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Valley-dependent excitation and emission in transition metal dichalcogenides (TMDCs) have recently emerged as a new avenue for optical data manipulation, quantum optical technologies, and chiral photonics. The valley-polarized electronic states can be optically addressed through photonic spin-orbit interaction of excitonic emission, typically with plasmonic nanostructures, but their performance is limited by the low quantum yield of neutral excitons in TMDC multilayers and the large Ohmic loss of plasmonic systems. Here, we demonstrate a valleytronic system based on the trion emission in high-quantum-yield WS2 monolayers chirally coupled to a low-loss microfiber. The integrated system uses the spin properties of the waveguided modes to achieve long-range directional routing of valley excitations and also provides an approach to selectively address valley-dependent emission from different spatial locations around the microfiber. This valleytronic interface can be integrated with fiber communication devices, allowing for merging valley polarization and chiral photonics as an alternative mechanism for optical information transport and manipulation in classical and quantum regimes.

Title on author’s file: Electrochemical generation of ruthenium (IV)–oxo complexes : an unexpected promotion effects from the alkyl-tailed ligand and anions

Pectobacterium carotovorum is a Gram-negative plant-specific pathogen that causes severe rot of postharvest vegetables. Given the safety consideration of pesticides, we developed a peptide approach...

From a geometrical perspective, a chiral object does not have mirror planes or inversion symmetry. It exhibits the same physical properties as its mirror image (enantiomer), except for the chiroptical activity, which is often the opposite. Recent advancements have identified particularly interesting implications of chirality on the optical properties of metal nanoparticles, which are intimately related to localized surface plasmon resonance phenomena. Although such resonances are usually independent of the circular polarization of light, specific strategies have been applied to induce chirality, both in assemblies and at the single-particle level. In this tutorial review, we discuss the origin of plasmonic chirality, as well as theoretical models that have been proposed to explain it. We then summarise recent developments in the synthesis of discrete nanoparticles with plasmonic chirality by means of wet-chemistry methods. We conclude with a discussion of promising applications for discrete chiral nanoparticles. We expect this tutorial review to be of interest to researchers from a wide variety of disciplines where chiral plasmonics can be exploited at the nanoparticle level, such as chemical sensing, photocatalysis, photodynamic or photothermal therapies, etc.

Direct seawater electrolysis opens a new opportunity to lower the cost of hydrogen production from current water electrolysis technologies. To facilitate its commercialization, the challenges of long-term performance stability of electrochemical devices need to be first addressed and realized. This minireview summarised the common causes of performance decline during seawater electrolysis, from chemical reactions at the electrode surface to physical damage to the cell. The problems triggered by the impurities in seawater are specifically discussed. Following these issues, we further outlined the ongoing effort of counter-measurements: from electrocatalyst optimization to electrode engineering and cell design. The recent progress in selectivity tuning, surface protection, gas diffusion, and cell configuration is highlighted. In the final remark, we emphasized the need for a consensus on evaluating the stability of seawater electrolysis in the current literature.

A series of isatin derivatives bearing three different substituent groups at the N-1, C-3 and C-5 positions of the isatin scaffold were systematically designed and synthesized to study the structure–activity relationship of their inhibition of bacterial peptidoglycan glycosyltransferase (PGT) activity and antimicrobial susceptibility against S. aureus, E. coli and methicillin-resistant Staphylococcus aureus (MRSA (BAA41)) strains. The substituents at these sites are pointing towards three different directions from the isatin scaffold to interact with the amino acid residues in the binding pocket of PGT. Comparative studies of their structure–activity relationship allow us to gain better understanding of the direction of the substituents that contribute critical interactions leading to inhibition activity against the bacterial enzyme. Our results indicate that the modification of these sites is able to maximize the antimicrobial potency and inhibitory action against the bacterial enzyme. Two compounds show good antimicrobial potency (MIC = 3 μg mL−1 against S. aureus and MRSA; 12–24 μg mL−1 against E. coli). Results of the inhibition study against the bacterial enzyme (E. coli PBP 1b) reveal that some compounds are able to achieve excellent in vitro inhibitions of bacterial enzymatic activity (up to 100%). The best half maximal inhibitory concentration (IC50) observed among the new compounds is 8.9 μM.

