter expression was inhibited from transduced SynITR genomes. Mechanistically, infection of hESCs induced γH2AX in an ITR-independent manner, however, canonical activation of p53α was uncoupled using AAV-SynITR. Further investigations in hESCs revealed additional novel findings: (i) p53β is uniquely and constitutively activeand (ii) AAV vector infection, independent of the ITR sequence, induces activation of p53ψ. The data herein reveal an ITR-dependent AAV vector transduction restriction specific to hESCs and manipulation of the DNA damage response via ITR engineering.

Modulating Electronic Spin State of Perovskite Fluoride by Ni─F─Mn Bond Activating the Dynamic Site of Oxygen Reduction Reaction.

Establishing the relationship between catalytic performance and material structure is crucial for developing design principles for highly active catalysts. Herein, a type of perovskite fluoride, NH4MnF3, which owns strong-field coordination including fluorine and ammonia, is in situ grown on carbon nanotubes (CNTs) and used as a model structure to study and improve the intrinsic catalytic activity through heteroatom doping strategies. This approach optimizes spin-dependent orbital interactions to alter the charge transfer between the catalyst and reactants. As a result, the oxygen reduction reaction (ORR) activity of NH4MnF3 on CNTs is significantly enhanced by partial substitution of Mn sites with Ni, such as a half-wave potential (E1/2) of 0.86V and a limiting current density of 5.26mA cm-2, which are comparable to those of the commercial Pt/C catalysts. Experimental and theoretical calculations reveal that the introduction of Ni promotes lattice distortion, adjusts the electronic states of the active Mn centers, facilitates the transition from low-spin to intermediate-spin states, and shifts the d-band center closer to the Fermi level. This study establishes a novel approach for designing high-performance perovskite-based fluoride electrocatalysts by modulating spin states.

Unprecedented Site Preference of Sn in the Structure of CoSn-Type NiIn1-xSnx (x < 0.7).

A series of compositions NiIn1-xSnx (x = 0-1) were synthesized by conventional high-temperature synthesis, and as-synthesized samples were checked by powder X-ray diffraction experiments. NiIn1-xSnx (x < 0.7) mainly forms the ternary variant of the CoSn-type structure (P6/mmm), whereas, x = 0.7-0.9, NiIn1-xSnx forms predominantly an orthorhombic (Pnma) phase. To resolve the accurate crystal structure of hexagonal NiIn1-xSnx, a combination of single-crystal X-ray diffraction and neutron powder diffraction techniques is employed. It is revealed that in the crystal structure of NiIn1-xSnx (x < 0.7), the Sn gradually substitutes one of the two In sites present in the NiIn (CoSn-type) and forms the pseudobinary NiIn1-xSnx (x < 0.7). These experimental findings on the specific site substitution are supplemented by first-principles density functional theory (DFT) calculations. Mulliken's and Löwdin's population and Bader charge analyses further support the unexpected substitution of Sn for one In site in the structure of hexagonal NiIn1-xSnx. The structure can be viewed as an alternating arrangement of two flat atomic layers in the [001]: Kagomé layer of Ni atoms with indium at the center of the hexagons and honeycomb nets of In/Sn. Density of state (DOS) calculations, crystal orbital Hamilton population (COHP) calculations, and crystal orbital bond index (COBI) calculations further elucidate the stability and bonding scenario in the hexagonal phases. Interestingly, gradual Sn inclusion into the CoSn-type NiIn downshifts the 3d band center from the Fermi level that could influence the catalytic performance as well as many intriguing properties. These findings not only contribute to the fundamental understanding of atomic ordering between neighboring elements in NiIn1-xSnx but also pave the way for designing fascinating physical and chemical properties.

Genetic characteristics of influenza A and B viruses circulating in Russia in 2019–2023

