Jing Sun

Macrocycles can restrict the rotation of substituents through steric repulsions, locking in conformations that provide or enhance the activities of pharmaceuticals, agrochemicals, aroma chemicals, and materials. In many cases, the arrangement of substituents in the macrocycle imparts an element of planar chirality. The difficulty in predicting when planar chirality will arise, as well as the limited number of synthetic methods to impart selectivity, have led to planar chirality being regarded as an irritant. We report a strategy for enantio- and atroposelective biocatalytic synthesis of planar chiral macrocycles. The macrocycles can be formed with high enantioselectivity from simple building blocks and are decorated with functionality that allows one to further modify the macrocycles with diverse structural features.

A focused laser beam traps a single aggregate of a protonated tetraphenylethene derivative, and the manipulation of the molecular structure in the aggregate is achieved by overcoming the repulsion force between the molecules, activating its aggregation‐induced emission enhancement (AIEE). The bright yellow fluorescence from the aggregate can be controlled through the laser power.

Abstract

We present spatiotemporal control of aggregation‐induced emission enhancement (AIEE) of a protonated tetraphenylethene derivative by optical manipulation. A single submicrometer‐sized aggregate is initially confined by laser irradiation when its fluorescence is hardly detectable. The continuous irradiation of the formed aggregate leads to sudden and rapid growth, resulting in bright yellow fluorescence emission. The fluorescence intensity at the peak wavelength of 540 nm is tremendously enhanced with growth, meaning that AIEE is activated by optical manipulation. Amazingly, the switching on/off of the activation of AIEE is arbitrarily controlled by alternating the laser power. This result means that optical manipulation increases the local concentration, which overcomes the electrostatic repulsion between the protonated molecules, namely, optical manipulation changes the aggregate structure. The dynamics and mechanism in AIEE controlled by optical manipulation will be discussed from the viewpoint of molecular conformation and association depending on the laser power.

When the Earth was born, it was a mess. Meteors and lightning storms likely bombarded the planet's surface where nothing except lifeless chemicals could survive. How life formed in this chemical mayhem is a mystery billions of years old. Now, a new study offers evidence that the first building blocks may have matched their environment, starting out messier than previously thought.

Spring fever: Supramolecular springs are defined as helical molecules or assemblies thereof in which the pitch can be modulated by external stimuli to achieve full control over the extension–contraction motion. In this Minireview, the structure–property relationships of supramolecular springs and spring‐like materials triggered by external stimuli are highlighted for potential future applications in responsive macroscopic devices.

Abstract

Molecular/supramolecular springs are artificial nanoscale objects possessing well‐defined structures and tunable physicochemical properties. Like a macroscopic spring, supramolecular springs are capable of switching their nanoscale conformation as a response to external stimuli by undergoing mechanical spring‐like motions. This dynamic action offers intriguing opportunities for engineering molecular nanomachines by translating the stimuli‐responsive nanoscopic motions into macroscopic work. These nanoscopic objects are reversible dynamic multifunctional architectures which can express a variety of novel properties and behave as adaptive nanoscopic systems. In this Minireview, we focus on the design and structure–property relationships of supramolecular springs and their (self‐)assembly as a prerequisite towards the generation of novel dynamic materials featuring controlled movements to be readily integrated into macroscopic devices for applications in sensing, robotics, and the internet of things.

An NHC‐Au^I complex was investigated by elaborate structural tailoring and systematic biological evaluation. It could simultaneously achieve specific imaging and inhibition of various cancer cells with negligible toxic effects on normal cells and act as a powerful radiosensitizer to boost anticancer efficacy.

Abstract

Gold(I) N‐heterocyclic carbene (Au^I‐NHC) complexes have emerged as potential anticancer agents owing to their high cytotoxicity and stability. Integration of their above unique functions with customized aggregation‐induced emission (AIE) luminogens to achieve specific bioimaging and efficient theranostics to cancer is highly desirable but is rarely studied. Now, a series of novel Au^I‐NHC compounds were developed with AIE characteristics. A complex with a PPh₃ ligand was selected out as it could achieve both prominent specific imaging of various cancer cells and efficient inhibition of their growth with negligible toxic effects on normal cells due to the targeting binding and strong inhibition towards thioredoxin reductase. This complex could also act as a powerful radiosensitizer to boost the anticancer efficacy with performance superior to that of popularly used auranofin. It holds great potential as a specific and effective theranostic drug in cancer diagnosis and precise therapy.