The effective strategies to neutralize the New Delhi metallo-β-lactamase (NDM-1) activity offer unique opportunities to combination therapy because NDM-1 inactivates all classes of carbapenem antibiotics, which are widely regarded as the last resort of drugs for treating serious bacterial infections. Here we describe the efficient construction of a series of trans-1,3,4-trisubstituted pyrrolidines via boric acid-catalyzed 1,3-dipolar cycloaddition of N-benzylazomethine ylide with methyl ferulate for the biological evaluation of their cytotoxicity and synergistic activity in combination with meropenem towards NDM-1 positive carbapenem-resistant Enterobacteriaceae (CRE). The cell-based screens generated one promising hit, namely compound 10e, which exhibited low cytotoxicity (IC50 > 128 μM), moderate NDM-1 enzyme inhibition (IC50 = 51 μM), and potent synergistic activity against a panel of clinically isolated NDM-1 positive CRE with fractional inhibitory concentration indexes ranging from 0.01 to 0.25. Structure–activity relationship studies revealed that the zinc-chelating moiety of 2-(bis(pyridin-2-ylmethyl)-amino)acetyl group of compound 10e plays a pivotal role for potent activity. Regarding the inhibition mechanism, a series of biochemical assays revealed that compound 10e may inactivate NDM-1 activity by displacing both zinc ions from the active site of the enzyme. Altogether, our studies indicate that compound 10e represents an important pyrrolidine-type scaffold targeting NDM-1, providing a promising starting point to be further developed as carbapenem antibiotic adjuvants.

The chromosomal blaOXA-51-type gene encodes carbapenem-hydrolyzing class D β-lactamases (CHDLs), specific variants shown to mediate carbapenem resistance in the Gram-negative bacterial pathogen Acinetobacter baumannii. This study aims to characterize the effect of key amino acid substitutions in OXA-51 variants of carbapenem-hydrolyzing class D β-lactamases (CHDLs) on substrate catalysis. Mutational and structural analyses indicated that each of the L167V, W222G, or I129L substitutions contributed to an increase in catalytic activity. The I129L mutation exhibited the most substantial effect. The combination of W222G and I129L substitutions exhibited an extremely strong catalytic enhancement effect in OXA-66, resulting in higher activity than OXA-23 and OXA-24/40 against carbapenems. These findings suggested that specific arrangement of residues in these three important positions in the intrinsic OXA-51 type of enzyme can generate variants that are even more active than known CHDLs. Likewise, mutation leading to the W222M change also causes a significant increase in the catalytic activity of OXA-51. blaOXA-51 gene in A. baumannii may likely continue to evolve, generating mutant genes that encode carbapenemase with extremely strong catalytic activity.

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) are emerging as promising building blocks of high-performance photocatalysts for visible-light-driven water splitting because of their unique physical, chemical, electronic, and optical properties. This review focuses on the fundamentals of 2D TMDC-based mixed-dimensional heterostructures and their unique properties as visible-light-driven photocatalysts from the perspective of dimensionality and interface engineering. First, we discuss the approaches and advantages of surface modification and functionalization of 2D TMDCs for photocatalytic water splitting under visible-light illumination. We then classify the strategies for improving the photocatalytic activity of 2D TMDCs via combination with various low-dimensional nanomaterials to form mixed-dimensional heterostructures. Further, we highlight recent advances in the use of these mixed-dimensional heterostructures as high-efficiency visible-light-driven photocatalysts, particularly focusing on synthesis routes, modification approaches, and physiochemical mechanisms for improving their photoactivity. Finally, we provide our perspectives on future opportunities and challenges in promoting real-world photocatalytic applications of 2D TMDC-based heterostructures.

Given the worldwide prevalence of pathogenic drug-resistant bacteria and the slow pace of new antibacterial development, discovering new uses for approved drugs that are outside the scope of the or...

Photochemical hydrogen generation from water is a promising solution to concurrently tackle energy and environmental problems. However, the solar-to-hydrogen conversion efficiencies of most photocatalysts are still unsatisfactory due to two major limiting factors: the non-ideal band structure of photocatalysts and the fast recombination of photo-generated charge carriers. Herein, we report a Janus-type TiO2 heterojunction consisting of ordered blue-anatase and disordered black-rutile phases fabricated by the magnesiothermic reduction process. In this process, the surface enthalpy difference of rutile and anatase phases in P25-TiO2 allows the phase-selective reduction to afford novel blue ordered/disordered Janus heterostructure. The joint effect of the improved light absorption and charge separation by the disordered black-rutile phase and the high catalytic activity of the ordered blue-anatase phase, as well as the morphological advantage over order@disorder core–shell structures, significantly enhances the photocatalytic hydrogen production rate to 1.56 mmol h−1 g−1 (11.53 mmol h−1 g−1 with ∼1 wt% Pt), which delivers 13-fold enhancement compared to pristine P25-TiO2.