Relevance. Influenza viruses have a high potential for genetic change. These viruses are monitored annually around the world, including Russia, to determine the dominant genetic groups and select the strains to be included in influenza vaccines. Objectives of the study include: analysis of influenza virus circulation in Russia in 2019–2023, phylogenetic and molecular analysis of hemagglutinin (HA) sequences of influenza viruses, detection of mutations associated with drug resistance to neuraminidase (NA) inhibitors and M2-protein (M2) ion channel inhibitors. Materials and methods. Biological samples containing RNA of influenza viruses were studied: 410 A(H1N1)pdm09, 147 A(H3N2) and 167 B(Victoria). Sequencing of the HA, NA, M fragments was performed on the 3500xL Genetic Analyzer (Applied Biosytems). Data processing and analysis were carried out using DNASTAR, Nextclade, FluSurver and BioNumerics v.6.6 software. Results. Influenza A(H1N1)pdm09, A(H3N2), B(Victoria) viruses circulating in 2019-2023 were investigated. The highest variability of HA was observed in A(H3N2) viruses. All influenza A(H1N1)pdm09 viruses in the 2022–2023 season had a previously unknown mutation E224A in HA, which increases its affinity for α-2,3 sialic acids — receptors localized in the human lungs, to which the virus binds via HA. 2 and 3% of influenza A(H1N1)pdm09 viruses in 2019–2020 and 2022–2023, respectively, had the D222N mutation in the receptor-binding site of HA, which is associated with more severe disease. The oseltamivir and zanamivir resistance mutation H275Y in NA was detected in 2.3% of influenza A(H1N1)pdm09 viruses in 2022–2023. No oseltamivir and zanamivir resistance mutations in NA were detected in all tested influenza A(H3N2) and B viruses. Sequencing data revealed a mutation of adamantane resistance S31N in M2 in all studied influenza viruses A(H1N1)pdm09 and A(H3N2). Conclusions. The detection of amino acid substitutions in HA antigenic sites and resistance mutations in NA and M2 confirms the evolution of influenza viruses and the necessity for continuous genetic surveillance. The vast majority of currently circulating viruses remain sensitive to NA inhibitors.

Recent Development in Hydantoins, Thiohydantoins, and Selenohydantoins as Anticancer Agents: Structure-activity Relationship and Design Strategies.

Hydantoin, a five-membered heterocyclic scaffold, is regarded as a crucial scaffold in medicinal chemistry. Hydantoins have been useful in synthesizing medicines like nilutamide, enzalutamide, and apalutamide. Thiohydantoin and selenohydantoin have been discovered as two separate types of hydantoin. There are two hydrogen bond donors, two hydrogen bond acceptors, and four substitution sites. These characteristics have led to the design, synthesis, and expansion of hydantoin derivatives' biological and pharmacological effects against numerous types of malignancies. This study reviews the recent contributions of hydantoin and its isosteric variants to medicinal chemistry. To emphasize their significance, certain significant compounds based on hydantoins and their structure activity relationships (SAR) are briefly discussed. We thoroughly analyzed each scaffolds' structural characteristics and SAR, and these scaffolds may one day show potential anticancer activities.

AIE-Active Circularly Polarized Thermally Activated Delayed Fluorescence Emitters for Stable Solution-Processed Circularly Polarized Electroluminescence.

Circularly polarized organic light-emitting diodes (CP-OLEDs) have significant promise for naked-eye 3D displays. However, most devices are fabricated using vacuum deposition technology, and development of efficient solution-processed CP-OLEDs, particularly those exhibiting low efficiency roll-off, remains a formidable challenge. This research successfully designed and synthesized two pairs of thermally activated delayed fluorescence (TADF) enantiomers through isomer engineering, namely (R/S)-N-5-TPA and (R/S)-N-4-TPA, which features fifth and fourth substitution sites of phthalimide (acceptor) by tri-phenylamine (donor), respectively. Both molecules displayed aggregation-induced emission (AIE) properties. Notably, the CP-OLED devices, fabricated by solution-process, exhibited vivid blue-green and green emission with the maximum current efficiency of 7.4 and 29.6 cd A-1, the external quantum efficiency of 2.7 % and 10.2 %, and the low efficiency roll-off of 3.7 % and 16.7 %. Moreover, these devices demonstrated CP-EL signals with gEL values of +6.61×10-4 /-6.84×10-4 and +1.13×10-3/-1.25×10-3, respectively.

Exploring the Impact of Structural Modifications of Phenothiazine-Based Novel Compounds for Organic Solar Cells: DFT Investigations.

This paper explores a novel group of D-π-A configurations that has been specifically created for organic solar cell applications. In these material compounds, the phenothiazine, the furan, and two derivatives of the thienyl-fused IC group act as the donor, the π-conjugated spacer, and the end-group acceptors, respectively. We assess the impact of substituents by introducing bromine atoms at two potential substitution sites on each end-group acceptor (EG1 and EG2). With the donor and π-bridge held constant, we have employed density functional theory and time-dependent DFT simulations to explore the photophysical and optoelectronic properties of tailored compounds (M1-M6). We have demonstrated how structural modifications influence the optoelectronic properties of materials for organic solar cells. Moreover, all proposed compounds exhibit a greater Voc exceeding 1.5 V, a suitable HOMO-LUMO energy gap (2.14-2.30 eV), and higher dipole moments (9.23-10.90 D). Various decisive key factors that are crucial for exploring the properties of tailored compounds-frontier molecular orbitals, transition density matrix, electrostatic potential, open-circuit voltage, maximum absorption, reduced density gradient, and charge transfer length (Dindex)-were also explored. Our analysis delivers profound insights into the design principles of optimizing the performance of organic solar cell applications based on halogenated material compounds.