Strong links : Polymers containing luminophores or sub‐luminophores may display enhanced emission upon crosslinking by covalent, supramolecular, and ionic bonding, and by through‐space interactions in confined domains. In this Minireview the theoretical background is discussed and numerous examples are provided, which may guide researchers in crosslinkage techniques to improve luminescent systems.

Abstract

The crosslink‐enhanced emission effect was first proposed to explore the strong luminescence of nonconjugated polymer dots possessing only either non‐emissive or weakly emissive sub‐luminophores. Interesting phenomena in recent research indicate such enhancement caused by extensive crosslinking appears in diverse luminescent polymers with sub‐luminophores (electron‐rich heteroatomic moieties) or luminophores (conjugated π domains). This enhancement can promote the emission from nonluminous to luminous, from weakly luminous to strongly luminous, and even convert the pathway of radiative transitions. The concept of the crosslink‐enhanced emission effect should be updated and extended to an in‐depth spatial effect, such as electron overlap and energy splitting in confined domains by effective crosslinking, more than initial immobilization. This Minireview outlines the development of the crosslink‐enhanced emission effect from the perspective of the detailed classification, inherent mechanism and applicable systems. An outlook on the further exploration and application of this theory are also proposed.

An NHC‐Au^I complex was investigated by elaborate structural tailoring and systematic biological evaluation. It could simultaneously achieve specific imaging and inhibition of various cancer cells with negligible toxic effects on normal cells and act as a powerful radiosensitizer to boost anticancer efficacy.

Abstract

Gold(I) N‐heterocyclic carbene (Au^I‐NHC) complexes have emerged as potential anticancer agents owing to their high cytotoxicity and stability. Integration of their above unique functions with customized aggregation‐induced emission (AIE) luminogens to achieve specific bioimaging and efficient theranostics to cancer is highly desirable but is rarely studied. Now, a series of novel Au^I‐NHC compounds were developed with AIE characteristics. A complex with a PPh₃ ligand was selected out as it could achieve both prominent specific imaging of various cancer cells and efficient inhibition of their growth with negligible toxic effects on normal cells due to the targeting binding and strong inhibition towards thioredoxin reductase. This complex could also act as a powerful radiosensitizer to boost the anticancer efficacy with performance superior to that of popularly used auranofin. It holds great potential as a specific and effective theranostic drug in cancer diagnosis and precise therapy.

A spy in the RNA: The fluorescent nucleobase analogue 4‐cyanoindole was site‐specifically incorporated into the fluorogenic Chili RNA aptamer as a reporter for binding of several ligand classes. This first application of FRET between an isomorphic nucleobase donor and an intrinsically fluorogenic ligand revealed position‐dependent quantum yields and FRET efficiencies for mapping of the ligand binding site.

Abstract

RNA aptamers form compact tertiary structures and bind their ligands in specific binding sites. Fluorescence‐based strategies reveal information on structure and dynamics of RNA aptamers. Herein, we report the incorporation of the universal emissive nucleobase analog 4‐cyanoindole into the fluorogenic RNA aptamer Chili, and its application as a donor for supramolecular FRET to the bound ligands DMHBI⁺ or DMHBO⁺. The photophysical properties of the new nucleobase–ligand‐FRET pair revealed structural restraints for the overall RNA aptamer organization and identified nucleotide positions suitable for FRET‐based readout of ligand binding. This strategy is generally suitable for binding‐site mapping and may also be applied for responsive aptamer devices.

Organelle-specific nanocarriers (NCs) are highly sought after for delivering therapeutic agents into the cell nucleus. This necessitates nucleocytoplasmic transport (NCT) to bypass nuclear pore complexes (NPCs). However, little is known as to how comparably large NCs infiltrate this vital intracellular barrier to enter the nuclear interior. Here, we developed nuclear...

Cooperation without talking : An AIEgen/liquid crystal (LC) system with unique synergistic interactions was designed to pattern noninterference images (holographic and fluorescent) with unprecedented cooperative thermoresponse. The AIEgen's fluorescence intensity is controlled by the LC, while the LC's phase transition is in turn promoted by the AIEgen.