We investigate the geometric and electronic properties of single-atom catalysts (SACs) within metal-organic frameworks (MOFs) with respect to electrocatalytic CO2 reduction as a model reaction. A series of mid-to-late 3d transition metals have been immobilised within the microporous cavity of UiO-66-NH2. By employing Rietveld refinement of new-generation synchrotron diffraction, we not only identified the crystallographic and atomic parameters of the SACs that are stabilised with a robust MN(MOF) bonding of ca. 2.0 Å, but also elucidated the end-on coordination geometry with CO2. A volcano trend in the FEs of CO has been observed. In particular, the confinement effect within the rigid MOF can greatly facilitate redox hopping between the Cu SACs, rendering high FEs of CH4 and C2H4 at a current density of -100 mA cm-2. Although only demonstrated in selected SACs within UiO-66-NH2, this study sheds light on the rational engineering of molecular interactions(s) with SACs for the sustainable provision of fine chemicals.

New Delhi metallo-β-lactamase 1 (NDM-1) is an important causative factor of antimicrobial resistance due to its efficient hydrolysis of a broad range of β-lactam compounds. The two zinc ions at the active site play essential roles in the NDM-1 catalytic activities. In a previous work, H116, one of the three ligands at the Zn1 site, was mutated in order to investigate the nature of zinc ion chelation. We report here the crystal structure of the NDM-1 H116Q mutant, that was designed to convert a B1 di-zinc enzyme into a B3 type, which either still binds two zinc ions or binds only one at the Zn2 site. The effect of mutation on the overall structure is minimal. Unexpectedly, no zinc ion was observed in the crystal structure. The Zn2-site ligating residue C221 forms a covalent bond with the nearby K121, a residue important in maintaining the active-site structure. The largest conformational changes were found at main-chain and side-chain atoms at residues 232-236 (loop 10), the proper configuration of which is known to be essential for substrate binding. The catalytic-site mutation caused little local changes, yet the effects were amplified and propagated to the substrate binding residues. There were big changes in the ψ angles of residues G232 and L234, which resulted in the side chain of N233 being displaced away from the substrate-binding site. In summary, we failed in turning a B1 enzyme into a B3 enzyme, yet we produced a zinc-less NDM-1 with residual activities.

In this work, by capping a macrolactam ring at the C-terminus of a de novo-designed peptide, namely zp80, we have constructed a small peptide library via the solid phase peptide synthesis for screening. Eight peptides bearing different aspartic acid-rich macrolactam rings but the same linear (IIRR)

Valley-dependent excitation and emission in transition metal dichalcogenides (TMDCs) have recently emerged as a new avenue for optical data manipulation, quantum optical technologies, and chiral photonics. The valley-polarized electronic states can be optically addressed through photonic spin-orbit interaction of excitonic emission, typically with plasmonic nanostructures, but their performance is limited by the low quantum yield of neutral excitons in TMDC multilayers and the large Ohmic loss of plasmonic systems. Here, we demonstrate a valleytronic system based on the trion emission in high-quantum-yield WS

Precisely tuning the nuclearity of supported metal nanoclusters is pivotal for designing more superior catalytic systems, but it remains practically challenging. By utilising the chemical and molecular specificity of UiO-66-NH2 (a Zr-based metal–organic framework), we report the controlled synthesis of supported bi- and trinuclear Cu-oxo nanoclusters on the Zr6O4 nodal centres of UiO-66-NH2. We revealed the interplay between the surface structures of the active sites, adsorption configurations, catalytic reactivities and associated reaction energetics of structurally related Cu-based ‘single atoms’ and bi- and trinuclear species over our model photocatalytic formic acid reforming reaction. This work will offer practical insight that fills the critical knowledge gap in the design and engineering of new-generation atomic and nanocluster catalysts. The precise control of the structure and surface sensitivities is important as it can effectively lead to more reactive and selective catalytic systems. The supported bi- and trinuclear Cu-oxo nanoclusters exhibit notably different catalytic properties compared with the mononuclear ‘Cu1’ analogue, which provides critical insight for the engineering of more superior catalytic systems., The controlled synthesis of novel bi- and trinuclear Cu-oxo nanoclusters supported on UiO-66-NH2 that show notably different catalytic properties in the photocatalytic formic acid decomposition reaction is reported.