Effects of benzoheterocyclic annelation on the s-indacene core: a computational analysis.

Aromaticity and antiaromaticity are pivotal concepts in chemistry, with significant implications for molecular properties and reactivity. In particular, thanks to their increased conductivity and small HOMO-LUMO energy gaps, antiaromatic molecules are promising for use in organic electronics. The inherent instability of such molecules is often addressed by carbocyclic fusion, which also reduces the antiaromaticity of the core structure. Herein, we have employed a computational approach to explore the effects of heterocyclic fusion on the s-indacene core, focusing on three main aspects: the impact of the heteroatom, the heterocycle, and extended conjugation. We found that the heteroatoms themselves can substantially modulate antiaromaticity, and that the site of substitution plays a large role in the extent of stabilization afforded. Heterocycle fusion further modulates antiaromaticity, though to a lesser extent than the heteroatom effect. This effect diminishes upon benzannelation, highlighting the complexity of aromatic and antiaromatic interplay. Our findings offer a nuanced understanding of the factors affecting antiaromaticity in s-indacene-based polycyclic systems, providing a conceptual framework for predicting and tuning these properties for applications in organic electronics. This work underscores the importance of both substitution position and heterocyclic fusion in designing stable antiaromatic compounds.

Role of amino acid substitutions on proteolytic stability of histatin 5 in the presence of secreted aspartyl proteases and salivary proteases

AbstractHistatin 5 (Hst5) is a 24‐amino‐acid peptide naturally present in human saliva that has been proposed as a potential antifungal therapeutic. However, Hst5 is susceptible to degradation by secreted aspartyl proteases (Saps) produced by Candida albicans, which could limit its efficacy as a therapeutic. To better understand the role of the lysine residues of Hst5 in proteolysis by C. albicans Saps (Sap1, Sap2, Sap3, Sap5, Sap6, Sap9, and Sap10), we studied variants of Hst5 with substitutions to leucine or arginine at the lysine residues (K5, K11, K13, and K17). Sap5, Sap6, and Sap10 did not degrade Hst5 or the variants. However, we observed degradation of the peptides by Sap1, Sap2, Sap3, and Sap9, and the degradation depended on the site of substitution and the substituent residue. Some modifications, such as K11L and K13L, were particularly susceptible to proteolysis by Sap1, Sap2, Sap3, and Sap9. In contrast, the K17L modification substantially increased the stability and antifungal activity of Hst5 in the presence of Saps. We used mass spectrometry to characterize the proteolysis products, which allowed us to identify fragments likely to have maintained or lost antifungal activity. We also evaluated the proteolytic stability of the Hst5 variants in saliva. Both K17L and K5R showed improved stability; however, the enhancements were modest, suggesting that further engineering is required to achieve significant improvements. Our approach demonstrates the potential of simple, rational substitutions to enhance peptide efficacy and proteolytic stability, providing a promising strategy for improving the properties of antifungal peptides.

Amino Acid Substitutions in the Fusion Protein of Respiratory Syncytial Virus in Fukushima, Japan, During 2008–2023 and Their Effects

Abstract Background Amino acid (AA) substitutions in the fusion (F) protein of respiratory syncytial virus (RSV) and their effects on antibody susceptibility remain unclear. We analyzed AA substitutions in the main neutralizing epitopes of the F protein. Methods We analyzed F protein genes of 236 RSV strains isolated from children hospitalized with RSV infection in Fukushima, Japan (June 2008–February 2023). AA substitutions in antigenic sites II, V, and Ø were detected, and their effects on antibody susceptibility and viral replication were evaluated. Results Site II: The K272M (RSV-A) and the K272E (RSV-B) substitutions in strains from palivizumab-treated children reduced antibody susceptibility. Site V: In RSV-A, &amp;gt;50% of strains isolated since 2022 harbored the V178I substitution; however, this did not change antibody susceptibility. In RSV-B, L172Q/S173L mutant strains became predominant around 2016, leading to reduced antibody susceptibility. Site Ø: No AA substitutions were detected in RSV-A. In RSV-B, the I206M/Q209R mutant strain became predominant around 2018, leading to improved antibody susceptibility and replicative ability. However, none of the substitutions reduced antibody susceptibility. Conclusions The RSV F protein in Fukushima has naturally undergone AA substitutions with corresponding changes in antibody susceptibility, including unique regional patterns. Monitoring substitutions and antibody susceptibility is essential.

