“Graphitic” (g)‐C3N4 with a layered structure has the potential of forming graphene‐like nanosheets with unusual physicochemical properties due to weak van der Waals forces between layers. Herein is ...shown that g‐C3N4 nanosheets with a thickness of around 2 nm can be easily obtained by a simple top‐down strategy, namely, thermal oxidation etching of bulk g‐C3N4 in air. Compared to the bulk g‐C3N4, the highly anisotropic 2D‐nanosheets possess a high specific surface area of 306 m2 g−1, a larger bandgap (by 0.2 eV), improved electron transport ability along the in‐plane direction, and increased lifetime of photoexcited charge carriers because of the quantum confinement effect. As a consequence, the photocatalytic activities of g‐C3N4 nanosheets have been remarkably improved in terms of •OH radical generation and photocatalytic hydrogen evolution.
Graphene‐like C3N4 nanosheets produced by direct thermal oxidative etching of bulk “graphitic”‐C3N4 show superior photocatalytic activities compared to the bulk due to a high specific surface area, a larger bandgap (by 0.2 eV), increased lifetimes of photoexcited charge carriers, and improved electron transport ability.
Thermal processing is required for a variety of products and remains a problem for whey proteins that undergo denaturation and aggregation above the denaturation temperature. This causes challenges ...to maintain clarity and dispersibility of protein dispersions, particularly at acidity near the isoelectric point of the protein and increased ionic strength. This work reports for the first time that glycation of whey protein with a sufficient number of maltodextrins prevented protein aggregation before and after heating at 88 °C for 2 min at pH 3.0–7.0 and 0–150 mM NaCl or CaCl2. The mechanism of maintaining protein dispersion clarity during heating was illustrated by several complementary analytical techniques that elucidated primary, secondary, and tertiary structures, as well as thermal denaturation and surface charge properties of glycated whey proteins. Steric hindrance was concluded to be the major mechanism responsible for transparent dispersions with protein structures smaller than 12 nm after heating.
The oxygen reduction reaction (ORR) is one of the most important reactions in life processes and energy conversion systems. To alleviate global warming and the energy crisis, the development of ...high‐performance electrocatalysts for the ORR for application in energy conversion and storage devices such as metal–air batteries and fuel cells is highly desirable. Inspired by the biological oxygen activation/reduction process associated with heme‐ and multicopper‐containing metalloenzymes, iron and copper‐based transition‐metal complexes have been extensively explored as ORR electrocatalysts. Herein, an outline into recent progress on non‐precious‐metal electrocatalysts for the ORR is provided; these electrocatalysts do not require pyrolysis treatment, which is regarded as desirable from the viewpoint of bioinspired molecular catalyst design, focusing on iron/cobalt macrocycles (porphyrins, phthalocyanines, and corroles) and copper complexes in which the ORR activity is tuned by ligand variation/substitution, the method of catalyst immobilization, and the underlying supporting materials. Current challenges and exciting imminent developments in bioinspired ORR electrocatalysts are summarized and proposed.
An outline of recent progress on non‐precious‐metal electrocatalysts for the oxygen reduction reaction (ORR) is presented from the viewpoint of bioinspired molecular catalyst design, with a focus on iron/cobalt macrocycles and copper complexes in which the ORR activity is tuned by ligand modification, the method of catalyst immobilization, and the underlying supporting materials (see scheme).
