Active‐Site Imprinting: Preparation of Fe–N–C Catalysts from Zinc Ion–Templated Ionothermal Nitrogen‐Doped Carbons

Atomically dispersed Fe–N–C catalysts are considered the most promising precious‐metal‐free alternative to state‐of‐the‐art Pt‐based oxygen reduction electrocatalysts for proton‐exchange membrane fuel cells. The exceptional progress in the field of research in the last ≈30 years is currently limited by the moderate active site density that can be obtained. Behind this stands the dilemma of metastability of the desired FeN₄ sites at the high temperatures that are believed to be a requirement for their formation. It is herein shown that Zn²⁺ ions can be utilized in the novel concept of active‐site imprinting based on a pyrolytic template ion reaction throughout the formation of nitrogen‐doped carbons. As obtained atomically dispersed Zn–N–Cs comprising ZnN₄ sites as well as metal‐free N₄ sites can be utilized for the coordination of Fe²⁺ and Fe³⁺ ions to form atomically dispersed Fe–N–C with Fe loadings as high as 3.12 wt%. The Fe–N–Cs are active electocatalysts for the oxygen reduction reaction in acidic media with an onset potential of E₀ = 0.85 V versus RHE in 0.1 m HClO₄. Identical location atomic resolution transmission electron microscopy imaging, as well as in situ electrochemical flow cell coupled to inductively coupled plasma mass spectrometry measurements, is employed to directly prove the concept of the active‐site imprinting approach.     

Optimal design of the Wilcoxon–Mann–Whitney‐test

In scientific research, many hypotheses relate to the comparison of two independent groups. Usually, it is of interest to use a design (i.e., the allocation of sample sizes m and n for fixed ) that maximizes the power of the applied statistical test. It is known that the two‐sample t‐tests for homogeneous and heterogeneous variances may lose substantial power when variances are unequal but equally large samples are used. We demonstrate that this is not the case for the nonparametric Wilcoxon–Mann–Whitney‐test, whose application in biometrical research fields is motivated by two examples from cancer research. We prove the optimality of the design in case of symmetric and identically shaped distributions using normal approximations and show that this design generally offers power only negligibly lower than the optimal design for a wide range of distributions.     

Fabrication of N‐doped Graphene–Carbon Nanotube Hybrids from Prussian Blue for Lithium–Sulfur Batteries

Hybrid nanostructures containing 1D carbon nanotubes and 2D graphene sheets have many promising applications due to their unique physical and chemical properties. In this study, the authors find Prussian blue (dehydrated sodium ferrocyanide) can be converted to N‐doped graphene–carbon nanotube hybrid materials through a simple one‐step pyrolysis process. Through field emission scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, Raman spectra, atomic force microscopy, and isothermal analyses, the authors identify that 2D graphene and 1D carbon nanotubes are bonded seamlessly during the growth stage. When used as the sulfur scaffold for lithium–sulfur batteries, it demonstrates outstanding electrochemical performance, including a high reversible capacity (1221 mA h g^?1 at 0.2 C rate), excellent rate capability (458 and 220 mA h g^?1 at 5 and 10 C rates, respectively), and excellent cycling stability (321 and 164 mA h g^?1 at 5 and 10 C (1 C = 1673 mA g^?1) after 1000 cycles). The enhancement of electrochemical performance can be attributed to the 3D architecture of the hybrid material, in which, additionally, the nitrogen doping generates defects and active sites for improved interfacial adsorption. Furthermore, the nitrogen doping enables the effective trapping of lithium polysulfides on electroactive sites within the cathode, leading to a much‐improved cycling performance. Therefore, the hybrid material functions as a redox shuttle to catenate and bind polysulfides, and convert them to insoluble lithium sulfide during reduction. The strategy reported in this paper could open a new avenue for low cost synthesis of N‐doped graphene–carbon nanotube hybrid materials for high performance lithium–sulfur batteries.     