Abstract

Patterning multiple images within a single element without crosstalk can significantly increase the information capacity and security, but it is challenging to enable the response capability in each image. Now, the patterning of crosstalk‐free yet cooperative‐thermoresponse images (holographic and fluorescent images) is successfully achieved by designing a liquid crystal (LC)/AIEgen system with a unique synergy. The AIEgen's fluorescence intensity is controlled by the LC, while the LC's phase transition is in turn promoted by the AIEgen. The fluorescent image contrast is significantly boosted by efficient energy transfer (Φ _ET: 96 %) from the LC to the AIEgen. The AIEgen's photocyclization for fluorescent patterning occurs in a zero‐order kinetic manner and can be completed within several minutes when assisted by the LC. The photocyclization conversion is quantitatively dependent on the aggregation size: α ∼exp(‐d ), and able to reach as high as 98 %.

Nature Chemistry, Published online: 03 February 2020; doi:10.1038/s41557-019-0411-x

The structures of biologically active natural products have long served as inspiration in drug discovery. This Perspective outlines design principles and connectivity patterns for the de novo combination of natural product-derived fragments. The resulting ‘pseudo-natural products’ retain biological relevance yet exhibit structures and bioactivities not found in the natural products and their derivatives.

The MS2 system, with an MS2 binding site (MBS) and an MS2 coat protein fused to a fluorescent protein (MCP–FP), has been widely used to fluorescently label mRNA in live cells. However, one of its limitations is the constant background fluorescence signal generated from free MCP–FPs. To overcome this obstacle, we used a superfolder GFP (sfGFP) split into two or three nonfluorescent fragments that reassemble and emit fluorescence only when bound to the target mRNA. Using the high-affinity interactions of bacteriophage coat proteins with their corresponding RNA binding motifs, we showed that the nonfluorescent sfGFP fragments were successfully brought close to each other to reconstitute a complete sfGFP. Furthermore, real-time mRNA dynamics inside the nucleus as well as the cytoplasm were observed by using the split sfGFPs with the MS2–PP7 hybrid system. Our results demonstrate that the split sfGFP systems are useful tools for background-free imaging of mRNA with high spatiotemporal resolution.

Widely available proteins in nature are used to fabricate mechanically strong biological fibers through a facile microfluidic strategy. The crosslinking effect and double‐drawn treatment show a great influence on the mechanical performance of the resulting fibers. Furthermore, those biological fibers are successfully used for suturing skins and organs in different animal models.

Abstract

Lightweight and mechanically strong protein fibers are promising for many technical applications. Despite the widespread investigation of biological fibers based on spider silk and silkworm proteins, it remains a challenge to develop low‐cost proteins and convenient spinning technology for the fabrication of robust biological fibers. Since there are plenty of widely available proteins in nature, it is meaningful to investigate the preparation of fibers by the proteins and explore their biomedical applications. Here, a facile microfluidic strategy is developed for the scalable construction of biological fibers via a series of easily accessible spherical and linear proteins including chicken egg, quail egg, goose egg, bovine serum albumin, milk, and collagen. It is found that the crosslinking effect in microfluidic chips and double‐drawn treatment after spinning are crucial for the formation of fibers. Thus, high tensile strength and toughness are realized in the fibers, which are comparable or even higher than that of many recombinant spider silks or regenerated silkworm fibers. Moreover, the suturing applications in rat and minipig models are realized by employing the mechanically strong fibers. Therefore, this work opens a new direction for the production of biological fibers from natural sources.

Nature Chemistry, Published online: 29 January 2020; doi:10.1038/s41557-019-0392-9

Growing polymers directly on surfaces has emerged as a powerful tool because it can provide a route to otherwise inaccessible structures such as defect-free linear chains, graphene nanoribbons and two-dimensional networks. This Review Article describes general principles and key aspects of this method from the perspectives of surface science and polymer chemistry.

In this report, our work on the use of spin probes in the field of supramolecular chemistry and how electron spin resonance (EPR) has been used for detecting and identifying supramolecular assemblies is shortly reviewed

In this report, our work describing the use of spin probes in the field of supramolecular chemistry and how electron spin resonance (EPR) has been used for detecting and identifying supramolecular assemblies is shortly reviewed. Selected examples are reported, including paramagnetic host–guest complexes, self‐assembled systems doped with spin probes, spin‐labelled macrocycles and open shell mechanically interlocked structures (MIMs) such as rotaxanes, in which the dumbbell, the wheel or both are tagged with nitroxide radicals.

