Search

Ergothioneine (EGT) is a rare thiohistidine derivative with exceptional antioxidant properties. The blood level of EGT is considered highly reliable predictors for cardiovascular diseases and mortality, yet animals lack the ability to synthesize this compound. Free plasmids have been previously used to overexpress genes involved in the EGT biosynthetic pathway of Mycolicibacterium neoaurum. Here, we tentatively introduced a putative transporter gene mfsT1 into high‐copy plasmids and sharply increased the ratio of extracellular EGT concentration from 18.7% to 44.9%. Subsequently, an additional copy of egtABCDE, hisG, and mfsT1 was inserted into the genome with a site‐specific genomic integration tool of M. neoaurum, leading a 2.7 times increase in EGT production. Co‐enhancing the S‐adenosyl‐L‐methionine regeneration pathway, or alternatively, the integration of three copies of egtABCDE, hisG and mfsT1 into the genome further increased the total EGT yield by 16.1% (64.6 mg/L) and 21.7% (67.7 mg/L), respectively. After 168‐h cultivation, the highest titer reached 85.9 mg/L in the latter strain with three inserted copies. This study provided a solid foundation for genome engineering to increase the production of EGT in M. neoaurum. [ABSTRACT FROM AUTHOR]

Chronic cerebral hypoperfusion‐derived brain damage contributes to the progression of vascular cognitive impairment and dementia (VCID). Cumulative evidence has shown that microRNAs (miRs) are emerging as novel therapeutic targets for CNS disorders. In this study, it is sought to determine the regulatory role of miR‐15a/16‐1 in VCID. It is found that miR‐15a/16‐1 knockout (KO) mice exhibit less cognitive and sensorimotor deficits following VCID. Genetic deficiency of miR‐15a/16‐1 in VCID mice also mitigate myelin degeneration, axonal injury, and neuronal loss. Mechanistically, miR‐15a/16‐1 binds to the 3'‐UTR of AKT3 and IL‐10RA. Genetic deletion of miR‐15a/16‐1 increases AKT3 and IL‐10RA expression in VCID brains, and intranasal delivery of AKT3 and IL‐10RA siRNA‐loaded nanoparticles partially reduce brain protection and cognitive recovery in miR‐15a/16‐1 KO mice after VCID. In conclusion, the miR‐15a/16‐1‐IL/10RA/AKT3 axis plays a critical role in regulating vascular brain damage and cognitive decline after VCID. Targeting miR‐15a/16‐1 is a novel therapeutic approach for the treatment of VCID. [ABSTRACT FROM AUTHOR]

Intermolecular C−H silylation for the synthesis of acyclic silanes bearing a silicon‐stereogenic center in one enantiomeric form remains unknown to date. Herein, we report the first enantioselective intermolecular C−H silylation of heteroarenes for the synthesis of acyclic silicon‐stereogenic heteroarylsilanes. This process undergoes a rhodium‐catalyzed direct intermolecular dehydrogenative Si−H/C−H cross‐coupling, giving access to a variety of acyclic heteroarylated silicon‐stereogenic monohydrosilanes, including bis‐Si‐stereogenic silanes, in decent yields with excellent chemo‐, regio‐, and stereo‐control, which significantly enlarge the chemical space of the optically active silicon‐stereogenic monohydrosilanes. [ABSTRACT FROM AUTHOR]