Positive Selection Shapes Breast Cancer Tumor Suppressor Genes: Unveiling Insights into BRCA1, BRCA2, and MDC1 Stability.

Worldwide, breast cancer is the leading cause of death in women with cancers. Given this situation, new approaches to treatment are urgently needed. Tumor Suppressor Genes (TSGs) defects play a crucial role in tumor development, and recent studies propose their reactivation as a promising way for clinical intervention in breast cancer. Here, we performed detailed evolutionary analyses of 241 breast cancer TSGs across 25 mammalian genomes, revealing 28 genes under strong positive selection. These genes exhibit elevated molecular pressure in codons corresponding to amino acids located in crucial protein domains and motifs. Notably, one positively selected site in the BRCA1 C-terminal domain is known for its role in DNA damage response, suggesting potential interference with DNA repair mechanisms. Moreover, the substitution of some other sites found in important key motifs, namely two codons in BRCA2 (752 and 939) localized within the phosphoinositide-3-OH-kinase-related and playing a crucial role in the DNA repair and the DNA damage checkpoints. Our findings could be inspirational to foster future recommendations for drug-targeting sites and further illuminate the function of these proteins. Finally, the code developed in our study is delivered in the Automated tool for positive selection (ATPs) ( https://github.com/APS-P/Automated-Tool-for-Positive-Selection-ATPS-/wiki ) to assist the easy reproducibility and support future evolutionary genomics analyses.

Prevalence and molecular characterization of human bocavirus-1 in children and adults with influenza-like illness from Kunming, Southwest China.

Human bocavirus-1 (HBoV-1) has been associated with respiratory infections in both children and adults, often presenting symptoms similar to those of influenza. Understanding the prevalence and molecular characteristics of HBoV-1 in individuals with influenza-like illness (ILI) is essential for enhancing the diagnosis and treatment of respiratory infections in Kunming, Southwest China. Between December 2017 and December 2023, demographic and clinical data, along with respiratory tract specimens from individuals aged 0 to 97 years with ILI, were collected at three sentinel hospitals in Kunming. Each specimen was tested for 18 respiratory viruses, and the positive rates of HBoV-1 across different age groups were analyzed. Amplification of the near-complete HBoV genome was achieved through three overlapping fragments, followed by next-generation sequencing (NGS) and phylogenetic analysis. A total of 20,181 respiratory samples were collected from patients aged 1 month to 97 years presenting with ILI symptoms between December 2017 and December 2023, with HBoV detected in 0.8% of the samples. The prevalence was 1.0% (165/16,406) in children and 0.1% (3/3,775) in adults, with a significantly higher detection rate in pediatric patients (<18 years old) compared to adults (≥18 years old) (P < 0.001). Among the 168 HBoV-positive participants, 165 (98.2%) were children under 18 years, while 3 (1.8%) were adults. Genome-wide phylogenetic analyses indicated that HBoV-1 was the predominant genotype, showing that the HBoV-1 strains circulating in Kunming are closely related to strains from other regions of China and globally. Our findings confirm the prevalence of HBoV-1 in individuals with ILI in Kunming and provide valuable insights into the molecular characteristics of HBoV-1 in this region. Further studies are necessary to explore the clinical implications of HBoV-1 infection and its role in respiratory illnesses.IMPORTANCEViral respiratory infections are a leading cause of morbidity- and mortality-associated influenza-like illness (ILI) cases. It is estimated that there are several billion cases of ILI globally each year. Monitoring data from China in 2023 indicate that there are approximately 17 million cases of ILI nationwide. In the United States, the annual incidence of ILI ranges from 9 to 49 million cases. Human bocavirus-1 (HBoV-1) has been identified as a causative agent of ILI. The global prevalence of HBoV-1 respiratory infections varies from 1% to 56.8%, with the majority of studies focusing on pediatric populations; however, research including a broader age range is limited. Currently, the prevalence of HBoV-1 in the Kunming area is not well characterized, and its molecular features remain inadequately described. This study aims to analyze the prevalence of HBoV-1 among ILI cases in Kunming, encompassing both pediatric and adult patients. We present 107 complete genomic sequences of HBoV-1 strains obtained from three ILI sentinel hospitals in the region. Furthermore, we conducted phylogenetic analysis, homology comparisons, and assessments of nucleotide and amino acid substitution site variations. These findings provide important insights for further investigations into HBoV-1 and its epidemiological significance.