Nanozymes, an emerging family of heterogeneous nanomaterials with enzyme-like characteristics, offer significant advantages as alternatives to natural enzymes for diverse biocatalytic applications. Nevertheless, the inhomogeneous configuration of nanomaterials makes it extremely challenging to develop nanozymes of desired performance and reaction mechanism. Single-atom nanozymes (SAzymes) that are composed of single-atomic active sites may provide an answer to these challenges with remarkable enzyme-like activity and specificity. The well-defined coordination microenvironments of SAzymes offer a suitable model system to investigate the structure-activity relationship and thus bridge the gap between natural enzyme and nanozyme. In this review, we would first present an overview of discoveries, advantages, and classifications of SAzymes. Then, we would discuss the reaction mechanism, design principles, and biosensing applications of a series of typical SAzymes with a focus on the rational design strategies for targeted reaction and the effort to uncover the catalytic mechanism at the atomic scale. Finally, we would provide the challenges and future perspectives of SAzymes as the next-generation nanozymes.

Recently, many TetX variants such as Tet(X3~14) were reported to confer resistance to tigecycline which is a last-resort antibiotic used to treat infections caused by multidrug-resistant bacteria. In this study, we identified essential residues including 329, 339, 340, 350, and 351 in TetX variants that mediated the evolution of the tigecycline-inactive Tet(X2) enzyme to the active forms of Tet(X3) and Tet(X4). Based on their amino acid sequences and functional features, we classified TetX variants into TetX-A class, TetX-B class and TetX-C class. We further found that TetX-A class variants originated from Bacteroidetes, with some variants further evolving to TetX-C class and acquired by Enterobacteriaceae. On the other hand, our data showed that some variants genes belonging to TetX-A class evolved directly to TetX-B class, which was further transmitted to Acinetobacter spp. This new classification system may facilitate better clinical management of patients infected by TetX-producing strains.

Inhibition of bacterial cell division is a novel mechanistic action in the development of new antimicrobial agents. The FtsZ protein is an important antimicrobial drug target because of its essential role in bacterial cell division. In the present study, potential inhibitors of FtsZ were identified by virtual screening followed by in vivo and in vitro bioassays. One of the candidates, Dacomitinib (S2727), shows for the first time its potent inhibitory activity against the MRSA strains. The binding mode of Dacomitinib in FtsZ was analyzed by docking, and Asp(199) and Thr(265) are thought to be essential residues involved in the interactions.

Reported here is the first crystallographic observation of stereospecific bindings of l- and d-lysine (Lys) in achiral MFI zeolites. The MFI structure offers inherent geometric and internal confinement effects for the enantiomeric difference in l- and d-Lys adsorption. Notable differences have been observed by circular dichroism (CD) spectroscopy and thermogravimetric analysis (TGA). Distinct l- and d-Lys adsorption behaviours on the H-ZSM-5 framework have been revealed by the Rietveld refinement of high-resolution synchrotron X-ray powder diffraction (SXRD) data and the density-functional theory (DFT) calculations. Despite demonstrating the approach for l- and d-Lys over MFI zeolites at an atomistic resolution, the differential adsorption study sheds light on the rational engineering of molecular interaction(s) with achiral microporous materials for chiral separation purposes.

Monitoring the β-lactam antibiotic level has been an important task in food industry and clinical practice. Here, we report the development of a fluorescent PenP β-lactamase, PenP-E166Cf/N170Q, for efficient β-lactam antibiotic detection. It was constructed by covalently attaching fluorescein onto the active-site entrance of a thermostable E166Cf/N170Q mutant of a Bacillus licheniformis PenP β-lactamase. It gave a fluorescence turn-on signal toward various β-lactam antibiotics, where the fluorescence enhancement was attributed to the acyl–enzyme complex formed between PenP-E166Cf/N170Q and the β-lactam antibiotic. It demonstrated enhanced signal stability over its parental PenP-E166Cf because of the suppressed hydrolytic activity by the N170Q mutation. Compared with our previously constructed PenPC-E166Cf biosensor, PenP-E166Cf/N170Q was more thermostable and advanced in detecting β-lactams in terms of response time, signal stability, and detection limit. Positive fluorescence signals generated by E166Cf/N170Q in response to the penicillin-containing milk and mouse serum illustrated the feasibility of the biosensor for antibiotic detection in real samples. Taken together, our findings suggest the potential application of PenP-E166Cf/N170Q in biosensing β-lactam antibiotics.