An efficient electrochemical radical silyl‐oxygenation of electron‐deficient alkenes is demonstrated, which gives access to a variety of new highly functionalized silicon‐containing molecules, including β‐silyl‐cyanohydrin derivatives in good yields with excellent chemo‐ and regio‐selectivity. This electrochemical radical silylation process conducts under mild conditions without the use of transition metal catalyst or chemical oxidant and exhibits a wide scope of substrate silanes with high functional‐group tolerance. The ability to access silyl radicals using electrochemical Si−H activation offers new perspectives for the synthesis of valuable organosilicon compounds in a sustainable and green manner. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: An anodic oxidation enabled synthesis of hypervalent iodine(III) reagents from aryl iodides is demonstrated. Under mild electrochemical conditions, a range of aryliodine(III) reagents including iodosylarenes, (difunctionaliodo)arenes, benziodoxoles and diaryliodonium salts can be efficiently synthesized and derivatized in good to excellent yields with high selectivity. As only electrons serve as the oxidation reagents, this method offers a more straightforward and sustainable manner avoiding the use of expensive or hazardous chemical oxidants. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: An anodic oxidation enabled synthesis of hypervalent iodine(III) reagents from aryl iodides is demonstrated. Under mild electrochemical conditions, a range of aryliodine(III) reagents including iodosylarenes, (difunctionaliodo)arenes, benziodoxoles and diaryliodonium salts can be efficiently synthesized and derivatized in good to excellent yields with high selectivity. As only electrons serve as the oxidation reagents, this method offers a more straightforward and sustainable manner avoiding the use of expensive or hazardous chemical oxidants. [ABSTRACT FROM AUTHOR]

Many plants grown with low‐millimolar concentration of NH4+ as a sole nitrogen source develop NH4+‐toxicity symptoms. To date, crucial molecular identities and a practical approach involved in the improvement of plant NH4+‐tolerance remain largely unknown. By phenotyping of upland cotton grown on varied nitrogen forms, we came across a phenomenon that caused sub‐millimolar concentrations of urea (e.g., up 50 μM) to repress the growth inhibition of roots and whole plant cultivated in a NH4+‐containing nutrient solution. A growth‐recovery assay revealed that the relief in NH4+‐inhibited growth required only a short‐term exposure (≧12 h) of the roots to urea, implying that urea could elicit an internal signaling and be involved in antagonizing NH4+‐sensitivity. Intriguingly, split‐root experiments demonstrated that low urea occurrence in one root‐half could efficaciously stimulate not only supplied root but also the root‐half grown in NH4+‐solution without urea, indicating the existence of urea‐triggered local and systemic long‐distance signaling. In the split‐root experiment we also observed high arginase activity, strong arginine reduction and remarkable upregulation of polyamine biosynthesis‐related genes (ADC1/2, SPDS and SPMS). Therefore, we suggest that external urea might serve as an effective cue (signal molecule) in an arginine‐/polyamine‐related process for ameliorating NH4+‐suppressed root growth, providing a novel aspect for deeper exploring and understanding plant NH4+‐tolerance. [ABSTRACT FROM AUTHOR]

Vascular cognitive impairment and dementia (VCID) is defined as a progressive dementia disease related to cerebrovascular injury and often occurs in aged populations. Despite decades of research, effective treatment for VCID is still absent. The pathological processes of VCID are mediated by the molecular mechanisms that are partly modulated at the post‐transcriptional level. As small endogenous non‐coding RNAs, microRNAs (miRs) can regulate target gene expression through post‐transcriptional gene silencing. miRs have been reported to play an important role in the pathology of VCID and have recently been suggested as potential novel pharmacological targets for the development of new diagnosis and treatment strategies in VCID. In this review, we summarize the current understanding of VCID, the possible role of miRs in the regulation of VCID and attempt to envision future therapeutic strategies. Since manipulation of miR levels by either pharmacological or genetic approaches has shown therapeutic effects in experimental VCID models, we also emphasize the potential therapeutic value of miRs in clinical settings. [ABSTRACT FROM AUTHOR]