Pollen S–locus F–box proteins of Petunia involved in S–RNase‐based self‐incompatibility are themselves subject to ubiquitin‐mediated degradation

Many flowering plants show self‐incompatibility, an intra‐specific reproductive barrier by which pistils reject self‐pollen to prevent inbreeding and accept non‐self pollen to promote out‐crossing. In Petunia, the polymorphic S–locus determines self/non‐self recognition. The locus contains a gene encoding an S–RNase, which controls pistil specificity, and multiple S‐locus F‐box (SLF) genes that collectively control pollen specificity. Each SLF is a component of an SCF (Skp1/Cullin/F‐box) complex that is responsible for mediating degradation of non‐self S‐RNase(s), with which the SLF interacts, via the ubiquitin–26S proteasome pathway. A complete set of SLFs is required to detoxify all non‐self S‐RNases to allow cross‐compatible pollination. Here, we show that SLF1 of Petunia inflata is itself subject to degradation via the ubiquitin–26S proteasome pathway, and identify an 18 amino acid sequence in the C‐terminal region of S₂‐SLF1 (SLF1 of S₂ haplotype) that contains a degradation motif. Seven of the 18 amino acids are conserved among all 17 SLF proteins of S₂ haplotype and S₃ haplotype involved in pollen specificity, suggesting that all SLF proteins are probably subject to similar degradation. Deleting the 18 amino acid sequence from S₂‐SLF1 stabilized the protein but abolished its function in self‐incompatibility, suggesting that dynamic cycling of SLF proteins is an integral part of their function in self‐incompatibility.     

nNOS–CAPON interaction mediates amyloid‐β‐induced neurotoxicity,especially in the early stages

In neurons, increased protein–protein interactions between neuronal nitric oxide synthase (nNOS) and its carboxy‐terminal PDZ ligand (CAPON) contribute to excitotoxicity and abnormal dendritic spine development, both of which are involved in the development of Alzheimer's disease. In models of Alzheimer's disease, increased nNOS–CAPON interaction was detected after treatment with amyloid‐β in vitro, and a similar change was found in the hippocampus of APP/PS1 mice (a transgenic mouse model of Alzheimer's disease), compared with age‐matched background mice in vivo. After blocking the nNOS–CAPON interaction, memory was rescued in 4‐month‐old APP/PS1 mice, and dendritic impairments were ameliorated both in vivo and in vitro. Furthermore, we demonstrated that S‐nitrosylation of Dexras1 and inhibition of the ERK–CREB–BDNF pathway might be downstream of the nNOS–CAPON interaction.     

Controllable Chain‐Length for Covalent Sulfur–Carbon Materials Enabling Stable and High‐Capacity Sodium Storage

Room temperature sodium–sulfur batteries have emerged as promising candidate for application in energy storage. However, the electrodes are usually obtained through infusing elemental sulfur into various carbon sources, and the precipitation of insoluble and irreversible sulfide species on the surface of carbon and sodium readily leads to continuous capacity degradation. Here, a novel strategy is demonstrated to prepare a covalent sulfur–carbon complex (SC‐BDSA) with high covalent‐sulfur concentration (40.1%) that relies on ? SO₃H (Benzenedisulfonic acid, BDSA) and SO₄^2? as the sulfur source rather than elemental sulfur. Most of the sulfur is exists in the form of O? S/C? S bridge‐bonds (short/long‐chain) whose features ensure sufficient interfacial contact and maintain high ionic/electronic conductivities of the sulfur–carbon cathode. Meanwhile, the carbon mesopores resulting from the thermal‐treated salt bath can confine a certain amount of sulfur and localize the diffluent polysulfides. Furthermore, the C? S_x? C bridges can be electrochemically broken at lower potential (<0.6 V vs Na/Na⁺) and then function as a capacity sponsor. And the R‐SO units can anchor the initially generated S_x^2? to form insoluble surface‐bound intermediates. Thus SC‐BDSA exhibits a specific capacity of 696 mAh g^?1 at 2500 mA g^?1 and excellent cycling stability for 1000 cycles with 0.035% capacity decay per cycle.     