Impact of vascular Ehlers-Danlos Syndrome-associated Gly substitutions on structure, function, and mechanics using bacterial collagen.

Vascular Ehlers-Danlos syndrome (vEDS) arises from mutations in collagen-III, a major structural component of the extracellular matrix (ECM) in vascularized tissues, including blood vessels. Fibrillar collagens form a triple-helix that is characterized by a canonical (Gly-X-Y)n sequence. The substitution of another amino acid for Gly within this conserved repeating sequence is associated with several hereditary connective tissue disorders, including vEDS. The clinical severity of vEDS depends on the identity of the substituted amino acid and its location. In this study, we engineered recombinant bacterial collagen-like proteins (CLPs) with previously reported Gly→X (X=Ser or Arg) vEDS substitutions within the integrin-binding site. Employing a combination of biophysical techniques, enzymatic digestion assays, integrin binding affinity assays, and computational modeling, we assessed the impact of Gly→X substitutions on structure, stability, function, and mechanical properties. While constructs with Ser or Arg substitutions maintained a triple-helix structure, Arg substitution significantly reduced global thermal stability, heightened susceptibility to trypsin digestion, and altered integrin α2-inserted (α2I) domain binding. Molecular dynamics (MD) simulations also demonstrated distinct effects of different Gly substitutions on the triple-helix structure - Arg substitutions induced notable bulging at the substitution site and disrupted interchain hydrogen bonds compared to Ser substitutions. Additionally, steered MD simulations revealed that Arg substitution led to a significant decrease in Young's modulus of the triple-helix. Bacterial CLPs have proved to be a powerful model for studying the underlying mechanisms of vEDS-causing mutations in collagen-III. Serine and arginine substitutions differentially perturb cell-matrix interactions and ECM in a manner consistent with clinical vEDS severity.

Molecular Design of n-Type Organic Semiconductors with Ultralow Electron Reorganization Energies.

Bottom-up design of n-type organic semiconductors with salient electron-transport properties is of fundamental importance. Here, with the aid of density functional theory, we demonstrate that condensing odd-membered carbon rings (5MR/7MR) to small polycyclic aromatic hydrocarbons (PAHs) can endow molecules with ultralow electron reorganization energies (λ < 100 meV). Studying 60 molecules, we find that introducing polycyclic fragments with built-in 5MR and 7MR to linear PAHs at the Cα,β positions or to nonlinear PAHs in D2h symmetry constitutes molecules with λ as low as 65 meV. A joint ACID and NICS analysis proves that the stronger the molecular aromaticity, the lower the λ will be. This is contrary to what has been previously found for p-type molecules. Furthermore, we propose "acupoints" on molecules for N-doping and cyanation, which can be used to precisely locate the substitution sites to reduce the LUMO energies (in favor of electron injection and air stability) of low-λ molecules while it does not elevate λ. These findings would help to reduce the synthetic blindness/cost and contribute to the bottom-up design of n-type small-molecule organic semiconductors.

Heteroatom Effect on Site-Selective Oxygen-Sulfur Substitution Reactions of Keggin-Type Polyoxotungstates.

Sulfur, a group 16 element, can substitute the oxygen sites of metal oxides, potentially providing them with unique properties and enabling new applications. Polyoxometalates (POMs) are anionic metal oxide clusters with wide structural diversity owing to arbitrary selection of their constituting metal atoms. However, substitution of the oxygen sites of POMs with sulfur atoms has been rarely explored. Recently, we reacted a Keggin-type POM [XW12O40]4- (IX; X = Si and Ge) with a sulfurizing reagent (Lawesson's reagent), synthesizing Keggin-type polyoxothiometalates (POTMs) [XW12O28S12]4- (IIX, X = Si and Ge) in which all 12 terminal oxygen atoms of IX were site-selectively substituted with sulfur atoms. Although the selected heteroatoms (X) and anion charges substantially influence the properties and reactivities of POMs, oxygen-sulfur substitution of Keggin-type POMs with other heteroatoms and anion charges has not been attempted. Herein, we report the oxygen-sulfur substitution reaction of Keggin-type POMs [XW12O40]n- (IX; X = Al, Si, and P; n = 5, 4, and 3, respectively) with various heteroatoms, yielding the corresponding Keggin-type POTMs [XW12O28S12]n- (IIX). The oxygen-sulfur substitution reaction depended on the heteroatom: POMs with higher anion charges reacted more strongly with the sulfurizing reagents. We also investigated the reaction mechanism of POMs and sulfurizing reagents.

