Peptides derived from dietary proteins, have been reported to display significant antioxidant activity, which may exert notably beneficial effects in promoting human health and in food processing. ...Recently, much research has focused on the generation, separation, purification and identification of novel peptides from various protein sources. Some researchers have tried to discover the structural characteristics of antioxidant peptides in order to lessen or avoid the tedious and aimless work involving the ongoing generated peptide preparation schemes. This review aims to summarize the current knowledge on the relationship between the structural features of peptides and their antioxidant activities. The relationship between the structure of the precursor proteins and their abilities to release antioxidant fragments will also be summarized and inferred. The preparation methods and antioxidant capacity evaluation assays of peptides and a prediction scheme of quantitative structure-activity relationship (QSAR) will also be pointed out and discussed.
In this paper, we propose a switchable bi-functional metamaterial device based on a hybrid gold-vanadium dioxide (VO
) nanostructure. Utilizing the property of a metal-to-insulator transition in VO
, ...perfect absorption and asymmetric transmission (AT) can be thermally switched for circularly polarized light in the near-infrared region. When VO
is in the metallic state, the designed metamaterial device behaves as a chiral-selective plasmonic perfect absorber, which can result in an optical circular dichroism (CD) response with a maximum value ∼ 0.7. When VO
is in the insulating state, the proposed metamaterial device exhibits a dual-band AT effect. The combined hybridization model and electromagnetic field distributions are presented to explain the physical mechanisms of chiral-selective perfect absorption and AT effect, respectively. The influences of structure parameters on CD response and AT effect are also discussed. Moreover, the proposed switchable bi-functional device is robust against the incident angle for obtaining perfect absorption and strong CD response as well as the AT effect. Our work may provide a promising path for the development of multifunctional optoelectronic devices, such as thermal emitters, optical modulators, CD spectroscopy, optical isolator, etc.
Abstract
Recently developed solid-state catalysts can mediate carbon dioxide (CO
2
) electroreduction to valuable products at high rates and selectivities. However, under commercially relevant ...current densities of > 200 milliamperes per square centimeter (mA cm
−2
), catalysts often undergo particle agglomeration, active-phase change, and/or element dissolution, making the long-term operational stability a considerable challenge. Here we report an indium sulfide catalyst that is stabilized by adding zinc in the structure and shows dramatically improved stability. The obtained ZnIn
2
S
4
catalyst can reduce CO
2
to formate with 99.3% Faradaic efficiency at 300 mA cm
−2
over 60 h of continuous operation without decay. By contrast, similarly synthesized indium sulfide without zinc participation deteriorates quickly under the same conditions. Combining experimental and theoretical studies, we unveil that the introduction of zinc largely enhances the covalency of In-S bonds, which “locks” sulfur—a catalytic site that can activate H
2
O to react with CO
2
, yielding HCOO* intermediates—from being dissolved during high-rate electrolysis.
In Earth's low atmosphere, hurricanes are destructive due to their great size, strong spiral winds with shears, and intense rain/precipitation. However, disturbances resembling hurricanes have not ...been detected in Earth's upper atmosphere. Here, we report a long-lasting space hurricane in the polar ionosphere and magnetosphere during low solar and otherwise low geomagnetic activity. This hurricane shows strong circular horizontal plasma flow with shears, a nearly zero-flow center, and a coincident cyclone-shaped aurora caused by strong electron precipitation associated with intense upward magnetic field-aligned currents. Near the center, precipitating electrons were substantially accelerated to ~10 keV. The hurricane imparted large energy and momentum deposition into the ionosphere despite otherwise extremely quiet conditions. The observations and simulations reveal that the space hurricane is generated by steady high-latitude lobe magnetic reconnection and current continuity during a several hour period of northward interplanetary magnetic field and very low solar wind density and speed.
•SrCS/SF blend membrane containing microporous structure was developed.•The introduction of SrCS into SF membrane facilitates osteoblasts proliferation.•SrCS/SF membrane has positive ...osteoimmunomodulatory effects.
A membrane used for guided bone regeneration (GBR) serves as a bioactive compartment rather than a physical barrier. However, the pure membrane may not provide an optimal microenvironment for bone formation and remodeling. Here, a novel strontium chondroitin sulfate/silk fibroin (SrCS/SF) blend membrane containing microporous structure was fabricated. By increasing incorporation content of SrCS, SrCS/SF membranes exhibit better mechanical properties and higher water retention capacity. In vitro results reveal that higher content of SrCS membranes facilitate osteoblasts proliferation. The evaluation of the osteoimmunomodulatory effects of the membranes reveals that SrCS/SF membranes should have positive effects on modulating the osteoimmune response of macrophages, by downregulating the expression of pro-inflammatory cytokines and the expression of degradation related catabolic genes and upregulating osteogenic factors. It is therefore believed that the developed SrCS/SF membranes should be potentially used as multifunctional bioactive GBR membranes.
Abstract
Delving into the influence of strain on organic reactions in small molecules at the molecular level can unveil valuable insight into developing innovative synthetic strategies and ...structuring molecules with superior properties. Herein, we present a molecular‐strain engineering approach to facilitate the consecutive 1,2‐aryl shift (formal 1,3‐aryl shift) in molecular bows (MBs) that integrate 1,4‐dimethoxy‐2,5‐cyclohexadiene moieties. By introducing ring strain into MBs through tethering the bow limb, we can harness the intrinsic mechanical forces to drive multistep aryl shifts from the
para‐
to the
meta‐
to the
ortho‐
position. Through the use of precise intramolecular strain, the seemingly impractical 1,3‐aryl shift was realized, resulting in the formation of
ortho‐
disubstituted products. The solvent and temperature play a crucial role in the occurrence of the 1,3‐aryl shift. The free energy calculations with inclusion of solvation support a feasible mechanism, which entails multistep carbocation rearrangements, for the formal 1,3‐aryl shift. By exploring the application of molecular strain in synthetic chemistry, this research offers a promising direction for developing new tools and strategies towards precision organic synthesis.
