A high-spin diradical dianion and its bridged chemically switchable single-molecule magnet.

Triplet diradicals have attracted tremendous attention due to their promising application in organic spintronics, organic magnets and spin filters. However, very few examples of triplet diradicals with singlet-triplet energy gaps (Δ ) over 0.59 kcal mol (298 K) have been reported to date.

Emerging Investigator Series: COVID-19 lockdown effects on aerosol particle size distributions in northern Italy.

The lockdown measures implemented to curb the COVID-19 epidemic in Italy reduced human mobility dramatically, which resulted in a marked decline in traffic intensity. In this study, we present the effect of lockdown measures on several air pollutants, particle number size distribution as well as on regional new particle formation (NPF) frequency in the Po Valley (northern Italy). The results show that during the lockdown period, concentrations of nitrogen dioxide (NO), nitric oxide (NO), benzene (CH), and toluene (CH) decreased, while ozone (O) concentrations mildly increased as compared to the corresponding period in 2016-2019.

Translating daily COVID-19 screening into a simple glucose test: a proof of concept study.

Home testing is an attractive emerging strategy to combat the COVID-19 pandemic and prevent overloading of healthcare resources through at-home isolation, screening and monitoring of symptoms. However, current diagnostic technologies of SARS-CoV-2 still suffer from some drawbacks because of the tradeoffs between sensitivity, usability and costs, making the test unaffordable to most users at home. To address these limitations, taking advantage of clustered regularly interspaced short palindromic repeats (CRISPRs) and a portable glucose meter (PGM), we present a proof-of-concept demonstration of a target-responsive CRISPR-PGM system for translating SARS-CoV-2 detection into a glucose test.

Delivering Antisense Oligonucleotides across the Blood-Brain Barrier by Tumor Cell-Derived Small Apoptotic Bodies.

The blood-brain barrier (BBB) is the most restrictive and complicated barrier that keeps most biomolecules and drugs from the brain. An efficient brain delivery strategy is urgently needed for the treatment of brain diseases. Based on the studies of brain-targeting extracellular vesicles (EVs), the potential of using small apoptotic bodies (sABs) from brain metastatic cancer cells for brain-targeting drug delivery is explored.

Black Carbon Emission Reduction Due to COVID-19 Lockdown in China.

During the Lunar New Year Holiday of 2020, China implemented an unprecedented lockdown to fight the COVID-19 outbreak, which strongly affected the anthropogenic emissions. We utilized elemental carbon observations (equivalent to black carbon, BC) from 42 sites and performed inverse modeling to determine the impact of the lockdown on the weekly BC emissions and quantify the effect of the stagnant conditions on BC observations in densely populated eastern and northern China. BC emissions declined 70% (eastern China) and 48% (northern China) compared to the first half of January.

Clickable amino acid tuned self-assembly of a nucleus-selective multi-component nanoplatform for synergistic cancer therapy.

Nucleus-targeted therapy holds great promise in cancer treatment; however, a lack of effective nucleus-specific delivery significantly limits its application potential. Here, we report a nucleus-targeted synergistic chemo-photodynamic therapy based on the self-assembly of chlorin e6 (Ce6) and doxorubicin (DOX) tuned by clickable dibenzocyclooctyne (DIBO) functionalized lysine () and subsequent reaction with crosslinkers. The assembled nanodrugs with high loading efficiency and long-term stability show enhanced cellular uptake and accumulation in the nucleus, resulting in greatly improved and chemo-photodynamic efficacy.

Electrogenerated chemiluminescence detection of single entities.

Electrogenerated chemiluminescence, also known as electrochemiluminescence (ECL), is an electrochemically induced production of light by excited luminophores generated during redox reactions. It can be used to sense the charge transfer and related processes at electrodes a simple visual readout; hence, ECL is an outstanding tool in analytical sensing. The traditional ECL approach measures averaged electrochemical quantities of a large ensemble of individual entities, including molecules, microstructures and ions.

Correction: Rhodium-catalysed selective C-C bond activation and borylation of cyclopropanes.

[This corrects the article DOI: 10.1039/D0SC06186G.].

Cd-driven surface reconstruction and photodynamics in gold nanoclusters.