Optimization of Hydride–Ion Conductivity of Perovskite–Type Structure in SrLiH3–CaLiH3–NaLiH2 Quasi–Ternary System

Introduction Solid electrolytes with high ionic conductivities are essential for the development of all–solid–state batteries. Our prior research has identified perovskite–type AELiH3 (AE = Ca, Sr, Ba) as an emerging hydride–ion conductor.[1] Using the nudged elastic bandmethod revealed that the smaller A–site cation offers the lower migration energy. Experimentally, the synthesis of AE 1–x Na x LiH3–x was attempted, and a similar trend in conductivity was observed. However, it was found that CaLiH3 could not be synthesized, possibly due to an unfavorable tolerance factor (t = 0.83) for the cubic perovskite structure. In this study, we explored the compositional space in the SrLiH3–CaLiH3–NaLiH2 quasi–ternary diagram to investigate the formation range of the perovskite-type structure. Inspired by the NEB calculation results noted above, the A-site cations of the SrLiH3–NaLiH2 quasi-binary system were substituted by smaller Ca2+ ions, aiming to reduce the migration energy. Furthermore, the association energy between dopants and hydrogen vacancies, which is a constituent of the activation energy in addition to the migration energy, was calculated through DFT calculations. The relationship between the composition, the activation energy, and the ionic conductivity was investigated to establish material designing principle for perovskite-type hydride-ion conductors. Methodology The synthesis was carried out via the mechanochemical milling at 600 rpm for 12 h. The obtained samples were subjected to X–ray diffraction (XRD) measurement to identify the constituent phases. Synchrotron XRD (BL02, SPring–8, Japan), and neutron powder diffraction (NPD) data (BL09 SPICA, J–PARC, Japan) were obtained. The crystal structure was refined by Rietveld analysis using the Z–Rietveld software. The ionic conductivities of the uniaxially compressed powder samples were measured by alternating current impedance. Density functional theory calculations were performed using the projector-augmented wave method and PBEsol functional as implemented in the VASP code. Results and discussion As the first step, we examined the synthesis of Sr1–x Ca x LiH3 solid solutions. In the range of 0 ≦ x≦ 0.45, the single-phase of cubic perovskite-type structure were obtained. For x ≧ 0.5, secondary phases were detected in XRD patterns, suggesting the solubility limit is x ≈ 0.45. The ionic conductivity enhanced upon increasing the Ca amount, and reached the maximum ionic conductivity, σ 100 ºC = 1.1 × 10–6 S cm–1, for x = 0.5. The activation energy decreased upon Ca-substitution, and reached minimum of 47.2 kJ mol–1 for x= 0.45. These results suggest the activation energy can be mitigated by employing a smaller A-site cation, in accordance with NEB calculation results. Next, perovskite-type hydride-ion conductors within the SrLiH3–CaLiH3–NaLiH2 quasi-ternary system were explored. The figure shows heat map of the ionic conductivities in the SrLiH3–CaLiH3–NaLiH2 quasi-ternary system. The composition of Sr0.75Ca0.1Na0.15LiH2.85 exhibited a maximum ionic conductivity of 1.2 × 10–4 S cm–1 at 100ºC, and Sr0.825Ca0.025Na0.15LiH2.85exhibited a minimal activation energy of 41.8 kJ mol–1, superior over the previously reported hydride-ion conductor Sr0.925Na0.075LiH2.925 (6.4 × 10–5 S cm–1, 46.3 kJ mol–1) [1]. Structural refinement using NPD data of Sr0.7Ca0.1Na0.2LiH2.8confirmed a larger atomic displacement parameter (0.0277) of hydrogen than that of Sr0.8Na0.2LiH2.8 (0.0231(3)), revealing that the A–site substitution by Ca offer more flatten energy landscape of hydrogen in terms of the average structure. In contrast, more substitution by Ca did not provide enhancement of the ionic conductivity. The association energy between the dopant (Na) and a hydrogen–vacancy in AE 63Na1Li64H191 supercell (AE = Ca, Sr, Ba) was calculated to be 19, 14, and 22 kJ mol–1, respectively. The association energy in CaLiH3 was higher than that of SrLiH3, in other words, the local trapping of hydrogen–vacancy by Na is more prominent for CaLiH3. These results suggest the trade-off between the migration energy and the association energy in Sr1–x Ca x Na y LiH3–y . The optimal balance between the migration energy and association energy was achieved with small amounts of Ca (y = 0.025 ~ 0.1), leading to reduced activation energy and enhanced ionic conductivity compared to the previously reported perovskite–type hydride–ion conductors.