Microvascular endothelial cell (EC) injury and the subsequent blood‐brain barrier (BBB) breakdown are frequently seen in many neurological disorders, including stroke. We have previously documented that peroxisome proliferator‐activated receptor gamma (PPARγ)‐mediated cerebral protection during ischemic insults needs Krüppel‐like factor 11 (KLF11) as a critical coactivator. However, the role of endothelial KLF11 in cerebrovascular function and stroke outcome is unclear. This study is aimed at investigating the regulatory role of endothelial KLF11 in BBB preservation and neurovascular protection after ischemic stroke. EC‐targeted overexpression of KLF11 significantly mitigated BBB leakage in ischemic brains, evidenced by significantly reduced extravasation of BBB tracers and infiltration of peripheral immune cells, and less brain water content. Endothelial cell‐selective KLF11 transgenic (EC‐KLF11 Tg) mice also exhibited smaller brain infarct and improved neurological function in response to ischemic insults. Furthermore, EC‐targeted transgenic overexpression of KLF11 preserved cerebral tight junction (TJ) levels and attenuated the expression of pro‐inflammatory factors in mice after ischemic stroke. Mechanistically, we demonstrated that KLF11 directly binds to the promoter of major endothelial TJ proteins including occludin and ZO‐1 to promote their activities. Our data indicate that KLF11 functions at the EC level to preserve BBB structural and functional integrity, and therefore, confers brain protection in ischemic stroke. KLF11 may be a novel therapeutic target for the treatment of ischemic stroke and other neurological conditions involving BBB breakdown and neuroinflammation. [ABSTRACT FROM AUTHOR]

Exploitation of efficient and stable photocatalyst for water splitting is pressing to solve the energy crisis. Four CdS@MoS2 nano‐heterojunctions were prepared by a single precursor thermal decomposition combined with one‐step hydrothermal method. The morphology of the prepared samples is spherical and has obvious core‐shell structure interface. The photocurrent of CdS@MoS2‐2 wt% is the largest, which is more over 40 times that of the pure CdS. In addition, CdS@MoS2‐2 wt% had superior photocatalytic H2 generation activity (20.23 mmol g−1 h−1) without any noble metal as a cocatalyst under visible light and show marked photocatalytic durability after a continuous test for 16 hours. This work provides a new insight for the design of core‐shell nano‐heterojunctions for other metal sulfide composites. [ABSTRACT FROM AUTHOR]

Zultanite is the commercial name of a gem‐quality transparent diaspore that exhibits an obvious color change when exposed to different light sources. It usually appears green under daylight and red under incandescent light. This optical feature makes zultanite valuable, and the study of the spectral characteristics, as well as chemical composition, of zultanite can increase our understanding of the associated color change mechanism. Spectral transmittance curves for zultanite exposed to nonpolarized light emitted by CIE standard illuminants D65 and A show that the color change phenomenon is related to the optical characteristics of light sources. The colorimetric parameters in the CIE 1976 L*a*b* uniform color space system illustrate that the color change exhibited by zultanite is an example of the alexandrite effect, which can be quantitatively described by the significant change of a* and h° parameters. These findings and the results of chemical element analysis by X‐ray fluorescence and X‐ray photoelectron spectroscopy imply that electron transitions between different energy levels involving the 3d orbitals of the trace elements Fe3+ and Cr3+ in zultanite give rise to the relatively high transmittance observed in the green region (around 500 nm) and the orange‐red region (600‐780 nm) of visible light. Thus, the difference in the spectral power distributions of different ambient light sources greatly influence the color of zultanite, making zultanite show green under daylight which is richer in the green light and turns red under incandescent light in which the orange‐red light dominates. Summary: The main contributions of this article can be summarized as follows: The colorimetric parameters of zultanite illustrate that its color change phenomenon is an example of the alexandrite effect.The trace elements Fe3+ and Cr3+ are the essential factors that cause the alexandrite effect, which give rise to the relatively high transmittance observed in the green and orange‐red regions of visible light.This article will inspire deeper research on the optical properties and application of hydroxides. [ABSTRACT FROM AUTHOR]

