Honeycuttpatrick9233

Palladium-catalyzed Suzuki-Miyaura cross-coupling reactions of liquid, unbiased dibromoarenes under mechanochemical conditions selectively afford the monoarylated products. The lower reactivity of the crystalline monoarylated products relative to the liquid starting materials should be attributed predominantly to the low diffusion efficiency of the former in the reaction mixture, which results in a selective monoarylation. The present study sheds light on a novel approach using in situ phase transitions in solids to design selective organic transformations that are difficult to achieve via conventional solution-based synthesis.In this Article, ZnO nanofibers were prepared by electrospinning. The as-prepared ZnO electrospun fibers were treated with plasma. The morphology, structure, and element content of the ZnO nanofibers greatly changed after treatment with different plasmas. The test results indicated that the acetone-sensing performance was remarkably improved for oxygen-plasma-assisted ZnO nanofibers. Furthermore, the density function theory (DFT) calculation results revealed that the acetone adsorption energy of ZnO nanofibers treated with oxygen plasma was 2 times greater than that of untreated ZnO nanofibers, and the electrons transferred between ZnO nanofibers and acetone molecules produced a more remarkable change in electronic structure for the oxygen-plasma-treated ZnO nanofibers. Our work demonstrates that the oxygen plasma treatment method can help improve the acetone-sensing performance of ZnO nanofibers.In this study, zinc-gallium oxynitrides with a ZnGa mole ratio of 11 [(GaN)0.5(ZnO)0.5] were synthesized from a Zn/Ga/CO3 layered double hydroxide (LDH) precursor. The microstructure and photoactivity of the (GaN)0.5(ZnO)0.5 particles were tuned by adjusting the nitridation conditions of the LDH. It is revealed that the quantity of the LDH, or, equivalently, the partial pressure of the water during nitridation, plays a pivotal role in the defect structure of the obtained oxynitrides. A reduction in the quantity of the LDH precursor can effectively suppress the formation of defects including Ga(Zn)-O bonding, bulk anion vacancies, and surface-deposited Ga/ON···VGa complexes, leading to a better charge-separation efficiency for the photogenerated electron-hole pairs in the oxynitride. Furthermore, a suitable introduction of methane during nitridation would not only increase the crystallinity of the bulk materials but also enhance the density of the surface oxygen vacancy (VO), which would raise the charge-injection efficiency by working as an electron trap and a reaction site to form O2•-. O2•-, as well as photogenerated holes, have been proven to be the dominant active species for the photodegradation of phenol. 25CH4-ZnGaNO, with the lowest density of bulk defects and the highest density of surface VO, exhibited the best photoactivity under visible-light irradiation for the photodegradation of Rhodamine B and phenol. The obtained surface-VO-rich (GaN)0.5(ZnO)0.5 particles can be applied as a high-performance visible-light-driven photocatalyst in the photodegradation of organic pollutants.Volatile methyl siloxanes (VMS) are ubiquitous anthropogenic pollutants that have recently come under scrutiny for their potential toxicity and environmental persistence. In this work, we determined the rate constants for oxidation by OH radicals and Cl atoms at 297 ± 3 K and atmospheric pressure in Boulder, CO (∼860 mbar) of hexamethyldisiloxane (L2), octamethyltrisiloxane (L3), decamethyltetrasiloxane (L4), dodecamethylpentasiloxane (L5), hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5). Measured rate constants with OH radicals were (1.20 ± 0.09) × 10-12, (1.7 ± 0.1) × 10-12, (2.5 ± 0.2) × 10-12, (3.4 ± 0.5) × 10-12, (0.86 ± 0.09) × 10-12, (1.3 ± 0.1) × 10-12, and (2.1 ± 0.1) × 10-12 cm3 molec-1 s-1, for L2, L3, L4, L5, D3, D4, and D5, respectively. The rate constants for reactions with Cl atoms with the same compounds were (1.44 ± 0.05) × 10-10, (1.85 ± 0.05) × 10-10, (2.2 ± 0.1) × 10-10, (2.9 ± 0.1) × 10-10, (0.56 ± 0.05) × 10-10, (1.16 ± 0.08) × 10-10, and (1.8 ± 0.1) × 10-10 cm3 molec-1 s-1, respectively. Substituent factors of F(-Si(CH3)2OR) and F(-SiCH3(OR)2) are proposed for use in AOPWIN, a common model for OH radical rate constant estimations. Cl atoms can remove percentage levels of VMS globally with potentially increased importance in urban areas.An NHC-catalyzed radical relay enabled the vicinal alkylacylation of alkenes using aldehydes and tertiary α-bromo esters as a versatile route to δ-keto esters bearing an all-carbon quaternary center at the position α to the ester. The protocol was applicable to the reaction of tertiary α-bromoamides to afford δ-keto amides. This protocol enabled the conversion of readily available starting materials to congested and functionalized δ-ketocarbonyls in a single step without using transition metals.Per-O-acetylated unnatural monosaccharides containing a bioorthogonal group have been widely used for metabolic glycan labeling (MGL) in live cells for two decades, but it is only recently that we discovered the existence of an artificial "S-glycosylation" between protein cysteines and per-O-acetylated sugars. While efforts are being made to avoid this nonspecific reaction in MGL, the reaction mechanism remains unknown. Here, we present a detailed mechanistic investigation, which unveils the "S-glycosylation" being an atypical glycosylation termed S-glyco-modification. In alkaline protein microenvironments, per-O-acetylated monosaccharides undergo base-promoted β-elimination to form thiol-reactive α,β-unsaturated aldehydes, which then react with cysteine residues via Michael addition. This S-glyco-modification produces 3-thiolated sugars in hemiacetal form, rather than typical glycosides. Carfilzomib chemical structure The elimination-addition mechanism guides us to develop 1,6-di-O-propionyl-N-azidoacetylgalactosamine (1,6-Pr2GalNAz) as an improved unnatural monosaccharide for MGL.The ability of proteins to interconvert unrelated biochemical inputs and outputs underlays most of energy and information processing in biology. A common conversion mechanism involves a conformational change of a protein receptor in response to a ligand binding or a covalent modification, leading to allosteric activity modulation of the effector domain. Designing such systems rationally is a central goal of synthetic biology and protein engineering. Two component sensory systems based on scaffolding of modules in the presence of an analyte is one of the most generalizable biosensor architectures. An inherent problem of such systems is dependence of the response on the absolute and relative concentrations of the components. Here we use the example of two component sensory systems based on calmodulin-operated synthetic switches to analyse and address this issue. We constructed "caged" versions of the activating domain thereby creating a thermodynamic barrier for spontaneous activation of the system. We demonstrate that the caged biosensor architectures could operate at concentrations spanning three orders of magnitude and are applicable to electrochemical, luminescent and fluorescent two component biosensors.