(Invited) Enhancing Performance and Moisture Resistance of Solid Electrolyte in Sulfide-Based All-Solid-State Batteries via Oxygen Integration

Issues related to explosions and energy density constraints are presented by lithium-ion batteries (LIBs) employing organic electrolytes.1 The pursuit of overcoming these challenges has brought all-solid-state batteries (ASSBs), representing the next generation of batteries, to prominence as a viable solution. The interest has been directed towards sulfide-based solid electrolytes (SEs), recognized as a crucial component in ASSBs due to their elevated ionic conductivity. Nevertheless, challenges are encountered, encompassing the generation of hazardous hydrogen sulfide (H2S) attributed to the sulfide electrolytes' diminished chemical stability in the presence of moisture, which results in the degradation of cells.2 This necessitates the production of batteries in an environment devoid of reactive elements, thus imposing a hurdle for mass production. To address this issue, two strategies have been delineated: i) the integration of metal oxides such as Fe2O3, ZnO, and zeolite for the sequestration of H2S produced through hydrolysis; ii) the enhancement of SE's stability through doping with Bi, Sn, and Sb in alignment with the theory of hard and soft acids and bases (HSAB), or through replacement with oxides like Li2O and P2O5. The suppression of H2S generation might contribute to prolonged degradation of cells, as it entails the capture of H2S, a breakdown product of SEs. In contrast, the reinforcement of SE structures via the integration of oxygen derivatives is posited to provide the benefit of precluding the generation of H2S while preserving cell efficiency. Despite the notable influence of oxygen inclusion, the elucidation of its impact, anchored in dependable cell functionality and underlying mechanisms, has yet to be fully clarified.3,4 Thus, delving into the comprehension of structural reinforcement mechanisms facilitated by oxygen substitution and their implications is deemed of considerable importance for addressing the intrinsic challenges in SEs.In this study, a novel argyrodite composition incorporating a specified quantity of oxygen has been introduced to simultaneously augment its resistance to moisture and enhance its electrochemical performance without detracting from either attribute. The advantageous effects of oxygen substitution on structural reinforcement, resistance to moisture, and battery properties are delineated. The augmentation of the cathode/SE interface stability through oxygen substitution has been corroborated employing a high-capacity NCM811 (LiNi0.8Co0.1Mn0.1O2), and the decomposition behavior has been delineated through X-ray photoelectron spectroscopy (XPS). An evaluation and comparison of moisture stability have been conducted using transmission electron microscope-selected-area electron diffraction (TEM-SAED), and the sites of oxygen substitution have been meticulously identified utilizing Rietveld refinement and Raman spectroscopy. A mechanism positing the stabilization of the PS4 unit, pivotal for moisture resistance through oxygen-mediated structural evolution, is proposed. Furthermore, the significance of the SE in facilitating the commercial viability of sulfide-based ASSBs, accompanied by a substantial enhancement in battery performance, has been elucidated. References Janek and W. G. Zeier, Nature Energy, 2016, 1, 16141.Muramatsu, A. Hayashi, T. Ohtomo, S. Hama and M. Tatsumisago, Solid State Ionics, 2011, 182, 116-119.Sun, Y. Lai, N. Lv, Y. Hu, B. Li, L. Jiang, J. Wang, S. Yin, K. Li and F. Liu, ACS Appl Mater Interfaces, 2021, 13, 54924-54935.Hwang, Y.-J. Lee, S. R. Lee, Y.-C. Ha, M. Cho, S.-M. Lee and K. Cho, Journal of Materials Chemistry A, 2022, 10, 16908-16919.

Structure-performance relationship and molecular structure optimization design of acid phosphate ester extractants