Ammonium (NH4+) represents a primary nitrogen source for many plants, its effective transport into and between tissues and further assimilation in cells determine greatly plant nitrogen use efficiency. However, biological components involved in NH4+ movement in woody plants are unclear. Here, we report kinetic evidence for cotton NH4+ uptake and molecular identification of certain NH4+ transporters (AMTs) from cotton (Gossypium hirustum). A substrate‐influx assay using 15N‐isotope revealed that cotton possessed a high‐affinity transport system with a Km of 58 μM for NH4+. Sequence analysis showed that GhAMT1.1–1.3 encoded respectively a membrane protein containing 485, 509 or 499 amino acids. Heterologous functionality test demonstrated that GhAMT1.1–1.3 expression mediated NH4+ permeation across the plasma membrane (PM) of yeast and/or Arabidopsis qko‐mutant cells, allowing a growth restoration of both mutants on NH4+. Quantitative PCR measurement showed that GhAMT1.3 was expressed in roots and leaves and markedly up‐regulated by N‐starvation, repressed by NH4+ resupply and regulated diurnally and age‐dependently, suggesting that GhAMT1.3 should be a N‐responsive gene. Importantly, GhAMT1.3 expression in Arabidopsis improved plant growth on NH4+ and enhanced total nitrogen accumulation (∼50% more), conforming with the observation of 2‐fold more NH4+ absorption by GhAMT1.3‐transformed qko plant roots during a 1‐h root influx period. Together with its targeting to the PM and saturated transport kinetics with a Km of 72 μM for NH4+, GhAMT1.3 is suggested to be a high‐affinity NH4+ permease that may play a significant role in cotton NH4+ acquisition and utilization, adding a new member in the plant AMT family. [ABSTRACT FROM AUTHOR]

Soil water potential and fertilizer nutrients are the two main factors affecting rice growth and development. A soil-grown experiment was conducted using mid-season japonica rice cultivar Xudao 3 with three different nitrogen (N) fertilization rates: (i) none, (ii) moderate nitrogen (240 kg ha-1), and (iii) high nitrogen (360 kg ha-1) and three irrigation regimes: (i) submerged irrigation (0 kPa), (ii) alternate wetting and moderate drying (-20 kPa), and (iii) alternate wetting and severe drying (-40 kPa). In the same N level, root length, root dry weight, root activity (represented by root-bleeding sap), net photosynthetic rates at main growth stages, and ATPase activity during the grain-filling stage are higher under the treatment of alternate wetting and moderate drying, when compared with those of submerged irrigation. Meanwhile, non-structural carbohydrate (NSC) remobilization and shoot dry accumulation are also increased from heading to maturity, which contribute to higher grain yield and higher nitrogen-use efficiency. In the same irrigation regime, root-bleeding sap, NSC remobilization, and ATPase are increased significantly under the moderate-N treatment compared with those of the high-N treatment, which contribute to higher nitrogen-use efficiency. However, no significant difference exists in grain yield and crop growth rate. These results indicate that the coordinated relationship between the root and shoot, especially increased root length, enhanced root-bleeding sap, increased NSC remobilization, enhanced shoot dry accumulation, and ATPase activity during the grain-filling stage, can promote rice yield and nitrogen- use efficiency by using the appropriate nitrogen application and alternate wetting and moderate drying. [ABSTRACT FROM AUTHOR]

A catalyst‐ and metal‐free electrochemical hydrodehalogenation of aryl halides is disclosed. Our reaction by a flexible protocol is operated in an undivided cell equipped with an inexpensive graphite rod anode and cathode. Trialkylamines nBu3N/Et3N behave as effective reductants and hydrogen atom donors for this electrochemical reductive reaction. Various aryl and heteroaryl bromides worked effectively. The typically less reactive aryl chlorides and fluorides can also be smoothly converted. The utility of our method is demonstrated by detoxification of harmful pesticides and hydrodebromination of a dibrominated biphenyl (analogues of flame‐retardants) in gram scale. [ABSTRACT FROM AUTHOR]

The design of artificial metalloenzymes has achieved tremendous progress, although few designs can achieve catalytic performances comparable to that of native enzymes. Moreover, the structure and function of artificial metalloenzymes in non-native states has rarely been explored. Herein, we found that a c-type cytochrome b5 (Cyt b5), N57C/S71C Cyt b5, with heme covalently attached to the protein matrix through two Cys-heme linkages, adopts a non-native state with an open heme site after guanidine hydrochloride (Gdn ⋅HCl)-induced unfolding, which facilitates H2O2 activation and substrate binding. Stopped-flow kinetic studies further revealed that c-type Cyt b5 in the non-native state exhibited impressive peroxidase activity comparable to that of native peroxidases, such as the most efficient horseradish peroxidase. This study presents an alternative approach to the design of functional artificial metalloenzymes by exploring enzymatic functions in non-native states. [ABSTRACT FROM AUTHOR]