Electron‐deficient p‐benzoyl‐l‐phenylalanine derivatives increase covalent chemical capture yields for protein–protein interactions

The photoactivatable amino acid p‐benzoyl‐l ‐phenylalanine (pBpa) has been used for the covalent capture of protein–protein interactions (PPIs) in vitro and in living cells. However, this technique often suffers from poor photocrosslinking yields due to the low reactivity of the active species. Here we demonstrate that the incorporation of halogenated pBpa analogs into proteins leads to increased crosslinking yields for protein–protein interactions. The analogs can be incorporated into live yeast and upon irradiation capture endogenous PPIs. Halogenated pBpas will extend the scope of PPIs that can be captured and expand the toolbox for mapping PPIs in their native environment.     

Super‐Stretchable Zinc–Air Batteries Based on an Alkaline‐Tolerant Dual‐Network Hydrogel Electrolyte

Stretchable devices need elastic hydrogel electrolyte as an essential component, while most hydrogels will lose their stretchability after being incorporated with strong alkaline solution. This is why highly stretchable zinc–air batteries have never been reported so far. Herein, super‐stretchable, flat‐ (800% stretchable) and fiber‐shaped (500% stretchable) zinc–air batteries are first developed by designing an alkaline‐tolerant dual‐network hydrogel electrolyte. In the dual‐network hydrogel electrolyte, sodium polyacrylate (PANa) chains contribute to the formation of soft domains and the carboxyl groups neutralized by hydroxyls as well as cellulose as potassium hydroxide stabilizer are responsible for vastly enhanced alkaline tolerance. The obtained super‐stretchable, flat zinc–air battery exhibits a high power density of 108.6 mW?cm^?2, increasing to 210.5 mW?cm^?2 upon being 800% stretched. Similar phenomena are observed for the 500% stretchable fiber‐shaped batteries. The devices can maintain stable power output even after being heavily deformed benefiting from the highly soft, alkaline‐tolerant hydrogel electrolyte developed. A bendable battery‐display system and water proof weavable fiber zinc–air battery are also demonstrated. This work will facilitate the progress of using zinc–air battery powering flexible electronics and smart clothes. Moreover, the developed alkaline‐tolerant super‐stretchable electrolyte can also be applied for many other alkaline electrolyte‐based energy storage/conversion devices.     

All‐Solid‐State Printed Bipolar Li–S Batteries

Despite their potential advantages over currently widespread lithium‐ion batteries, lithium–sulfur (Li–S) batteries are not yet in practical use. Here, for the first time bipolar all‐solid‐state Li–S batteries (ASSLSBs) are demonstrated that exhibit exceptional safety, flexibility, and aesthetics. The bipolar ASSLSBs are fabricated through a solvent‐drying‐free, ultraviolet curing‐assisted stepwise printing process at ambient conditions, without (high‐temperature/high‐pressure) sintering steps that are required for inorganic electrolyte‐based all‐solid‐state batteries. Two thermodynamically immiscible and nonflammable gel electrolytes based on ethyl methyl sulfone (EMS) and tetraethylene glycol dimethyl ether (TEGDME) are used to address longstanding concerns regarding the grain boundary resistance of conventional inorganic solid electrolytes, as well as the polysulfide shuttle effect in Li–S batteries. The EMS gel electrolytes embedded in the sulfur cathodes facilitate sulfur utilization, while the TEGDME gel composite electrolytes serve as polysulfide‐repelling separator membranes. Benefiting from the well‐designed cell components and printing‐driven facile processability, the resulting bipolar ASSLSBs exhibit unforeseen advancements in bipolar cell configuration, safety, foldability, and form factors, which lie far beyond those achievable with conventional Li–S battery technologies.     

