Darobactin B Stabilises a Lateral-Closed Conformation of the BAM Complex in E. coli Cells

The β-barrel assembly machinery (BAM complex) is essential for outer membrane protein (OMP) folding in Gram-negative bacteria, and represents a promising antimicrobial target. Several conformational states of BAM have been reported, but all have been obtained under conditions which lack the unique features and complexity of the outer membrane (OM). Here, we use Pulsed Electron-Electron Double Resonance (PELDOR, or DEER) spectroscopy distance measurements to interrogate the conformational ensemble of the BAM complex in E. coli cells. We show that BAM adopts a broad ensemble of conformations in the OM, while in the presence of the antibiotic darobactin B (DAR-B), BAM′s conformational equilibrium shifts to a restricted ensemble consistent with the lateral closed state. Our in-cell PELDOR findings are supported by new cryoEM structures of BAM in the presence and absence of DAR-B. This work demonstrates the utility of PELDOR to map conformational changes in BAM within its native cellular environment.     

An Electrochemical Nanosensor for Monitoring the Dynamics of Intracellular H2O2 Upon NADH Treatment

Reactive oxygen species (ROS)-based therapeutic strategies play an important role in cancer treatment. However, in situ, real-time and quantitative analysis of intracellular ROS in cancer treatment for drug screening is still a challenge. Herein we report one selective hydrogen peroxide (H₂O₂) electrochemical nanosensor, which is prepared by electrodeposition of Prussian blue (PB) and polyethylenedioxythiophene (PEDOT) onto carbon fiber nanoelectrode. With the nanosensor, we find that the level of intracellular H₂O₂ increases with NADH treatment and that increase is dose-dependent to the concentration of NADH. High-dose of NADH (above 10 mM) can induce cell death and intratumoral injection of NADH is validated for inhibiting tumor growth in mice. This study highlights the potential of electrochemical nanosensor for tracking and understanding the role of H₂O₂ in screening new anticancer drug.     

Reversible Li Plating on Graphite Anodes through Electrolyte Engineering for Fast-Charging Batteries

The difficulties to identify the rate-limiting step cause the lithium (Li) plating hard to be completely avoided on graphite anodes during fast charging. Therefore, Li plating regulation and morphology control are proposed to address this issue. Specifically, a Li plating-reversible graphite anode is achieved via a localized high-concentration electrolyte (LHCE) to successfully regulate the Li plating with high reversibility over high-rate cycling. The evolution of solid electrolyte interphase (SEI) before and after Li plating is deeply investigated to explore the interaction between the lithiation behavior and electrochemical interface polarization. Under the fact that Li plating contributes 40 % of total lithiation capacity, the stable LiF-rich SEI renders the anode a higher average Coulombic efficiency (99.9 %) throughout 240 cycles and a 99.95 % reversibility of Li plating. Consequently, a self-made 1.2-Ah LiNi_0.5Mn_0.3Co_0.2O₂ | graphite pouch cell delivers a competitive retention of 84.4 % even at 7.2 A (6 C) after 150 cycles. This work creates an ingenious bridge between the graphite anode and Li plating, for realizing the high-performance fast-charging batteries.     

Precise Epitope Organization with Self-adjuvant Framework Nucleic Acid for Efficient COVID-19 Peptide Vaccine Construction

Peptide vaccines have advantages in easy fabrication and high safety, but their effectiveness is hampered by the poor immunogenicity of the epitopes themselves. Herein, we constructed a series of framework nucleic acids (FNAs) with regulated rigidity and size to precisely organize epitopes in order to reveal the influence of epitope spacing and carrier rigidity on the efficiency of peptide vaccines. We found that assembling epitopes on rigid tetrahedral FNAs (tFNAs) with the appropriate size could efficiently enhance their immunogenicity. Further, by integrating epitopes from SARS-CoV-2 on preferred tFNAs, we constructed a COVID-19 peptide vaccine which could induce high titers of IgG against the receptor binding domain (RBD) of SARS-CoV-2 spike protein and increase the ratio of memory B and T cells in mice. Considering the good biocompatibility of tFNAs, our research provides a new idea for developing efficient peptide vaccines against viruses and possibly other diseases.     

A Triply Negatively Charged Nanographene Bilayer with Spin Frustration

We report on the largest open-shell graphenic bilayer and also the first example of triply negatively charged radical π-dimer. Upon three-electron reduction, bilayer nanographene fragment molecule (C₉₆H₂₄Ar₆)₂ (Ar=2,6-dimethylphenyl) ( 1 ₂) was transformed to a triply negatively charged species 1 ₂^3.−, which has been characterized by single-crystal X-ray diffraction, electron paramagnetic resonance (EPR) spectroscopy and magnetic properties on a superconducting quantum interference device (SQUID). 1 ₂^3.− features a 96-center-3-electron (96c/3e) pancake bond with a doublet ground state, which can be thermally excited to a quartet state. It consists of 34 π-fused rings with 96 conjugated sp² carbon atoms. Spin frustration is observed with the frustration parameter f>31.8 at low temperatures in 1 ₂^3.−, which indicates graphene upon reduction doping may behave as a quantum spin liquid.     