Simple and inexpensive polyhalides (CCl4 and C2Cl6) have been found to be effective and versatile oxidants in removing electrons from Breslow intermediates under N-heterocyclic carbene (NHC) catalysis. This oxidative reaction involves multiple single-electron-transfer (SET) processes and several radical intermediates. The α, β, and γ-carbon atoms of aldehydes and enals could be readily functionalized. Given the low cost of the oxidants and the broad applicability of the reactions, this study is expected to greatly enhance the feasibility of oxidative NHC catalysis for large-scale applications. Also this new SET radical process with polyhalides as single-electron oxidants will open a new avenue in the development of NHC-catalyzed radical reactions. [ABSTRACT FROM AUTHOR]

Rational protein design has been proven to be a powerful tool for creating functional artificial proteins. Although many artificial metalloproteins with a single active site have been successfully created, those with dual active sites in a single protein scaffold are still relatively rare. In this study, we rationally designed dual active sites in a single heme protein scaffold, myoglobin (Mb), by retaining the native heme site and creating a copper-binding site remotely through a single mutation of Arg118 to His or Met. Isothermal titration calorimetry (ITC) and electron paramagnetic resonance (EPR) studies confirmed that a copper-binding site of [3-His] or [2-His-1-Met] motif was successfully created in the single mutant of R118H Mb and R118M Mb, respectively. UV/Vis kinetic spectroscopy and EPR studies further revealed that both the heme site and the designed copper site exhibited nitrite reductase activity. This study presents a new example for rational protein design with multiple active sites in a single protein scaffold, which also lays the groundwork for further investigation of the structure and function relationship of heme/non-heme proteins. [ABSTRACT FROM AUTHOR]

For the first time, a versatile electrolyte bath is described that can be used to electrodeposit a wide range of p-block elements from supercritical difluoromethane (scCH2F2). The bath comprises the tetrabutylammonium chlorometallate complex of the element in an electrolyte of 50×10–3 moldm–3 tetrabutylammonium chloride at 17.2 MPa and 358 K. Through the use of anionic ([GaCl4]–, [InCl4]–, [GeCl3]–, [SnCl3]–, [SbCl4]–, and [BiCl4]–) and dianionic ([SeCl6]2– and [TeCl6]2–) chlorometallate salts, the deposition of elemental Ga, In, Ge, Sn, Sb, Bi, Se, and Te is demonstrated. In all cases, with the exception of gallium, which is a liquid under the deposition conditions, the resulting deposits are characterised by SEM, energy-dispersive X-ray analysis, XRD and Raman spectroscopy. An advantage of this electrolyte system is that the reagents are all crystalline solids, reasonably easy to handle and not highly water or oxygen sensitive. The results presented herein significantly broaden the range of materials accessible by electrodeposition from supercritical fluid and open up the future possibility of utilising the full scope of these unique fluids to electrodeposit functional binary or ternary alloys and compounds of these elements. [ABSTRACT FROM AUTHOR]

The selective radical/radical cross-coupling of two different organic radicals is a great challenge due to the inherent activity of radicals. In this paper, a copper-catalyzed radical/radical C [ABSTRACT FROM AUTHOR]

Asymmetric Catalysis, Dehydrogenative Coupling, Rhodium, Silylation, Stereogenic Silanes Keywords: Asymmetric Catalysis; Dehydrogenative Coupling; Rhodium; Silylation; Stereogenic Silanes EN Asymmetric Catalysis Dehydrogenative Coupling Rhodium Silylation Stereogenic Silanes 1 1 1 05/11/22 20220516 NES 220516 B Asymmetrische Katalyse b In ihrer Zuschrift (e202117820) berichten Chuan He et al. über die enantioselektive intermolekulare C-H-Silylierung von Heteroarenen zur Synthese von azyklischen Si-stereogenen Silanen. Frontispiz: Enantioselective Intermolecular C-H Silylation of Heteroarenes for the Synthesis of Acyclic Si-Stereogenic Silanes. [Extracted from the article]

