We report acute antibody responses to SARS-CoV-2 in 285 patients with COVID-19. Within 19 days after symptom onset, 100% of patients tested positive for antiviral immunoglobulin-G (IgG). ...Seroconversion for IgG and IgM occurred simultaneously or sequentially. Both IgG and IgM titers plateaued within 6 days after seroconversion. Serological testing may be helpful for the diagnosis of suspected patients with negative RT-PCR results and for the identification of asymptomatic infections.
Understanding the mechanisms of chemical reactions, especially catalysis, has been an important and active area of computational organic chemistry, and close collaborations between experimentalists ...and theorists represent a growing trend. This Perspective provides examples of such productive collaborations. The understanding of various reaction mechanisms and the insight gained from these studies are emphasized. The applications of various experimental techniques in elucidation of reaction details as well as the development of various computational techniques to meet the demand of emerging synthetic methods, e.g., C–H activation, organocatalysis, and single electron transfer, are presented along with some conventional developments of mechanistic aspects. Examples of applications are selected to demonstrate the advantages and limitations of these techniques. Some challenges in the mechanistic studies and predictions of reactions are also analyzed.
Photoinduced Pd‐catalyzed bisfunctionalization of butadienes with a readily available organic halide and a nucleophile represents an emerging and attractive method to assemble versatile alkenes ...bearing various functional groups at the allylic position. However, enantiocontrol and/or diastereocontrol in the C−C or C−X bond‐formation step have not been solved due to the open‐shell process. Herein, we present a cascade asymmetric dearomatization reaction of indoles via photoexcited Pd‐catalyzed 1,2‐biscarbonfunctionalization of 1,3‐butadienes, wherein asymmetric control on both the nucleophile and electrophile part is achieved for the first time in photoinduced bisfunctionalization of butadienes. This method delivers structurally novel chiral spiroindolenines bearing two contiguous stereogenic centers with high diastereomeric ratios (up to >20 : 1 dr) and good to excellent enantiomeric ratios (up to 97 : 3 er). Experimental and computational studies of the mechanism have confirmed a radical pathway involving excited‐state palladium catalysis. The alignment and non‐covalent interactions between the substrate and the catalyst were found to be essential for stereocontrol.
Herein, a cascade asymmetric dearomatization reaction of indoles via photoinduced Pd‐catalyzed 1,2‐biscarbonfunctionalization of 1,3‐butadienes has been disclosed. This process delivers structurally novel chiral spiroindolenines bearing two contiguous stereogenic centers with high diastereomeric ratios (up to >20 : 1 dr) and good to excellent enantiomeric ratios (up to 97 : 3 er).
A combined ion‐mobility mass spectrometry (IM‐MS) and DFT study has been employed to investigate the mechanism and the origin of selectivity of palladium/mono‐N‐protected amino acid (MPAA)‐catalyzed ...enantioselective CH activation reactions of several prochiral substrates. We captured the Pd(MPAA)(substrate) complex at different stages, and demonstrated that the CH bond can be activated in the absence of an external base. DFT studies lead to the establishment of a significantly modified relay mechanism invoking a key conformational effect to account for the origin of enantioselectivity. This relay mechanism successfully accounts for the enantioselectivity for all the relevant reactions reported. The enantioselectivity originates from the rigid square‐planar Pd coordination in the CH activation transition state: Bidentate MPAA and substrate coordination.
Relay of chirality: A combined ion‐mobility mass spectrometry (IM‐MS) and DFT study has been carried out to investigate chiral Pd/monoprotected amino acid (MPAA)‐enabled direct asymmetric CH activation reactions. The enantioselectivity originates from the rigid square‐planar Pd coordination in the CH activation transition state: Bidentate MPAA and substrate coordination (see figure: DG=directing group).
Tungsten has been considered as one of suitable candidate as plasma-facing material for the first wall of fusion devices. However, the application of tungsten in fusion reactions presents risk ...because of the brittleness, high ductile–brittle transition temperature, and other defects of tungsten materials. Studies have shown that ultrafine-grained/nanostructured tungsten materials can improve these problems. In its first part this article describes the powder metallurgy techniques for the preparation of ultrafine-grained/nanostructured tungsten. And the second part of this article reviews bulk processes for the preparation. The possibility of preparing ultrafine-grained/nanostructured tungsten and referenceable process parameters are described. By describing the mechanical properties and irradiation performance of ultrafine-grained/nanostructured tungsten, the research prospects and development directions of tungsten materials for fusion reactors are indicated.
•Formation mechanism of the ultrafine-grained/nanostructured arrangements and their effects on the properties are reviewed.•Adding Ti played a positive role in improving the oxidation resistance of the alloy.•WCrY alloy has more excellent oxidation resistance than WCrTi ternary alloy.•WCrY alloy after annealing has better oxidation resistance.
Abstract
Background
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a novel β-coronavirus, causes severe pneumonia and has spread throughout the globe rapidly. The disease associated ...with SARS-CoV-2 infection is named coronavirus disease 2019 (COVID-19). To date, real-time reverse-transcription polymerase chain reaction (RT-PCR) is the only test able to confirm this infection. However, the accuracy of RT-PCR depends on several factors; variations in these factors might significantly lower the sensitivity of detection.
Methods
In this study, we developed a peptide-based luminescent immunoassay that detected immunoglobulin (Ig)G and IgM. The assay cutoff value was determined by evaluating the sera from healthy and infected patients for pathogens other than SARS-CoV-2.
Results
To evaluate assay performance, we detected IgG and IgM in the sera from confirmed patients. The positive rate of IgG and IgM was 71.4% and 57.2%, respectively.