Promoting CO2 Electroreduction to Multi-Carbon Products by Hydrophobicity-Induced Electro-Kinetic Retardation

Advancing the performance of the Cu-catalyzed electrochemical CO₂ reduction reaction (CO₂RR) is crucial for its practical applications. Still, the wettable pristine Cu surface often suffers from low exposure to CO₂, reducing the Faradaic efficiencies (FEs) and current densities for multi-carbon (C₂₊) products. Recent studies have proposed that increasing surface availability for CO₂ by cation-exchange ionomers can enhance the C₂₊ product formation rates. However, due to the rapid formation and consumption of *CO, such promotion in reaction kinetics can shorten the residence of *CO whose adsorption determines C₂₊ selectivity, and thus the resulting C₂₊ FEs remain low. Herein, we discover that the electro-kinetic retardation caused by the strong hydrophobicity of quaternary ammonium group-functionalized polynorbornene ionomers can greatly prolong the *CO residence on Cu. This unconventional electro-kinetic effect is demonstrated by the increased Tafel slopes and the decreased sensitivity of *CO coverage change to potentials. As a result, the strongly hydrophobic Cu electrodes exhibit C₂₊ Faradaic efficiencies of ≈90 % at a partial current density of 223 mA cm⁻², more than twice of bare or hydrophilic Cu surfaces.     

Enantio- and Diastereoselective NiH-Catalyzed Hydroalkylation of Enamides or Enecarbamates with Racemic α-Bromoamides**

Catalytic methods which control multiple stereogenic centers simultaneously are highly desirable in modern organic synthesis and chemical manufacturing. Herein, we report a regio-, enantio-, and diastereoselective NiH-catalyzed hydroalkylation process which proceeds with simultaneous control of vicinal stereocenters originating from two readily accessible partners, prochiral internal alkenes (enamides or enecarbamates) and racemic alkyl electrophiles (α-bromoamides or Katritzky salts). This reaction produces high-value β-aminoamides and their derivatives under mild conditions and with precise selectivity. Preliminary studies of the mechanism indicate that the reaction involves an enantioselective syn-hydronickelation to generate an enantiomerically enriched alkylnickel(II) species. Subsequent enantioconvergent alkylation with a racemic alkyl electrophile generates the desired product as a single stereoisomer.     

Frenkel Defect-modulated Anti-thermal Quenching Luminescence in Lanthanide-doped Sc2(WO4)3

Although large amount of effort has been invested in combating thermal quenching that severely degrades the performance of luminescent materials particularly at high temperatures, not much affirmative progress has been realized. Herein, we demonstrate that the Frenkel defect formed via controlled annealing of Sc₂(WO₄)₃:Ln (Ln=Yb, Er, Eu, Tb, Sm), can work as energy reservoir and back-transfer the stored excitation energy to Ln³⁺ upon heating. Therefore, except routine anti-thermal quenching, thermally enhanced 415-fold downshifting and 405-fold upconversion luminescence are even obtained in Sc₂(WO₄)₃:Yb/Er, which has set a record of both the Yb³⁺-Er³⁺ energy transfer efficiency (>85 %) and the working temperature at 500 and 1073 K, respectively. Moreover, this design strategy is extendable to other hosts possessing Frenkel defect, and modulation of which directly determines whether enhanced or decreased luminescence can be obtained. This discovery has paved new avenues to reliable generation of high-temperature luminescence.     

Multi-Resonance Building-Block-Based Electroluminescent Material: Lengthening Emission Maximum and Shortening Delayed Fluorescence Lifetime

Multi-resonance thermally activated delayed fluorescence (MR-TADF) materials are considered a class of organic materials with exceptional electronic and optical properties, which make them promising for the applications in organic light-emitting diodes (OLEDs). In this study, we improved, synthesized, and characterized a multiple-resonance type emitter based on the assembly of MR-building blocks (MR-BBs). By optimizing the geometric arrangement of MR-BBs, we were able to generate narrowband emission in the longer wavelength region and shorten the delayed excited-state lifetime, resulting in improved emission efficiency compared to the parent molecule. Our proof-of-concept molecule, m-DBCz, exhibited narrowband yellowish-green TADF emission with a full width at half-maximum of 32 nm and a small singlet-triplet energy gap of 0.04 eV. The OLED developed using m-DBCz as the emitter demonstrated electroluminescence at 548 nm and achieved a high external quantum efficiency (EQE) of 34.9 %. Further optimization of the device resulted in a high external quantum efficiency of 36.3 % and extremely low efficiency roll-off, with EQE values of 30.1 % and 27.7 % obtained even at high luminance levels of 50 000 and 100 000 cd m⁻². These results demonstrate the full potential of MR-TADF materials for applications on ultrahigh-luminance OLEDs.