The impurity transition element chromium Cr3+ in ruby can be excited to high energy levels by absorbing visible light. When the excited Cr3+ returns to ground state through an intermediate energy level, the ruby emits red light as fluorescence. The fluorescence of ruby is actually caused by visible light, not by ultraviolet. The color of ruby is attributed to both the absorption and the fluorescence. The spectrum of a natural ruby under visible light is directly measured by a dual integrating sphere spectrometer. The measured spectrum includes both the spectral reflectance and the fluorescence caused by visible light. This study confirmed that the red fluorescence of ruby is indeed caused by visible light, not by ultraviolet radiation. In addition, average color of the ruby is calculated from the measured spectrum, and true color grade is also obtained by the artificial intelligent software of the spectrometer. © 2012 Wiley Periodicals, Inc. Col Res Appl, 38, 328-333, 2013 [ABSTRACT FROM AUTHOR]

Geschwindigkeitsbestimmend: Für die Sonogashira ‐ Kupplung wird gezeigt, dass die Transmetallierung der geschwindigkeitsbestimmende Schritt ist. Die Kreuzkupplung ist ein Pd ‐ und Cu ‐ katalysierter synergistischer Prozess, der bezüglich der [Pd] ‐ und [Cu] ‐ Katalysatoren nach einer Kinetik erster Ordnung verläuft. [ABSTRACT FROM AUTHOR]

The article discusses a study on the mechanical properties and particle distribution of nano-calcium carbonate (CaCO3)/ethylene-propylene-diene terpolymer (EPDM)/polypropylene (PP) with high content of nano-CaCO3. It examines the impact strength, interfacial tension, and phase morphology of the ternary composite. Moreover, the scanning electron microscope images show existence of nano fibrils at the interface between nano-CaCO3 agglomerates and matrix.

A three-stage 7- to 14-GHz monolithic low-noise amplifier (LNA) has been fabricated using 0.15-μm AlGaAs/GaAs pHEMT technology.To achieve ultra low noise figure and wide operation bandwidth, the proposed LNA uses wideband matching network and negative feedback technique. Measured results from 7 to 14 GHz demonstrate a minimum of 1.1 dB noise figure and 26 dB gain. The input and output return loss exceeded 10 dB across the band. These results demonstrate the best performance of AlGaAs/GaAs pHEMT technology for wideband and low noise applications. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2615–2617, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25547 [ABSTRACT FROM AUTHOR]

Silacycles have exhibited significant potential for application in the fields of medicinal chemistry, agrochemistry, and materials science. Accordingly, the development of effective methods for synthesizing these compounds has attracted increasing attention. Here, we report an efficient Cu‐catalyzed enantioselective hydrosilylation of arylmethylenecyclopropanes with hydrosilanes, that allows the rapid assembly of various enantioenriched carbon‐ and silicon‐stereogenic silacyclopentanes in good yields with excellent enantioselectivities and diastereoselectivities under mild conditions. Further stereospecific transformation of the Si−H bond on the chiral silicon center expands the diversity of these C‐ and Si‐stereogenic silacyclopentanes. [ABSTRACT FROM AUTHOR]

A diagram is presented which shows the chemical formulas for organo-phosphorus compounds, copper and phosphorylation of aryl ketone o-acetyloximes.

A novel method is reported for the synthesis of pyrroles (III) by a silver-mediated oxidative cross-coupling/cyclization of β-enamino esters (I) with aryl alkynes (II). [ABSTRACT FROM AUTHOR]

leading to β-aryl esters and amides [ABSTRACT FROM AUTHOR]

In the crystal of the title compound, C(16)H(17)N(2) (+)·NO(3) (-)·H(2)O, the tetra-methyl-1,10-phenanthrolinium cations, nitrate anions and lattice water mol-ecules are all located on a mirror plane with the methyl H atoms of the cation equally disordered over two sites about the mirror plane. The cation, anion and water mol-ecule are linked by O-H⋯O and N-H⋯O hydrogen bonds into a sheet parallel to the bc plane. π-π stacking between phenanthroline ring systems is observed in the crystal structure, the centroid-centroid distance being 3.4745 (6) Å.