With atomically precise gold nanoclusters acting as a starting unit, substituting one or more gold atoms of the nanocluster with other metals has become an effective strategy to create metal synergy for improving catalytic performances and other properties. However, so far detailed insight into how to design the gold-based nanoclusters to optimize the synergy is still lacking, as atomic-level exchange between the surface-gold (or core-gold) and the incoming heteroatoms is quite challenging without changing other parts. Here we report a Cd-driven reconstruction of Au(DMBT) (DMBT = 3,5-dimethylbenzenethiol), in which four Au(DMBT) staples are precisely replaced by two AuCd(DMBT) staples to form AuCd(DMBT) with the face-centered cubic inner core retained.

Snapshotting the transient conformations and tracing the multiple pathways of single peptide folding using a solid-state nanopore.

A fundamental question relating to protein folding/unfolding is the time evolution of the folding of a protein into its precisely defined native structure. The proper identification of transition conformations is essential for accurately describing the dynamic protein folding/unfolding pathways. Owing to the rapid transitions and sub-nm conformation differences involved, the acquisition of the transient conformations and dynamics of proteins is difficult due to limited instrumental resolution.

The video-rate imaging of sub-10 nm plasmonic nanoparticles in a cellular medium free of background scattering.

Plasmonic nanoparticles (, gold, silver) have attracted much attention for biological sensing and imaging as promising nanoprobes. Practical biomedical applications demand small gold nanoparticles (Au NPs) with a comparable size to quantum dots and fluorescent proteins. Very small nanoparticles with a size below the Rayleigh limit (usually <30-40 nm) are hard to see by light scattering using a dark-field microscope, especially within a cellular medium.

Discovery and biosynthesis of guanipiperazine from a NRPS-like pathway.

Nonribosomal peptide synthetases (NRPSs) are modular enzymes that use a thiotemplate mechanism to assemble the peptide backbones of structurally diverse and biologically active natural products in bacteria and fungi. Unlike these canonical multi-modular NRPSs, single-module NRPS-like enzymes, which lack the key condensation (C) domain, are rare in bacteria, and have been largely unexplored to date. Here, we report the discovery of a gene cluster () encoding a NRPS-like megasynthetase through genome mining.

Redox-active benzimidazolium sulfonamides as cationic thiolating reagents for reductive cross-coupling of organic halides.

Redox-active benzimidazolium sulfonamides as thiolating reagents have been developed for reductive C-S bond coupling. The IMDN-SOR reagent provides a bench-stable cationic precursor to generate a portfolio of highly active N-S intermediates, which can be successfully applied in cross-electrophilic coupling with various organic halides. The employment of an electrophilic sulfur source solved the problem of catalyst deactivation and avoided odorous thiols, featuring practical conditions, broad substrate scope, and excellent tolerance.

A highly selective decarboxylative deuteration of carboxylic acids.

In this paper, we report a mild and practical method for precise deuteration of aliphatic carboxylic acids by synergistic photoredox and HAT catalysis. The reaction delivers excellent D-incorporation (up to 99%) at predicted sites even in substrates bearing reactive C-H bonds or versatile functional groups. The use of a recirculation reactor with a peristaltic pump supports a scalable preparative ability (up to 50 mmol) under very mild reaction conditions.

High-resolution imaging of catalytic activity of a single graphene sheet using electrochemiluminescence microscopy.

Here, the electrocatalytic activity of a single graphene sheet is mapped using electrochemiluminescence (ECL) microscopy with a nanometer resolution. The achievement of this high-spatial imaging relies on the varied adsorption of hydrogen peroxide at different sites on the graphene surface, leading to unsynchronized ECL emission. By shortening the exposure time to 0.

Surmounting tumor resistance to metallodrugs by co-loading a metal complex and siRNA in nanoparticles.

Copper complexes are promising anticancer agents widely studied to overcome tumor resistance to metal-based anticancer drugs. Nevertheless, copper complexes encounter drug resistance from time to time. Adenosine-5'-triphosphate (ATP)-responsive nanoparticles containing a copper complex CTND and B-cell lymphoma 2 (Bcl-2) small interfering RNA (siRNA) were constructed to cope with the resistance of cancer cells to the complex.

Intrinsic activity modulation and structural design of NiFe alloy catalysts for an efficient oxygen evolution reaction.

NiFe alloy catalysts have received increasing attention due to their low cost, easy availability, and excellent oxygen evolution reaction (OER) catalytic activity. Although it is considered that the co-existence of Ni and Fe is essential for the high catalytic activity, the identification of active sites and the mechanism of OER in NiFe alloy catalysts have been controversial for a long time. This review focuses on the catalytic centers of NiFe alloys and the related mechanism in the alkaline water oxidation process from the perspective of crystal structure/composition modulation and structural design.

