Core-shell nanocatalyst activities are chiefly controlled by bimetallic material composition, shell thickness, and nanoparticle size. We present a machine learning framework predicting strain with site-specific precision to rationalize how strain on Pt core-shell nanocatalysts can enhance oxygen reduction activities. Large compressive strain on Pt@Cu and Pt@Ni induces optimal mass activities at 1.9 nm nanoparticle size. It is predicted that bimetallic Pt@Au and Pt@Ag have the best mass activities at 2.8 nm, where active sites are exposed to weak compressive strain. https://www.selleckchem.com/products/4-Methylumbelliferone(4-MU).html We demonstrate that optimal strain depends on the nanoparticle size; for instance, strengthening compressive strain on 1.92 nm sized Pt@Cu and Pt@Ni, or weakening compressive strain on 2.83 nm sized Pt@Ag and Pt@Au, can lead to further enhanced mass activities.An organocatalyzed enantioselective γ-elimination process has been achieved and applied in the kinetic resolution of peroxides to access chiral peroxides and epoxides. The reaction provided a pathway for the preparation of two useful synthetic and biologically important structural motifs through a single-step reaction. A range of substrates has been resolved with a selectivity factor up to 63. The obtained enantioenriched peroxides and epoxides allowed a series of transformations with retained optical purities.Inverse-electron demand Diels-Alder cycloadditions have emerged as important bioorthogonal reactions in chemical biology. Understanding and predicting reaction rates for bioconjugation reactions is fundamental for evaluating their efficacy in biological systems. Here, we present multivariate models to predict the second order rate constants of bioorthogonal inverse-electron demand Diels-Alder reactions involving 1,2,4,5-tetrazines derivatives. A data-driven approach was used to model these reactions by parametrizing both the dienophiles and the dienes partners. The models are statistically robust and were used to predict/extrapolate the outcome of several reactions as well as to identify mechanistic differences among similar reactants.High-valent Ni complexes have proven to be good platforms for diverse cross-coupling reactions that are otherwise difficult to be achieved with conventional low-valent catalysts. However, their reductive elimination (RE) activities are still significantly variable by up to 5 orders of magnitude, depending on the supporting ligand and oxidation state of the Ni center. To elucidate frontier molecular orbitals (FMOs) that determine the RE activity of the Ni center, the electronic structures of cycloneophyl (CH2C(CH3)2-o-C6H4) NiIII and NiIV complexes have been characterized by utilizing various transition metal-based spectroscopic techniques such as electronic absorption, magnetic circular dichroism, electron paramagnetic resonance, resonance Raman, and X-ray absorption spectroscopies. In combination with density functional theory computations, the spectroscopic analyses have shown that the energies of the C-to-Ni charge-transfer (CT) electronic transitions are strongly correlated to the rates of C-C bond-forming RE reaction. This correlation suggests that the kinetic barrier of the RE reaction is determined by energy cost for internal CT (ICT) from the coordinated carbon moiety to the Ni center, and that FMOs involved in the RE reaction and the C-to-Ni CT electronic transitions are essentially identical. This FMO determination has led us to discover that photoexcitation to the C-to-Ni CT excited states accelerates the C-C cross-coupling reaction by up to 105 times, as the CT electronic transition can substitute for the rate-determining ICT step of the RE reaction at the ground electronic state.β-Tryptase, a homotetrameric serine protease, has four identical active sites facing a central pore, presenting an optimized setting for the rational design of bivalent inhibitors that bridge two adjacent sites. Using diol, hydroxymethyl phenols or benzoyl methyl hydroxamates, and boronic acid chemistries to reversibly join two [3-(1-acylpiperidin-4-yl)phenyl]methanamine core ligands, we have successfully produced a series of self-assembling heterodimeric inhibitors. These heterodimeric tryptase inhibitors demonstrate superior activity compared to monomeric modes of inhibition. X-ray crystallography validated the dimeric mechanism of inhibition, and compounds demonstrated high selectivity against related proteases, good target engagement, and tryptase inhibition in HMC1 xenograft models. Screening 3872 possible combinations from 44 boronic acid and 88 diol derivatives revealed several combinations that produced nanomolar inhibition, and seven unique pairs produced greater than 100-fold improvement in potency over monomeric inhibition. These heterodimeric tryptase inhibitors demonstrate the power of target-driven combinatorial chemistry to deliver bivalent drugs in a small molecule form.We developed the first acceptorless dehydrogenation of aliphatic secondary alcohols to ketones under visible light irradiation at room temperature by devising a ternary hybrid catalyst system comprising a photoredox catalyst, a thiophosphate organocatalyst, and a nickel catalyst. The reaction proceeded through three main steps hydrogen atom transfer from the α-C-H bond of an alcohol substrate to the thiyl radical of the photo-oxidized organocatalyst, interception of the generated carbon-centered radical with a nickel catalyst, and β-hydride elimination. The reaction proceeded in high yield under mild conditions without producing side products (except H2 gas) from various alcohols, including sterically hindered alcohols, a steroid, and a pharmaceutical derivative. This catalyst system also promoted acceptorless cross-dehydrogenative esterification from aldehydes and alcohols through hemiacetal intermediates.There are currently increased efforts to determine potential sources of trace metal contaminants in the food supply. While there are likely many sources of these elements, processing of foods has gained attention as one such route. Research is reviewed on how processing aids used for food production, including beverage filtration and fining, have been targeted as potential sources of trace metals. Potential remediation methods to reduce elemental transfer occurring during processing is discussed. While food processing aids are often a critical part of food manufacturing, they can be a potential source of trace metal contaminants, including heavy metals.
