Activity

Accuracy and precision of the method were critically evaluated using a synthetic ALI-containing glutathione adduct. The validated method was subsequently used to detect dose-dependent formation of ALI-protein adducts in human serum albumin exposed to AAI and in proteins isolated from the tissues and sera of AAI-exposed rats. Our time-dependent study showed that ALI-protein adducts remained detectable in rats even at 28 days postdosing. It is anticipated that the developed method will fill the technical gap in diagnosing AA intoxication and facilitate the biomonitoring of human exposures to AAs.Leucosceptroids are sesterterpenoids with potent antifeedant and antifungal activities. In this paper, efforts on two synthetic strategies toward stereoselective total synthesis of the leucosceptroid family of natural products are reported. Intramolecular addition cyclization strategy could lead to a stereochemically mismatched core structure, while intermolecular addition/ring-closing metathesis cyclization strategy successfully furnished an advanced common intermediate bearing eight contiguous stereogenic centers, including three tetra-substituted ones, which fully matches all the stereochemistry on the tricyclic framework in leucosceptroid H. Late-stage transformation of this intermediate to leucosceptroid H encountered difficulty in oxidizing the secondary hydroxyl group to a carbonyl group in the target. Instead of the desired oxidation, an interesting tricyclic spiral product originating from a C-C bond cleavage was observed.Recent experimental studies engaging isotopically substituted protein (heavy protein) have revealed that many, but not all, enzymatic systems exhibit altered chemical steps in response to an altered mass. The results have been interpreted as femtosecond protein dynamics at the active site being linked (or not) to transition-state barrier crossing. An altered enzyme mass can influence several kinetic parameters (kcat, Km, and kchem) in amounts of ≤30% relative to light enzymes. An early report on deuterium-labeled Escherichia coli alkaline phosphatase (AP) showed an unusually large enzyme kinetic isotope effect on kcat. Ilomastat We examined steady-state and chemical step properties of native AP, [2H]AP, and [2H,13C,15N]AP to characterize the role of heavy enzyme protein dynamics in reactions catalyzed by AP. Both [2H]- and [2H,13C,15N]APs showed unaltered steady-state and single-turnover rate constants. These findings characterize AP as one of the enzymes in which mass-dependent catalytic site dynamics is dominated by reactant-linked atomic motions. Two catalytic site zinc ions activate the oxygen nucleophiles in the catalytic site of AP. The mass of the zinc ions is unchanged in light and heavy APs. They are essentially linked to catalysis and provide a possible explanation for the loss of linkage between catalysis and protein mass in these enzymes.We report the optical phonon shifts induced by phase transition effects of vanadium dioxide (VO2) in monolayer molybdenum disulfide (MoS2) when interfacing with a VO2 film showing a metal-insulator transition coupled with structural phase transition (SPT). To this end, the monolayer MoS2 directly synthesized on a SiO2/Si substrate by chemical vapor deposition was first transferred onto a VO2/c-Al2O3 substrate in which the VO2 film was prepared by a sputtering method. We compared the MoS2 interfaced with the VO2 film with the as-synthesized MoS2 by using Raman spectroscopy. The temperature-dependent Raman scattering characteristics exhibited the distinct phonon behaviors of the E2g1 and A1g modes in the monolayer MoS2. Specifically, for the as-synthesized MoS2, there were no Raman shifts for each mode, but the enhancement in the Raman intensities of E2g1 and A1g modes was clearly observed with increasing temperature, which could be interpreted by the significant contribution of the interface optical interference effect. In contrast, the red-shifts of both the E2g1 and A1g modes for the MoS2 transferred onto VO2 were clearly observed across the phase transition of VO2, which could be explained in terms of the in-plane tensile strain effect induced by the SPT and the enhancement of electron-phonon interactions due to an increased electron density at the MoS2/VO2 interface through the electronic phase transition. This study provides further insights into the influence of interfacial hybridization for the heterogeneous integration of 2D transition-metal dichalcogenides and strongly correlated materials.Bifunctional electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are necessary in the renewable energy systems. However, the kinetically slow and large energy-demanding procedures of oxygen electrocatalysis make the preparation of bifunctional catalysts difficult. In this work, we report a novel hierarchical GdFeO3 perovskite oxide of a spherelike nanostructure and surface modification with the group X heterometal oxides. The nanostructured GdFeO3 layer behaved as a bifunctional electrocatalyst in the oxygen electrocatalysis of OER and ORR. Moreover, the surface decoration with catalytically active PtO x + Ni/NiO nanoparticles enhanced the electrocatalytic performances substantially. Incorporation of mesoporous PtO x + Ni/NiO nanoparticles into the porous GdFeO3 nanostructure enlarged the electrochemically active surface area and provided the interconnected nanostructures to facilitate the OER/ORR. The nanostructures were visualized by scanning electron microscopy and transmission electron microscopy images, and the surface area and pore size of nanoparticles were analyzed from N2 adsorption/desorption isotherms. Tafel analysis indicates that surface modification effectively improves the kinetics of oxygen reactions and accordingly increases the electrocatalytic efficiency. Finally, the 2 wt % PtO x + NiO|GdFeO3 (x = 0, 1, and 2) electrode achieved the enhanced OER performance with an overpotential of 0.19 V at 10 mA/cm2 in an alkaline solution and a high turnover frequency of 0.28 s-1 at η = 0.5 V. Furthermore, the ORR activity is observed with an onset potential of 0.80 V and a half-wave potential (E1/2) of 0.40 V versus reversible hydrogen electrode.