Rhodium-catalysed selective C-C bond activation and borylation of cyclopropanes.

Transition metal (TM)-catalysed directed hydroboration of aliphatic internal olefins which facilitates the construction of complex alkylboronates is an essential synthetic methodology. Here, an efficient method for the borylation of cyclopropanes involving TM-catalysed directed C-C activation has been developed. Upon exposure to neutral Rh(i)-catalyst systems, -Piv-substituted cyclopropylamines (CPAs) undergo proximal-selective hydroboration with HBpin to provide valuable γ-amino boronates in one step which are otherwise difficult to synthesize by known methods.

Efficient antigen cross-presentation through coating conventional aluminum adjuvant particles with PEI.

Classical aluminum adjuvant is a deficient antigen carrier for cross-presentation and cross-priming of CD8 cytotoxic T cells. Our previous research has demonstrated that cross-presentation efficiency significantly increased when antigens are conjugated covalently to α-AlO nanoparticles. Here we found that coating conventional aluminum adjuvants with polyethyleneimine (PEI) could enhance antigen cross-presentation of DCs (dendritic cells) in vitro and in vivo.

A serological aptamer-assisted proximity ligation assay for COVID-19 diagnosis and seeking neutralizing aptamers.

Rapid and accurate diagnosis of COVID-19 plays an essential role in the current epidemic prevention and control. Despite the promise of nucleic acid and antibody tests, there is still a great challenge to reduce the misdiagnosis, especially for asymptomatic individuals. Here we report a generalizable method for highly specific and ultrasensitive detection of serum COVID-19-associated antigens based on an aptamer-assisted proximity ligation assay.

A FRET-based fluorescent Zn sensor: 3D ratiometric imaging, flow cytometric tracking and cisplatin-induced Zn fluctuation monitoring.

Monitoring labile Zn homeostasis is of great importance for the study of physiological functions of Zn in biological systems. Here we report a novel ratiometric fluorescent Zn sensor, CPBT, which was constructed based on chelation-induced alteration of FRET efficiency. CPBT was readily cell membrane permeable and showed a slight preferential localization in the endoplasmic reticulum.

Spatially resolved electrochemiluminescence through a chemical lens.

Electrochemiluminescence (ECL) microscopy is an emerging technique with a wide range of imaging applications and unique properties in terms of high spatial resolution, surface confinement and favourable signal-to-noise ratio. Despite its successful analytical applications, tuning the depth of field (, thickness of the ECL-emitting layer) is a crucial issue. Indeed, the control of the thickness of this ECL region, which can be considered as an "evanescent" reaction layer, limits the development of cell microscopy as well as bioassays.

A ratiometric fluorescent probe for real-time monitoring of intracellular glutathione fluctuations in response to cisplatin.

Real-time imaging of fluctuations in intracellular glutathione (GSH) concentrations is critical to understanding the mechanism of GSH-related cisplatin-resistance. Here, we describe a ratiometric fluorescence probe based on a reversible Michael addition reaction of GSH with the vinyl-functionalized boron-dipyrromethene (4,4-difluoro-4-bora-3,4-diaza--indacene or BODIPY) . The probe was applied for real-time monitoring of the fluctuations in GSH levels in cells under cisplatin treatment.

Small molecule-mediated co-assembly of amyloid-β oligomers reduces neurotoxicity through promoting non-fibrillar aggregation.

Amyloid-β (Aβ) oligomers, particularly low molecular weight (LMW) oligomers, rather than fibrils, contribute very significantly to the onset and progression of Alzheimer's Disease (AD). However, due to the inherent heterogeneity and metastability of oligomers, most of the conventional anti-oligomer therapies have indirectly modulated oligomers' toxicity through manipulating Aβ self-assembly to reduce oligomer levels, which are prone to suffering from the risk of regenerating toxic oligomers from the products of modulation. To circumvent this disadvantage, we demonstrate, for the first time, rational design of rigid pincer-like scaffold-based small molecules with blood-brain barrier permeability that specifically co-assemble with LMW Aβ oligomers through directly binding to the exposed hydrophobic regions of oligomers to form non-fibrillar, degradable, non-toxic co-aggregates.