Rechargeable Solid‐State Li–Air and Li–S Batteries: Materials,Construction, and Challenges

Nonaqueous Li–air and Li–S batteries are attracting considerable interest because of their outstanding theoretical capacities and energy densities. However, despite the substantial progress in their development, safety remains an issue because of the flammability of their organic electrolytes. Moreover, the electrolyte volatilization of Li–air batteries and “shuttle effect” in Li–S batteries seriously hinder their development. The use of solid‐state Li–air and Li–S batteries is one of the best solutions. Nevertheless, many challenges remain in solid electrolytes, electrodes, and interfaces. In this review, a comprehensive discussion on the development of solid‐state Li–air and Li–S batteries is provided. The discussion begins with introduction of the progress in solid electrolytes, including their ionic conductivities and chemical stabilities. It then moves on to the cathodes of both batteries and the interface between electrolytes and electrodes. The reaction process inside the cathode is also presented. Suggestions for the optimization of composite cathodes and modification of the electrode–electrolyte interface are provided in the end. Intensive effort is required for the development of solid‐state Li–air and Li–S batteries in the future.     

Determination of diethylstilbestrol based on biotin–streptavidin‐amplified time‐resolved fluoro‐immunoassay

A rapid and sensitive time‐resolved fluoroimmunoassay (TR–FIA) based on the biotin–streptavidin amplification system was developed for the determination of diethylstilbestrol (DES). Europium‐labelled streptavidin derivatives combined with europium and anhydride of diethylene triamine penta‐acetic acid were used to label streptavidin; biotin was coupled with goat anti‐rabbit IgG to form a biotin–goat anti‐rabbit IgG bridge between streptavidin–europium and the anti‐DES antibody in the immunoassay. The DES assay was carried out by measuring the fluorescence of Eu³⁺–SA at 615 nm. The presented method produced a wide linear range, 0.001–1000.0 ng/mL, and a detection limit up to 0.81 pg/mL for DES. The method was applied to determine DES in serum samples, with recoveries of 97.4–107.8% and RSD 1.32–4.04%. The assay results by the present method showed that biotin–streptavidin amplified TR–FIA for DES detection; it may offer high sensitivity and promising alternative special methods in biological samples. Copyright © 2011 John Wiley & Sons, Ltd.     

Flexible and High‐Loading Lithium–Sulfur Batteries Enabled by Integrated Three‐In‐One Fibrous Membranes

Lithium–sulfur batteries are appealing as high‐energy storage systems and hold great application prospects in wearable and portable electronics. However, severe shuttle effects, low sulfur conductivity, and especially poor electrode mechanical flexibility restrict sulfur utilization and loading for practical applications. Herein, high‐flux, flexible, electrospun fibrous membranes are developed, which succeed in integrating three functional units (cathode, interlayer, and separator) into an efficient composite. This structure helps to eliminate negative interface effects, and effectively drives synergistic boosts to polysulfide confinement, electron transfer, and lithium‐ion diffusion. It delivers a high initial capacity of 1501 mA h g^?1 and a discharge capacity of 933 mA h g^?1 after 400 cycles, with slow capacity attenuation (0.069% per cycle). Even under high sulfur loading (13.2 mg cm^?2, electrolyte/sulfur ratio = 6 mL g^?1) or in an alternative folded state, this three‐in‐one membrane still exhibits high areal capacity (11.4 mA h cm^?2) and exceptional application performance (powering an array of over 30 light‐emitting diodes (LEDs)), highlighting its huge potential in high‐energy flexible devices.     

Constructing thioether‐tethered cyclic peptides via on‐resin intra‐molecular thiol–ene reaction

Thiol–ene reactions have been used in a variety of applications that mostly involve an inter‐molecular pathway. Herein, we report a facile method to construct thioether‐tethered cyclic peptides via an intra‐molecular thiol–ene reaction. This reaction is efficient, selective, and has good residue compatibility. Short peptides with thioether tethers were constructed and were used to construct longer cyclic peptides. This synthetic method may be useful for constructing bioactive peptides. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.