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•B doped and O vacancy-rich Co3O4 was obtained by alternate Co salt and NaBH4 reaction.•VOB-Co3O4/NF exhibits excellent catalytic activities for both OER and HER process.•VOB-Co3O4/NF ...leads to superb hydrolytic dehydrogenation of alkaline NaBH4 solution.•Incorporation of oxygen vacancies brings about superior electronic structure.
Developing earth abundant electrocatalyst is imperative to large-scale hydrogen production for transforming current fossil fuel-based economy into future renewable energy economy. In this paper, we report the synthesis of self-supported VOB-Co3O4/NF nanowire arrays directly grown on Ni foam, which can serve as a trifunctional catalyst for producing hydrogen and oxygen by electrolyzing water in alkaline media or producing hydrogen via hydrolyzing alkaline NaBH4 solution. The engineered boron and oxygen defects in Co3O4 nanowires prove to effectively modulate their electronic structure leading to the increased electrical conductivity and create a large quantity of electroactive sites. The resulting self-supported VOB-Co3O4/NF electrode delivers a current density of 50 mA cm−2 at overpotentials of 184 mV for hydrogen evolution reaction (HER) and 315 mV for oxygen evolution reaction (OER) in 1.0 M KOH with excellent stability and durability. The VOB-Co3O4/NF as both cathode and anode requires 1.67 V to achieve a current density of 10 mA cm−2 for overall water splitting reaction. Besides, VOB-Co3O4/NF presents much higher hydrogen generation rate (HGR) of 7055 mL min−1 gcatalyst−1 with activation energy (Ea) of ca. 29.7 kJ mol−1. for hydrolytic dehydrogenation of alkaline NaBH4 solution, outperforming most of the reported non-noble metal-based catalysts and even precious metal catalysts.
We report here the one‐pot synthesis of benzo1,2‐a : 3,4‐a′ : 5,6‐a′′triazulene (BTA), wherein three azulene units are embedded through a tandem reaction comprising two steps, Suzuki coupling and ...Knoevenagel condensation, between a readily available triborylated truxene precursor and 8‐bromo‐1‐naphthaldehyde. Its nitration leads to a regioselective trinitrated product, namely, BTA‐NO2. Single‐crystal X‐ray crystallography revealed that the superstructure of BTA consists of a dimer stacked by two enantiomeric helicene conformers, while that of BTA‐NO2 consists of an unprecedented π‐tetramer stacked from two enantiomeric dimers, that is, four distinct helicene conformers. Both compounds show excellent stability and fluorescence with large Stokes shifts of up to 5100 cm−1. In addition, BTA‐NO2 exhibits a unique solvatochromic effect in different solvents and hydrogen‐bonding‐induced emission transfer in different ratios of THF/H2O solutions.
A C3‐symmetrical truxene‐based benzotriazulene derivative with three embedded azulene units was concisely synthesized by means of a cascade 4+3 annulation involving a Suzuki coupling followed by Knoevenagel condensation of a readily available triborylated truxene precursor and 8‐bromo‐1‐naphthaldehyde. The regioselectively trinitrated product exhibits a large Stokes shift of up to 5100 cm−1 along with unique solvatochromic effects in different solvents.
A modular approach to azulene building blocks was developed starting from readily available aryl‐substituted cyclopentadiene and ortho‐haloaryl aldehyde by dehydration condensation followed by ...palladium‐catalyzed C−H coupling. It facilitates the synthesis of four nonalternant isomers of pentacene and hexacene, namely, dibenzoe,gazulene, benzo1,2‐f : 5,4‐f′diazulene, benzo1,2‐f : 4,5‐f′diazulene, and naphtho2,3‐f : 6,7‐f′diazulene, which exhibit narrow band gaps with high stability in addition to protonation‐caused enhanced near‐infrared fluorescence. We discovered that in these isomers, i) constitutional isomerism influences significantly their photoelectric properties and ii) the elongation of the conjugation system does not necessarily lead to a narrowing in the band gap. Due to the easy modifiability of the nonazulene building blocks, this strategy can be extended to modularly prepare numerous multiazulene‐fused aromatics.
A modular two‐step 4+3 annulation approach to azulene units was developed starting from readily available aryl‐substituted cyclopentadiene and ortho‐haloaryl aldehyde by dehydration condensation followed by palladium‐catalyzed C−H coupling. It facilitates the syntheses of four nonalternant isomers of pentacene and hexacene including DBA, BDA1, BDA2, and NDA which exhibit narrow band gaps and protonation‐caused enhanced near‐infrared emission.
Titanium (Ti) and its alloys are the most widely used materials for biomedical applications, owing to their good corrosion resistance, mechanical properties, and biocompatibility. However, their ...long-term performance is compromised by the post-surgery complications such as implant-associated infection and mechanical loosening. Surface modification can be adopted to alleviate these concerns while preserving the desirable bulk attributes. Among various techniques, electrochemical methods offer merits such as mild processing conditions, non-line-of-sight operation, low cost, as well as large-scale production. This paper gives a brief overview of surface engineering of the Ti-based alloys from the perspective of electrochemistry. It mainly focuses on three major electrochemical techniques: low voltage anodization, micro-arc oxidation, and electrodeposition. Overall, effects have been made to bring out a comprehensive understanding of electrochemical modification of Ti-based alloys for biomedical applications.
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![Strain‐Driven Formal [1,3]‐...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1433-7851/small "Strain‐Driven Formal [1,3]‐Aryl Shift within Molecular Bows")