Necroptosis is a form of regulated necrosis and is executed by MLKL when MLKL is engaged in triggering the rupture of cell plasma membrane. MLKL activation also leads to the protease, ADAMs-mediated ...ectodomain shedding of cell surface proteins of necroptotic cells. Tumor necroptosis often happens in advanced solid tumors, and blocking necroptosis by MLKL deletion in breast cancer dramatically reduces tumor metastasis. It has been suggested that tumor necroptosis affects tumor progression through modulating the tumor microenvironment. However, the exact mechanism by which tumor necroptosis promotes tumor metastasis remains elusive. Here, we report that the ectodomain shedding of cell surface proteins of necroptotic cells is critical for the promoting effect of tumor necroptosis in tumor metastasis through inhibiting the anti-tumor activity of T cells. We found that blocking tumor necroptosis by MLKL deletion led to the dramatic reduction of tumor metastasis and significantly elevated anti-tumor activity of tumor-infiltrating and peripheral blood T cells. Importantly, the increased anti-tumor activity of T cells is a key cause for the reduced metastasis as the depletion of CD8+ T cells completely restored the level of metastasis in the Mlkl KO mice. Interestingly, the levels of some soluble cell surface proteins including sE-cadherin that are known to promote metastasis are also dramatically reduced in MLKL null tumors/mice. Administration of ADAMs pan inhibitor reduces the levels of soluble cell surface proteins in WT tumors/mice and leads to the dramatic decrease in metastasis. Finally, we showed the sE-cadherin/KLRG1 inhibitory receptor is the major pathway for necroptosis-mediated suppression of the anti-tumor activity of T cells and the promotion of metastasis. Hence, our study reveals a novel mechanism of tumor necroptosis-mediated promotion of metastasis and suggests that tumor necroptosis and necroptosis-activated ADAMs are potential targets for controlling metastasis.
The therapeutic potential of mesenchymal stem/stromal cells (MSCs) is limited by acquired senescence following prolonged culture expansion and high-passage numbers. However, the degree of cell ...senescence is dynamic, and cell-cell communication is critical to promote cell survival. MSC spheroids exhibit improved viability compared with monodispersed cells, and actin-rich tunneling nanotubes (TNTs) may mediate cell survival and other functions through the exchange of cytoplasmic components. Building upon our previous demonstration of TNTs bridging MSCs within these cell aggregates, we hypothesized that TNTs would influence the expression of senescence markers in MSC spheroids. We confirmed the existence of functional TNTs in MSC spheroids formed from low-passage, high-passage, and mixtures of low- and high-passage cells using scanning electron microscopy, confocal microscopy, and flow cytometry. The contribution of TNTs toward the expression of senescence markers was investigated by blocking TNT formation with cytochalasin D (CytoD), an inhibitor of actin polymerization. CytoD-treated spheroids exhibited decreases in cytosol transfer. Compared with spheroids formed solely of high-passage MSCs, the addition of low-passage MSCs reduced p16 expression, a known genetic marker of senescence. We observed a significant increase in p16 expression in high-passage cells when TNT formation was inhibited, establishing the importance of TNTs in MSC spheroids. These data confirm the restorative role of TNTs within MSC spheroids formed with low- and high-passage cells and represent an exciting approach to use higher-passage cells in cell-based therapies.
Although biomimetic designs are expected to play a key role in exploring future structural materials, facile fabrication of bulk biomimetic materials under ambient conditions remains a major ...challenge. Here, we describe a mesoscale "assembly-and-mineralization" approach inspired by the natural process in mollusks to fabricate bulk synthetic nacre that highly resembles both the chemical composition and the hierarchical structure of natural nacre. The millimeter-thick synthetic nacre consists of alternating organic layers and aragonite platelet layers (91 weight percent) and exhibits good ultimate strength and fracture toughness. This predesigned matrix-directed mineralization method represents a rational strategy for the preparation of robust composite materials with hierarchically ordered structures, where various constituents are adaptable, including brittle and heat-labile materials.
Vacancy defects can play an important role in modifying the electronic structure and the properties of photoexcited charge carriers and consequently the photocatalytic activity of semiconductor ...photocatalysts. By controlling the polycondensation temperature of a dicyandiamide precursor in the preparation of graphitic carbon nitride (g-C3N4), we introduced nitrogen vacancies in the framework of g-C3N4. These vacancies exert remarkable effects on modifying the electronic structure of g-C3N4 as shown in UV–visible absorption spectra and valence band spectra. Steady and time-resolved fluorescence emission spectra show that, due to the existence of abundant nitrogen vacancies, the intrinsic radiative recombination of electrons and holes in g-C3N4 is greatly restrained, and the population of short-lived and long-lived charge carriers is decreased and increased, respectively. As a consequence, the overall photocatalytic activity of the g-C3N4, characterized by the ability to generate •OH radicals, photodecomposition of Rhodamine B, and photocatalytic hydrogen evolution under both UV–visible and visible light, was remarkably improved.