Conclusions
Therefore, combining our immunoassay with real-time RT-PCR might enhance the diagnostic accuracy of COVID-19.
A peptide-based magnetic chemiluminescence enzyme immunoassay for the detection of SARS-CoV-2 antibodies was developed; 71.4% (197 of 276) and 57.2% (158 of 276) of the COVID-19 inpatients were positive for IgG and IgM against SARS-CoV-2.
A combined experimental/computational study on the amino acid ligand-assisted Pd-catalyzed C–H bond activation reveals a mechanism in which the amino acid acts as both a dianionic bidentate ligand ...and a proton acceptor. This new model explains the effects of amino acids on reactivity and selectivity and unveils the dual roles of amino acids: stabilizing monomeric Pd complexes and serving as the internal base for proton abstraction.
To study the role of the Rho/ROCK pathway in Ang II and TGF-β1-induced atrial remodeling.
A canine atrial fibrillation (AF) model was established by rapid atrial pacing (RAP) of the left atrium. The ...roles of TGF-β1, the RhoA/ROCK signaling pathway and connective tissue growth factor (CTGF) in atrial remodeling were studied via both in vitro and in vivo experiments. Each of the dogs that received RAP developed persistent AF within 4 weeks. The mRNA expression levels of TGF-β1 (1.32±0.38), Collagen-I(1.33±0.91), CTGF(5.83±3.71), RhoA(1.23±0.57) and ROCK-1 (1.02±0.27) in the left atrium were significantly increased following 4 weeks of RAP. Angiotensin II (Ang II) induced the proliferation of atrial fibroblasts and up-regulated the expression of both CTGF and ROCK-1 in a dose-dependent manner. Simvastatin and Y27632 reversed Ang II-induced CFs proliferation, as well as ROCK-1(0.89±0.05 and 1.27±0.03, respectively) and CTGF (0.87±0.04 and 0.91±0.02, respectively) expression. The expression mRNA of ROCK-1(1.74±0.13) and CTGF (2.28±0.11) can upregulated by TGF-β1, and down-regulated by Simvastatin (1.22±0.03 vs 2.27±0.11), Y27632 (1.01±0.04 vs 1.64±0.03), Los (1.04±0.11 vs 1.26±0.05), respectively. Losartan and Simvastatin attenuated the effects of TGF-β1, inhibited RhoA activity as opposed to RhoA protein expression. Y27632 had no effect on either the expression or the activity of RhoA.
The increased expression of profibrotic factors (CTGF, ROCK1 and Smad2/3) played an important role in our RAP-induced AF model. Increased atrial profibrotic factors involve the activation of either the TGF-β1/RhoA/ROCK-1 or the TGF-β1/Smad2/3 signaling pathway.
Nonnegligible emission of bioaerosols usually occurs during aeration of wastewater in aerator tanks in wastewater treatment plants (WWTPs). Literature had shown that the respiratory and intestinal ...diseases of workers at WWTPs are related to bioaerosols. Thus, quantitative microbial risk assessment (QMRA) based on Monte Carlo simulation was utilized in this research to assess the health risks of Gram-negative bacteria bioaerosol (GNBB) and
Staphylococcus aureus
bioaerosol (SAB) among academic visitors and staffs. Results showed that the concentrations of GNBB and SAB in the inverted umbrella aeration mode were consistently higher than those in the microporous aeration mode under all six size distribution ranges of the Anderson six-stage impactor. Thus, GNBB and SAB can be highly threatening to the weasand and first bronchus (or alveoli and third bronchus) for the exposure populations. The health risks (annual probability of infection (
P
y
) and disease burden (DB)) of males were constantly higher than those of females for each certain exposure scenario. The health risks of staffs were higher than those of academic visitors when assessed by Monte Carlo simulation. The wearing of mask is an effective measure to minimize health risks through reducing the bioaerosol concentration intake. Especially, for the academic visitors and staffs exposed to GNBB, all their DB failed to meet the World Health Organization DB benchmark under various credible intervals when they were without a mask on. In a word, the results of health risk assessment in this research can be utilized as an educational tool and policy basis to facilitate the implementation of efficacious prevention measures to protect the public health from bioaerosol health threats in WWTPs.
Density functional theory investigations have elucidated the mechanism and origins of meta-regioselectivity of Pd(II)-catalyzed C–H olefinations of toluene derivatives that employ a ...nitrile-containing template. The reaction proceeds through four major steps: C–H activation, alkene insertion, β-hydride elimination, and reductive elimination. The C–H activation step, which proceeds via a concerted metalation–deprotonation (CMD) pathway, is found to be the rate- and regioselectivity-determining step. For the crucial C–H activation, four possible active catalytic speciesmonomeric Pd(OAc)2, dimeric Pd2(OAc)4, heterodimeric PdAg(OAc)3, and trimeric Pd3(OAc)6have been investigated. The computations indicated that the C–H activation with the nitrile-containing template occurs via a Pd–Ag heterodimeric transition state. The nitrile directing group coordinates with Ag while the Pd is placed adjacent to the meta-C–H bond in the transition state, leading to the observed high meta-selectivity. The Pd2(OAc)4 dimeric mechanism also leads to the meta-C–H activation product but with higher activation energies than the Pd–Ag heterodimeric mechanism. The Pd monomeric and trimeric mechanisms require much higher activation free energies and are predicted to give ortho products. Structural and distortion energy analysis of the transition states revealed significant effects of distortions of the template on mechanism and regioselectivity, which provided hints for further developments of new templates.
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