Nature Materials, Published online: 16 December 2019; doi:10.1038/s41563-019-0556-4

An n-type semiconducting polymer is used to realize an organic electrochemical transistor working as a glucose sensor and an all-polymer enzymatic biofuel cell able to power the sensor itself.

Nature Chemistry, Published online: 06 January 2020; doi:10.1038/s41557-019-0396-5

The mechanochemical activation of [4]-ladderane/ene has been studied and found to exhibit cascade unzipping and a consistent stereochemical distribution of products under various conditions and in different polymer backbones. Ab initio steered molecular dynamics simulations revealed unique non-equilibrium dynamic effects in the mechanochemistry of ladderane, cascade activation and reaction pathway bifurcation.

Nature, Published online: 18 December 2019; doi:10.1038/s41586-019-1809-8

Study of droplets containing nematic liquid crystal oligomers shows that a heterogeneous distribution of chain lengths plays a key part in driving reversible shape transformations with cooling and heating.

A DKR scenario towards O–P coupling reaction involving an easily accessible enantiopure phenol bearing a chiral sulfinyl auxiliary and racemic H‐phosphinates. The enantiopure P‐stereogenic phosphonates bearing two different alkoxy groups are valuable precursors to reach privileged ligands such as PAMPO.

Asymmetric synthesis of P‐stereogenic phosphonates presents a great challenge. Following this target we disclose herein a DKR strategy towards the O–P coupling reaction between an easily accessible enantiopure phenol bearing a chiral sulfinyl auxiliary and a commercially available or easily accessible racemic H‐phosphinate. Although moderate to high chiral induction is achieved, several diastereopure phosphonates can be afforded either by crystallization or flash chromatography. Thus accessed optically pure P‐stereogenic precursors may be used as appealing building blocks to rapidly assembly original privileged scaffolds as illustrated via the synthesis of a chiral ligand such as PAMPO.

Recent progress on the design and mechanical investigation of engineered protein‐based biomaterials is reviewed. As the two representative examples, the main discussion is of proteinaceous adhesives and fibers. The hierarchical structures of proteins have a great influence on the mechanical properties of relevant biomaterials. Perspectives and challenges in the field of functional proteins are also presented.

Abstract

Protein‐based structural biomaterials are of great interest for various applications because the sequence flexibility within the proteins may result in their improved mechanical and structural integrity and tunability. As the two representative examples, protein‐based adhesives and fibers have attracted tremendous attention. The typical protein adhesives, which are secreted by mussels, sandcastle worms, barnacles, and caddisfly larvae, exhibit robust underwater adhesion performance. In order to mimic the adhesion performance of these marine organisms, two main biological adhesives are presented, including genetically engineered protein‐based adhesives and biomimetic chemically synthetized adhesives. Moreover, various protein‐based fibers inspired by spider and silkworm proteins, collagen, elastin, and resilin are studied extensively. The achievements in synthesis and fabrication of structural biomaterials by DNA recombinant technology and chemical regeneration certainly will accelerate the explorations and applications of protein‐based adhesives and fibers in wound healing, tissue regeneration, drug delivery, biosensors, and other high‐tech applications. However, the mechanical properties of the biological structural materials still do not match those of natural systems. More efforts need to be devoted to the study of the interplay of the protein structure, cohesion and adhesion effects, fiber processing, and mechanical performance.

Aliphatic amines strongly coordinate, and therefore easily inhibit, the activity of transition-metal catalysts, posing a marked challenge to nitrogen-hydrogen (N–H) insertion reactions. Here, we report highly enantioselective carbene insertion into N–H bonds of aliphatic amines using two catalysts in tandem: an achiral copper complex and chiral amino-thiourea. Coordination by a homoscorpionate ligand protects the copper center that activates the carbene precursor. The chiral amino-thiourea catalyst then promotes enantioselective proton transfer to generate the stereocenter of the insertion product. This reaction couples a wide variety of diazo esters and amines to produce chiral α-alkyl α–amino acid derivatives.