Two colorless and transparent polyimide (CPI) films with enhanced high‐temperature dimensional stability and solution‐processability were prepared from the methyl‐substituted benzanilide containing ...organo‐soluble polyimide (PI) resins. For this target, a new aromatic diamine, 2,3′‐dimethyl‐4,4′‐diaminobenzanilide (MMDABA) was synthesized. The methyl substituents were expected to endow the derived PI resins good solubility and rigid‐rod benzanilide units can efficiently reduce the coefficients of thermal expansion (CTE) of the derived CPI films. CPI‐a and CPI‐b were prepared by the one‐step thermal polycondensation from MMDABA with hydrogenated pyromellitic dianhydride for CPI‐a and hydrogenated 3,3′,4,4′‐biphenyltetracarboxylic dianhydride for CPI‐b, respectively. The derived PI resins were soluble in polar aprotic solvents. Colorless and transparent CPI‐a and CPI‐b films were prepared from the PI solutions and the subsequent 280°C curing. The CPI films showed good transparency in visible light and transmittances higher than 80% at 450 nm and yellowness index (b*) below 2.0. More importantly, the derived CPI‐a film showed the glass transition temperature (Tg) of 417.5°C and the CTE value of 46.9 × 10−6/K in the range of 50–250°C. Apparently, incorporation of alkyl‐substituted benzanilide units achieved good balance among solution‐processability, high‐temperature dimensional stability, and optical properties.
The gut microbiota influences the health of the host, especially with regard to gut immune homeostasis and the intestinal immune response. In addition to serving as a nutrient enhancer, L-tryptophan ...(Trp) plays crucial roles in the balance between intestinal immune tolerance and gut microbiota maintenance. Recent discoveries have underscored that changes in the microbiota modulate the host immune system by modulating Trp metabolism. Moreover, Trp, endogenous Trp metabolites (kynurenines, serotonin, and melatonin), and bacterial Trp metabolites (indole, indolic acid, skatole, and tryptamine) have profound effects on gut microbial composition, microbial metabolism, the host's immune system, the host-microbiome interface, and host immune system-intestinal microbiota interactions. The aryl hydrocarbon receptor (AhR) mediates the regulation of intestinal immunity by Trp metabolites (as ligands of AhR), which is beneficial for immune homeostasis. Among Trp metabolites, AhR ligands consist of endogenous metabolites, including kynurenine, kynurenic acid, xanthurenic acid, and cinnabarinic acid, and bacterial metabolites, including indole, indole propionic acid, indole acetic acid, skatole, and tryptamine. Additional factors, such as aging, stress, probiotics, and diseases (spondyloarthritis, irritable bowel syndrome, inflammatory bowel disease, colorectal cancer), which are associated with variability in Trp metabolism, can influence Trp-microbiome-immune system interactions in the gut and also play roles in regulating gut immunity. This review clarifies how the gut microbiota regulates Trp metabolism and identifies the underlying molecular mechanisms of these interactions. Increased mechanistic insight into how the microbiota modulates the intestinal immune system through Trp metabolism may allow for the identification of innovative microbiota-based diagnostics, as well as appropriate nutritional supplementation of Trp to prevent or alleviate intestinal inflammation. Moreover, this review provides new insight regarding the influence of the gut microbiota on Trp metabolism. Additional comprehensive analyses of targeted Trp metabolites (including endogenous and bacterial metabolites) are essential for experimental preciseness, as the influence of the gut microbiota cannot be neglected, and may explain contradictory results in the literature.
PDF