Background. Urinary tract infection (UTI) is the most common bacterial infection in the world. Some cases can have serious complication as death by septic shock. With the increasing spread of multidrug-resistant bacteria, the therapeutic possibilities against the complicated UTI are exhausted, forcing the use of broad-spectrum antibiotics such as meropenem. Objectives. To evaluate the penetrating ability of meropenem to renal tissue using an enzymatic biosensor in samples of renal cortex and its correlation with plasma levels. Method. We conducted a descriptive study in humans with indication of kidney biopsy. Meropenem was administered 1 hour before performing the biopsy, and the concentrations of meropenem in a series of samples of plasma and renal biopsy were determined. Results. Renal biopsy and plasma samples of 14 patients, 64% women with body mass index of 26.3 kg/m2 (SD ± 2.9) and estimated glomerular filtration rate of 57.5 mL/min/1.73 m2 (SD ± 44.1), were examined. Renal biopsy was done at 68.9 minutes (SD ± 20.3), and the second plasma sample was obtained at 82.1 minutes (SD ± 21.2) and the third at 149.6 minutes (SD ± 31.5). The mean kidney meropenem concentration was 3.1 μg/mL (SD ± 1.9). For each patient, a decay curve of plasma meropenem concentration was constructed. The proportion of meropenem concentrations in renal tissue and plasma at biopsy moment was 14% (SD ± 10) with an interquartile range of 5.5–20.3%. With normal renal function, meropenem can achieve a bactericidal effect towards bacteria with MIC-90 μg/mL in the renal parenchyma. Conclusions. Meropenem is effective to treat the most frequent uropathogens with the bactericidal effect. Nevertheless, for resistant bacteria, it is necessary to adjust the dose to achieve adequate parenchymal concentration.

Complex nanostructures with distinct spatial architectures and more active sites hold broad prospects in new energy conversion fields. Herein, a facile strategy was carried out to construct triple-...

Understanding carboxyl-metal ligand interaction has great significance in analytical chemistry. Herein, we use resonant surface-enhanced Raman scattering (SERS) to probe the physiochemical interaction and conformation change in several metal ion-carboxyl coordination complex systems adsorbed on the surface of plasmonically resonant metal nanostructures. Our SERS results and density function theory calculations jointly reveal that low-valence metal ions (such as K

Background: The intraoperative visualization of tumor cells is a powerful modality for surgical treatment of solid tumors. Since the completeness of tumor excision is closely correlated with the survival of patients, probes that can assist in distinguishing tumor cells are highly demanded. Purpose: In the present study, a fluorescent probe JF1 was synthesized for imaging of tumor cells by conjugating a substrate of cathepsin B (quenching moiety) to Oregon Green derivative JF2 using a self-immolative linker. Methods: JF1 was then loaded into the folate-PEG modified CaCO3 nanoparticles. The folate receptor-targeted, pH-dependent, and cathepsin B activable CaCO3 nanoprobe was test in vitro and in vivo for tumor imaging. Results: CaCO3 nanoprobe demonstrated good stability and fast lighting ability in tumors under low pH conditions. It also showed lower fluorescence background than the single cathepsin B dependent fluorescent probe. The pH-dependent and cathepsin B controlled "turn-on" property enables precise and fast indication of tumor in vitro and in vivo. Conclusion: This strategy of controlled drug delivery enables in vivo imaging of tumor nodules with a high signal-to-noise ratio, which has great potential in surgical tumor treatment.

Two-dimensional (2D) metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs) have recently emerged as a new class of crystalline materials with ultrahigh porosity and enormous surface area. These materials have attracted vast research interest due to their unique properties originating from ultrathin thickness, highly accessible active sites, and versatile structures. With many common features, MOFs and COFs also have distinct differences, both in synthetic and application aspects, as their building components are different. This review mainly focuses on the recent advances in the synthetic approaches of 2D MOFs and COFs and their applications in energy conversion reactions and storage devices. First, we discuss various strategies recently developed for the preparation of 2D MOFs and COFs by using self-assembly, template-directed method, surfactant-directed method, solid-supported growth, and decomposition, and the different considerations needed for desired 2D MOFs and COFs are compared. Secondly, energy-related applications of 2D MOFs and COFs are summarized with discussion on the structure-reactivity relationships. Finally, we give the insights into the challenges and outlook on the future research direction for 2D MOFs and COFs.