Core-shell nanocatalyst activities are chiefly controlled by bimetallic material composition, shell thickness, and nanoparticle size. We present a machine learning framework predicting strain with site-specific precision to rationalize how strain on Pt core-shell nanocatalysts can enhance oxygen reduction activities. Large compressive strain on Pt@Cu and Pt@Ni induces optimal mass activities at 1.9 nm nanoparticle size. It is predicted that bimetallic Pt@Au and Pt@Ag have the best mass activities at 2.8 nm, where active sites are exposed to weak compressive strain. https://www.selleckchem.com/products/4-Methylumbelliferone(4-MU).html We demonstrate that optimal strain depends on the nanoparticle size; for instance, strengthening compressive strain on 1.92 nm sized Pt@Cu and Pt@Ni, or weakening compressive strain on 2.83 nm sized Pt@Ag and Pt@Au, can lead to further enhanced mass activities.An organocatalyzed enantioselective γ-elimination process has been achieved and applied in the kinetic resolution of peroxides to access chiral peroxides and epoxides. The reaction provided a pathway for the preparation of two useful synthetic and biologically important structural motifs through a single-step reaction. A range of substrates has been resolved with a selectivity factor up to 63. The obtained enantioenriched peroxides and epoxides allowed a series of transformations with retained optical purities.Inverse-electron demand Diels-Alder cycloadditions have emerged as important bioorthogonal reactions in chemical biology. Understanding and predicting reaction rates for bioconjugation reactions is fundamental for evaluating their efficacy in biological systems. Here, we present multivariate models to predict the second order rate constants of bioorthogonal inverse-electron demand Diels-Alder reactions involving 1,2,4,5-tetrazines derivatives. A data-driven approach was used to model these reactions by parametrizing both the dienophiles and the dienes partners. The models are statistically robust and were used to predict/extrapolate the outcome of several reactions as well as to identify mechanistic differences among similar reactants.High-valent Ni complexes have proven to be good platforms for diverse cross-coupling reactions that are otherwise difficult to be achieved with conventional low-valent catalysts. However, their reductive elimination (RE) activities are still significantly variable by up to 5 orders of magnitude, depending on the supporting ligand and oxidation state of the Ni center. To elucidate frontier molecular orbitals (FMOs) that determine the RE activity of the Ni center, the electronic structures of cycloneophyl (CH2C(CH3)2-o-C6H4) NiIII and NiIV complexes have been characterized by utilizing various transition metal-based spectroscopic techniques such as electronic absorption, magnetic circular dichroism, electron paramagnetic resonance, resonance Raman, and X-ray absorption spectroscopies. In combination with density functional theory computations, the spectroscopic analyses have shown that the energies of the C-to-Ni charge-transfer (CT) electronic transitions are strongly correlated to the rates of C-C bond-forming RE reaction. This correlation suggests that the kinetic barrier of the RE reaction is determined by energy cost for internal CT (ICT) from the coordinated carbon moiety to the Ni center, and that FMOs involved in the RE reaction and the C-to-Ni CT electronic transitions are essentially identical. This FMO determination has led us to discover that photoexcitation to the C-to-Ni CT excited states accelerates the C-C cross-coupling reaction by up to 105 times, as the CT electronic transition can substitute for the rate-determining ICT step of the RE reaction at the ground electronic state.β-Tryptase, a homotetrameric serine protease, has four identical active sites facing a central pore, presenting an optimized setting for the rational design of bivalent inhibitors that bridge two adjacent sites. Using diol, hydroxymethyl phenols or benzoyl methyl hydroxamates, and boronic acid chemistries to reversibly join two [3-(1-acylpiperidin-4-yl)phenyl]methanamine core ligands, we have successfully produced a series of self-assembling heterodimeric inhibitors. These heterodimeric tryptase inhibitors demonstrate superior activity compared to monomeric modes of inhibition. X-ray crystallography validated the dimeric mechanism of inhibition, and compounds demonstrated high selectivity against related proteases, good target engagement, and tryptase inhibition in HMC1 xenograft models. Screening 3872 possible combinations from 44 boronic acid and 88 diol derivatives revealed several combinations that produced nanomolar inhibition, and seven unique pairs produced greater than 100-fold improvement in potency over monomeric inhibition. These heterodimeric tryptase inhibitors demonstrate the power of target-driven combinatorial chemistry to deliver bivalent drugs in a small molecule form.We developed the first acceptorless dehydrogenation of aliphatic secondary alcohols to ketones under visible light irradiation at room temperature by devising a ternary hybrid catalyst system comprising a photoredox catalyst, a thiophosphate organocatalyst, and a nickel catalyst. The reaction proceeded through three main steps hydrogen atom transfer from the α-C-H bond of an alcohol substrate to the thiyl radical of the photo-oxidized organocatalyst, interception of the generated carbon-centered radical with a nickel catalyst, and β-hydride elimination. The reaction proceeded in high yield under mild conditions without producing side products (except H2 gas) from various alcohols, including sterically hindered alcohols, a steroid, and a pharmaceutical derivative. This catalyst system also promoted acceptorless cross-dehydrogenative esterification from aldehydes and alcohols through hemiacetal intermediates.There are currently increased efforts to determine potential sources of trace metal contaminants in the food supply. While there are likely many sources of these elements, processing of foods has gained attention as one such route. Research is reviewed on how processing aids used for food production, including beverage filtration and fining, have been targeted as potential sources of trace metals. Potential remediation methods to reduce elemental transfer occurring during processing is discussed. While food processing aids are often a critical part of food manufacturing, they can be a potential source of trace metal contaminants, including heavy metals.
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