Durhamstevens9535

Herein, we disclose a nickel-catalyzed three-component reaction of internal enamide, diethoxymethylsilane, and aryl iodide to provide expedient access to benzylic amide derivatives. The protocol features a broad substrate scope with a moderate to excellent isolated yield under the mild condition. The high regioselectivity of Ni-catalyzed enamide hydroarylation can be attributed to the directing effect by the prefunctionalized nitrogen-containing group on the alkenes.A new family of α, α directly linked bisBODIPYs was developed through a MoCl5-mediated intramolecular oxidative reaction. Due to the coplanar structure of the two conformationally locked BODIPY units, these bisBODIPYs showed well-extended conjugations and gave strong near-infrared absorptions and emissions with maxima around 760 and 780 nm, respectively, with high fluorescence quantum yields of ≤0.84. These dyes were successfully applied for in vitro and in vivo fluorescence imaging by taking advantage of their beneficial photophysical properties.Palladium-catalyzed intramolecular tandem cyclization reactions were conducted for the synthesis of densely cis/cis-fused aza-tetracyclic structures. The process involved a palladium(II)-catalyzed aerobic aza-Wacker reaction, followed by a palladium(0)-catalyzed Heck reaction. The effects of the solvent and benzene substitution pattern on the one-pot, two-step cascade reaction were studied systematically, and a probable mechanism was proposed. Strained pentahydrobenzo[f]cyclopenta[hi]indolizin-6-one and racemic γ-lycorane can also be synthesized rapidly using this palladium-catalyzed aza-Wacker-Heck cyclization reaction.Since it was recently demonstrated in a spin-valve structure, magnetization reversal of a ferromagnetic layer using a single ultrashort optical pulse has attracted attention for future ultrafast and energy-efficient magnetic storage or memory devices. However, the mechanism and the role of the magnetic properties of the ferromagnet as well as the time scale of the magnetization switching are not understood. Here, we investigate single-shot all-optical magnetization switching in a GdFeCo/Cu/[Co x Ni1-x/Pt] spin-valve structure. We demonstrate that the threshold fluence for switching both the GdFeCo and the ferromagnetic layer depends on the laser pulse duration and the thickness and the Curie temperature of the ferromagnetic layer. We are able to explain most of the experimental results using a phenomenological model. This work provides a way to engineer ferromagnetic materials for energy efficient single-shot all-optical magnetization switching.The Hall scattering factor, r, is a key quantity for establishing carrier concentration and drift mobility from Hall measurements; in experiments, it is usually assumed to be 1. In this paper, we use a combination of analytical and ab initio modeling to determine r in graphene. Although at high carrier densities r ≈ 1 in a wide temperature range, at low doping the temperature dependence of r is very strong with values as high as 4 below 300 K. These high values are due to the linear bands around the Dirac cone and the carrier scattering rates due to acoustic phonons. At higher temperatures, r can instead become as low as 0.5 due to the contribution of both holes and electrons and the role of optical phonons. Finally, we provide a simple analytical model to compute accurately r in graphene in a wide range of temperatures and carrier densities.We describe herein an efficient and selective Ru-catalyzed intramolecular HDF directed by a silyl group, which is readily installed, and removable and transformable following the HDF reaction. The hydrosilyl group in polyfluoroaryl silane acts not only as the directing group but also as the internal reductant, enabling precise control of the ortho-selectivity and avoiding overdefluorination. Mechanistic studies reveal a plausible catalytic cycle involving a Ru(IV)-aryne intermediate.SiO2 is bioinert and highly functionalizable, thus making it a very attractive material for nanotechnology applications such as drug delivery and nanoencapsulation of pesticides. Herein, we synthesized porous hollow SiO2 nanoparticles (PHSNs) by using cetyltrimethylammonium bromide (CTAB) and Pluronic P123 as the structure-directing agents. The porosity and hollowness of the SiO2 structure allow for the protective and high-density loading of molecules of interest inside the nanoshell. We demonstrate here that loading can be achieved post-synthesis through the pores of the PHSNs. The PHSNs are monodisperse with a mean diameter of 258 nm and a specific surface area of 287 m2 g-1. The mechanism of formation of the PHSNs was investigated using 1-D and 2-D solid-state nuclear magnetic resonance (SS-NMR) and Fourier-transform infrared spectroscopy (FTIR). The data suggest that CTAB and Pluronic P123 interact, forming a hydrophobic spherical hollow cage that serves as a template for the porous hollow structure. After synthesis, the surfactants were removed by calcination at 550 °C and the PHSNs were added to an Fe3+ solution followed by addition of the reductant NaBH4 to the suspension, which led to the formation of Fe(0) NPs both on the PHSNs and inside the hollow shell, as confirmed by transmission electron microscopy imaging. The imaging of the formation of Fe(0) NPs inside the hollow shell provides direct evidence of transport of solute molecules across the shell and their reactions within the PHSNs, making it a versatile nanocarrier and nanoreactor.A concise, organocatalytic, enantioselective route to the γ-lactam core of the oxazolomycins was developed. Key steps include a Lewis base-catalyzed, Michael proton transfer-lactamization organocascade, a one-pot N-methylation and diastereoselective α-alkylation, a diastereotopic group-selective reduction, a substrate-directed allylic hydroxylation, and