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Topic review
Updated time: 01 Jul 2021
Definition: Increased airway wall thickness and remodeling of bronchial mucosa are characteristic of asthma and may arise from altered integrin signaling on airway cells. Here, we analyzed the expression of β1-subfamily integrins on blood and airway cells (flow cytometry), inflammatory biomarkers in serum and bronchoalveolar lavage, reticular basement membrane (RBM) thickness and collagen deposits in the mucosa (histology), and airway geometry (CT-imaging) in 92 asthma patients (persistent airflow limitation subtype: n=47) and 36 controls. Persistent airflow limitation was associated with type-2 inflammation, elevated soluble α2 integrin chain, and changes in the bronchial wall geometry. Both subtypes of asthma showed thicker RBM than control, but collagen deposition and epithelial α1 and α2 integrins staining were similar. Type-I collagen accumulation and RBM thickness were inversely related to the epithelial expression of the α2 integrin chain. Expression of α2β1 integrin on T-cells and eosinophils was not altered in asthma. Collagen I deposits were, however, more abundant in patients with lower α2β1 integrin on blood and airway CD8+ T-cells. Thicker airway walls in CT were associated with lower α2 integrin chain on blood CD4+ T-cells and airway eosinophils. Our data suggest that α2β1 integrin on inflammatory and epithelial cells may protect against airway remodeling advancement in asthma.
Entry Collection : Chemical Bond
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Topic review
Updated time: 17 Jun 2021
Submitted by: samy shaban
Definition: Recently, aptamers have attracted attention in the biosensing field as signal recognition elements because of their high binding affinity toward specific targets such as proteins, cells, small molecules, and even metal ions. Aptamers have intrinsic advantages, such as their availability for both chemical modifications and conjugation with different labels, facilitating their ability to be used to construct a sensitive and highly selective platform sensor. Aptamers can be easily functionalized and engineered, providing several signaling modes such as colorimetric, fluorometric, and electrochemical, in what is known as aptasensors.
Entry Collection : Chemical Bond
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Topic review
Updated time: 18 May 2021
Submitted by: Alexandru C. Razus
Definition: The nonalternant aromatic azulene, an isomer of alternant naphthalene, differs from the latter in peculiar properties. The large polarization of the π-electron system over the seven and five rings gives to azulene electrophile property a pronounced tendency to donate electrons to an acceptor, substituted at azulene 1 position. This paper presents cases in which azulene transfers electrons to a suitable acceptor as methylium ions, positive charged heteroaromatics and examples of neutral molecules that can accept electrons.
Entry Collection : Chemical Bond
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Topic review
Updated time: 18 Dec 2020
Submitted by: Pierina Visciano
Definition: The occurrence of biogenic amines in fish is directly associated with microorganisms withdecarboxylase activity. These compounds are generally detoxified by oxidases in the intestinal tract ofhumans, but some conditions, such as alcohol consumption, enzyme deficiency, or monoamino-oxidaseantidepressant use, can make their intake by food dangerous. Due to its toxicity, histamine is a uniquebiogenic amine with regulatory limits for fishery products. This review focuses on biogenic amines infish, with a detailed picture of the number of alert notifications or intoxication events reported in thelast years. The favoring conditions for their formation, as well as the main preventive and controlmeasures to ensure public health, are also reviewed.
Entry Collection : Chemical Bond
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Topic review
Updated time: 17 Jun 2021
Submitted by: Stoyan Nihtianov
Definition: The discovery of the extremely shallow amorphous boron-crystalline silicon heterojunction occurred during the development of highly sensitive, hard and robust detectors for low-penetration-depth ionizing radiation, such as ultraviolet photons and low-energy electrons (below 1 keV). For many years it was believed that the junction created by the chemical vapor deposition of amorphous boron on n-type crystalline silicon was a shallow p-n junction, although experimental results could not provide evidence for such a conclusion. Only recently, quantum-mechanics based modelling revealed the unique nature and the formation mechanism of this new junction. Here, the entry reviews the initiation and the history of understanding the a-B/c-Si interface (henceforth called the “boron-silicon junction”).
Entry Collection : Chemical Bond
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Topic review
Updated time: 24 Nov 2020
Submitted by: Wei Chen
Definition: Using renewable energy to convert CO2 to a clean fuel ethanol can not only reduce carbon emission by the utilization of CO2 as feedstock, but also store renewable energy as the widely used chemical and high-energy-density fuel, being considered as a perfect strategy to address current environment and energy issues. Developing efficient electrocatalysts, photocatalysts, and photoelectrocatalysts for CO2 reduction is the most crucial keystone for achieving this goal. Considerable progresses in CO2-based ethanol production have been made over the past decades. This review provides the general principles and summarizes the latest advancements of electrocatalytic, photocatalytic and photoelectrocatalytic CO2 conversion to ethanol. Furthermore, the main challenges and proposed future prospects are illustrated for further development of the clean fuel ethanol production.
Entry Collection : Chemical Bond
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Topic review
Updated time: 17 Jun 2021
Submitted by: Albert Rimola
Definition: The main objective of computational chemistry is to solve chemical problems by simulating chemical systems (molecular, biological, materials) in order to provide reliable, accurate and comprehensive information at an atomic level. To this end, there are two main methodological families: those based on quantum chemical methods and those based on molecular mechanics. The former are methods in which the electrons are explicitly accounted for, while in the latter their presence is hidden in the force field.
Entry Collection : Chemical Bond
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Topic review
Updated time: 21 Jun 2021
Submitted by: SHERIFF BALOGUN
Definition: Potassium bromate (KBrO3), a renowned oxidizing agent, has a huge reputation for being one of the best and least expensive dough-improving substances in the baking industry. As such, its importance in the baking industry cannot be overemphasized. KBrO3 produced the desired result in baking by influencing the physical and chemical properties of macromolecules such as protein and starch often found in the dough. Precisely, the viscosity, extent of gelatinization, swelling characteristics of the dough, and disulfide linkage formation (in gluten proteins) are affected by the use of KBrO3 as an additive in bread baking. Bromate has been found to be a product of water treatment due to bromide ion oxidation that occurs during ozonation.
Entry Collection : Chemical Bond
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Topic review
Updated time: 15 Apr 2021
Definition: The crucial role played by compounds bearing amide functions, not only in biological processes but also in several fields of chemistry, life polymers and material sciences, has brought about many significant discoveries and innovative approaches for their chemical synthesis. Within this context, and following the development of C-H functionalization strategies, C-H amidation reactions have only recently emerged as valuable approaches for the construction of amide functions. These methodologies have been successfully used for both C(sp2)- and C(sp3)-H activations and blossoming synthetic applications have appeared in the last two years (2019-2020 timeframe).
Entry Collection : Chemical Bond
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Topic review
Updated time: 17 Jun 2021
Submitted by: Diego F. Gomez-Casati
Definition: Iron and sulfur are two essential elements for all organisms. These elements form the Fe-S clusters that are present as cofactors in numerous proteins and protein complexes related to key processes in cells, such as respiration and photosynthesis, and participate in numerous enzymatic reactions.
Entry Collection : Chemical Bond
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