The extraction performance of acid phosphate ester extractants (PEEs) decreases significantly as the acidity of the aqueous phase increases. Therefore, finding PEEs suitable for high-acid environments has become critical to addressing their performance attenuation. However, the unclear structure-performance relationship of PEEs has led to a lack of guidance in experimental synthesis, significantly impeding the emergence of new acid-resistant PEEs. To tackle these issues, ten novel phenyl phosphate ester extractants were designed based on the molecular formula of phosphodiester (R1R2P(=O)OH) and the conjugation effect of the benzene ring. The relationship between the intrinsic extraction performance of acid PEEs and substituent groups (phenoxy, alkoxy, and alkyl) was quantitatively established by calculating the Gibbs free energy changes of three primary reactions (dimer dissociation, monomer acid ionization, and metal coordination) during divalent cobalt ion extraction. Additionally, the impact of different substitution sites (para, meta, and ortho) of the benzene ring on the extraction performance of acid PEEs was studied. The results indicated that introducing phenoxy groups into traditional acid PEEs (P204 and P507) can effectively enhance the extractants’ acid ionization ability and thermodynamic driving force. The extraction performance of acid PEEs is positively correlated with the number of phenoxy groups, and carbon chain substitution at the meta-position of the benzene ring is the most advantageous. By screening five low-toxicity and low-cost phenolic hydroxyl reagents currently available on the market, design a phenyl phosphate ester extractant ([(CH3)3CCH2C(CH3)2C6H4O]2P(=O)OH, P-4TO) that combines cost and performance advantages. Furthermore, the transition state theory was used to confirm the feasibility of preparing P-4TO, which provided a comprehensive theoretical research method for the future design and synthesis of efficient PEEs.

Adsorption of ɳ2 (O, C)-tilted formaldehyde geometry on transition metal substituted p(2 × 1) SnO2 (1 1 0) surface: A first-principles analysis

Density Functional Theory was used to study the adsorption mechanisms of bidentate η2(O, C)-tilted formaldehyde on SnO2 (110) surfaces modeled with a p(2 × 1) periodicity and substituted with transition metals (Au, Cu, Ni, Pd). Formation energies identified suitable substitution sites between Sn5c and Sn6c for each of the selected dopant atoms. Except for Pd, the other dopants were found to be more stably substituted at the five-fold coordinated Sn site. Adsorption energy analysis showed that Ni and Pd substitutions enhanced adsorption compared to the pristine SnO2 (110) surface by 0.038 eV and 0.077 eV, respectively. Pd substitution in the first two surface layers had the highest negative adsorption energy, showcasing a maximum increment by 0.101 eV, but its co-substitution with Ni did not yield improved adsorption. Bader charge analysis confirmed a two-fold charge transfer from the surface Sn5c site to OHCHO atom and from CHCHO atom to the surface O2c site, which is attributed to the diagonal-span bridged configuration of the η2(O, C) bidenate formaldehyde. The charge transfer from the surface to the gas molecule was found to be the highest for the Pd co-substituted SnO2 surface (|1.332|e). The charge transfer is visually supported by charge density plots. Pd substitution was seen to introduce additional states at the Fermi energy. On the other hand, the introduction of the gas molecule predominantly injected additional states for the Ni-substituted surface, thereby improving the adsorption mechanism. Recovery times were calculated using the transition state equation, with values ranging from 7 to 11 s for the effectively substituted surfaces.

Importing Atomic Rare‐Earth Sites to Activate Lattice Oxygen of Spinel Oxides for Electrocatalytic Oxygen Evolution

AbstractSpinel oxides have emerged as highly active catalysts for the oxygen evolution reaction (OER). Owing to covalency competition, the OER process on spinel oxides often follows an arduous adsorbate evolution mechanism (AEM) pathway. Herein, we propose a novel rare‐earth sites substitution strategy to tune the lattice oxygen redox of spinel oxides and bypass the AEM scaling relationship limitation. Taking NiCo2O4 as a model, the incorporation of Ce into the octahedral site induces the formation of Ce−O−M (M=Ni, Co) bridge, which triggers charge redistribution within NiCo2O4. The developed Ce−NiCo2O4 exhibits remarkable OER activity with a low overpotential, satisfactory electrochemical stability, and good practicability in anion‐exchange membrane water electrolyzer. Theoretical analyses reveal that OER on Ce−NiCo2O4 surface follows a more favorable lattice oxygen mechanism (LOM) pathway and non‐concerted proton‐electron transfers compared to pure NiCo2O4, as also verified by pH‐dependent behavior and in situ Raman analysis. The 18O‐labeled electrochemical mass spectrometry provides direct evidence that the oxygen released during the OER originates from the lattice oxygen of Ce−NiCo2O4. We discover that electron delocalization of Ce 4f states triggers charge redistribution in NiCo2O4 through the Ce−O−M bridge, favoring antibonding state occupation of Ni−O bonding in [Ce−O−Ni] unit site, thereby activating lattice oxygen redox of NiCo2O4 in OER. This work provides a new perspective for designing highly active spinel oxides for OER and offers significant insights into the rare‐earth‐enhanced LOM mechanism.