a lanthanide-mediated organolithium addition to append the side chain. A formal synthesis of (+)-neooxazolomycin via interception of a Kende intermediate, accessed in 10 steps (previously 24 steps from α-d-glucose), enabled confirmation of the relative and absolute stereochemistry.Electrostatically defined quantum dots (QDs) in Bernal stacked bilayer graphene (BLG) are a promising quantum information platform because of their long spin decoherence times, high sample quality, and tunability. Importantly, the shape of QD states determines the electron energy spectrum, the interactions between electrons, and the coupling of electrons to their environment, all of which are relevant for quantum information processing. Despite its importance, the shape of BLG QD states remains experimentally unexamined. Here we report direct visualization of BLG QD states by using a scanning tunneling microscope. Strikingly, we find these states exhibit a robust broken rotational symmetry. By using a numerical tight-binding model, we determine that the observed broken rotational symmetry can be attributed to low energy anisotropic bands. We then compare confined holes and electrons and demonstrate the influence of BLG's nontrivial band topology. Our study distinguishes BLG QDs from prior QD platforms with trivial band topology.Phosphopeptide enrichment is an essential step in large-scale, quantitative phosphoproteomics by mass spectrometry. Several phosphopeptide affinity enrichment techniques exist, such as immobilized metal-ion affinity chromatography (IMAC) and metal oxide affinity chromatography (MOAC). We compared zirconium(IV) IMAC (Zr-IMAC) magnetic microparticles to more commonly used titanium(IV) IMAC (Ti-IMAC) and TiO2 magnetic microparticles for phosphopeptide enrichment from simple and complex protein samples prior to phosphopeptide sequencing and characterization by mass spectrometry (liquid chromatography-tandem mass spectrometry, LC-MS/MS). We optimized sample-loading conditions to increase phosphopeptide recovery for Zr-IMAC-, Ti-IMAC-, and TiO2-based workflows by 22, 24, and 35%, respectively. 2,6-Dihydroxypurine The optimized protocol resulted in improved performance of Zr-IMAC over Ti-IMAC and TiO2 as well as high-performance liquid chromatography-based Fe(III)-IMAC with up to 23% more identified phosphopeptides. The different enrichment chemistries showed a high degree of overlap but also differences in phosphopeptide selectivity and complementarity. We conclude that Zr-IMAC improves phosphoproteome coverage and recommend that this complementary and scalable affinity enrichment method is more widely used in biological and biomedical studies of cell signaling and the search for biomarkers. Data are available via ProteomeXchange with identifier PXD018273.Integration of ionic permselective medium (e.g., nanochannels, membranes) within microfluidic channels has been shown to enable on-chip desalination, sample purification, bioparticle sorting, and biomolecule concentration for enhanced detection sensitivity. However, the ion-permselective mediums are generally of fixed properties and cannot be dynamically tuned. Here we study a microfluidic device consisting of an array of individually addressable elastic membranes connected in series on top of a single microfluidic channel that can be deformed to locally reduce the channel cross-section into a nanochannel. Dynamic tunability of the ion-permselective medium, as well as controllability of its location and ionic permselectivity, introduces a new functionality to microfluidics-based lab-on-a-chip devices, for example, dynamic localization of preconcentrated biomolecule plugs at different sensing regions for multiplex detection. Moreover, the ability to simultaneously form a series of preconcentrated plugs at desired locations increases parallelization of the system and the trapping efficiency of target analytes.A redox-responsive oil-in-dispersion emulsion was developed by using a cationic ferrocene surfactant (FcCOC10N) and Al2O3 nanoparticles, in which the required concentrations of FcCOC10N and Al2O3 nanoparticles are as low as 0.001 mM (≈0.005 cmc) and 0.006 wt %, respectively. Rapid demulsification can be successfully achieved through a redox trigger, resulting from the transition of FcCOC10N from a normal cationic surfactant form into a strongly hydrophilic Bola type form (Fc+COC10N). Moreover, Fc+COC10N together with the particles almost resides in the aqueous phase and can be recovered after the reduction reaction. Not only the amount of surfactant and nanoparticles are significantly reduced but also the emulsifier (surfactant and alumina) can be recycled and reused from the aqueous phase, which is a sustainable and economical strategy for various applications.In this research, through the use of molecular dynamics (MD) simulations, the ability of gold nanoparticles (AuNPs) functionalized by different groups, such as 3-mercaptoethylsulfonate (Mes), undecanesulfonic acid (Mus), octanethiol (Ot), and a new peptide, to inhibit severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was investigated. According to the crystal structure of angiotensin-converting enzyme 2 (ACE2), which binds to the SARS-CoV-2 receptor binding domain (RBD), 15 amino acids of ACE2 have considerable interaction with RBD. Therefore, a new peptide based on these amino acids was designed as the functional group for AuNP. On the basis of the obtained results, functionalized AuNPs have remarkable effects on the RBD and strongly interact with this protein of SARS-CoV-2. Among the studied nanoparticles, the AuNP functionalized by new peptide forms a more stable complex with RBD in comparison with ACE2, which is the human receptor for SARS-CoV-2. Different analyses confirm that the designed AuNPs can be good candidates for antiviral agents against COVID-19 disease.