Project description:Driving chemical transformations in dynamic thin films represents a rapidly thriving and diversifying research area. Dynamic thin films provide a number of benefits including large surface areas, high shearing rates, rapid heat and mass transfer, micromixing and fluidic pressure waves. Combinations of these effects provide an avant-garde style of conducting chemical reactions with surprising and unusual outcomes. The vortex fluidic device (VFD) has proved its capabilities in accelerating and increasing the efficiencies of numerous organic, materials and biochemical reactions. This Minireview surveys transformations that have benefited from VFD-mediated processing, and identifies concepts driving the effectiveness of vortex-based dynamic thin films.
Project description:The widespread use of silver nanoparticles (Ag-NPs) in consumer and medical products provides strong motivation for a careful assessment of their environmental and human health risks. Recent studies have shown that Ag-NPs released to the natural environment undergo profound chemical transformations that can affect silver bioavailability, toxicity, and risk. Less is known about Ag-NP chemical transformations in biological systems, though the medical literature clearly reports that chronic silver ingestion produces argyrial deposits consisting of silver-, sulfur-, and selenium-containing particulate phases. Here we show that Ag-NPs undergo a rich set of biochemical transformations, including accelerated oxidative dissolution in gastric acid, thiol binding and exchange, photoreduction of thiol- or protein-bound silver to secondary zerovalent Ag-NPs, and rapid reactions between silver surfaces and reduced selenium species. Selenide is also observed to rapidly exchange with sulfide in preformed Ag(2)S solid phases. The combined results allow us to propose a conceptual model for Ag-NP transformation pathways in the human body. In this model, argyrial silver deposits are not translocated engineered Ag-NPs, but rather secondary particles formed by partial dissolution in the GI tract followed by ion uptake, systemic circulation as organo-Ag complexes, and immobilization as zerovalent Ag-NPs by photoreduction in light-affected skin regions. The secondary Ag-NPs then undergo detoxifying transformations into sulfides and further into selenides or Se/S mixed phases through exchange reactions. The formation of secondary particles in biological environments implies that Ag-NPs are not only a product of industrial nanotechnology but also have long been present in the human body following exposure to more traditional chemical forms of silver.
Project description:Sustained or repeated exposure to sedating drugs such as alcohol triggers homeostatic adaptations in the brain that lead to the development of drug tolerance and dependence. These adaptations involve long-term changes in the transcription of drug-responsive genes as well as an epigenetic restructuring of chromosomal regions that is thought to signal and maintain the altered transcriptional state. Drug-induced epigenetic changes have been shown to be important in the long-term adaptation that leads to alcohol tolerance and dependence endophenotypes. A major constraint impeding progress is that alcohol produces a surfeit of changes in gene expression, most that may not make any meaningful contribution to the ethanol response under study. Here we used a novel genomic epigenetic approach to find genes relevant for functional alcohol tolerance by exploiting the commonalities of two chemically distinct drugs. In Drosophila melanogaster, ethanol and benzyl alcohol induce mutual cross-tolerance, indicating that they share a common mechanism for producing tolerance. We surveyed the genome-wide changes in histone acetylation that occur in response to these drugs. Each drug induces modifications in a large number of genes. The genes that respond similarly to either treatment, however, represent a subgroup enriched for genes important for the common tolerance response. Genes were functionally tested for behavioral tolerance to the sedative effects of ethanol and benzyl alcohol using mutant and inducible RNAi stocks. We identified a network of genes that are essential for the development of tolerance to sedation by alcohol.
Project description:Sustained or repeated exposure to sedating drugs such as alcohol triggers homeostatic adaptations in the brain that lead to the development of drug tolerance and dependence. These adaptations involve long-term changes in the transcription of drug-responsive genes as well as an epigenetic restructuring of chromosomal regions that is thought to signal and maintain the altered transcriptional state. Drug-induced epigenetic changes have been shown to be important in the long-term adaptation that leads to alcohol tolerance and dependence endophenotypes. A major constraint impeding progress is that alcohol produces a surfeit of changes in gene expression, most that may not make any meaningful contribution to the ethanol response under study. Here we used a novel genomic epigenetic approach to find genes relevant for functional alcohol tolerance by exploiting the commonalities of two chemically distinct drugs. In Drosophila melanogaster, ethanol and benzyl alcohol induce mutual cross-tolerance, indicating that they share a common mechanism for producing tolerance. We surveyed the genome-wide changes in histone acetylation that occur in response to these drugs. Each drug induces modifications in a large number of genes. The genes that respond similarly to either treatment, however, represent a subgroup enriched for genes important for the common tolerance response. Genes were functionally tested for behavioral tolerance to the sedative effects of ethanol and benzyl alcohol using mutant and inducible RNAi stocks. We identified a network of genes that are essential for the development of tolerance to sedation by alcohol. A total of six samples. Two H4Ac ChIP-chip biological replicates from heads of Drosophila (untreated, IP/input), two H4Ac ChIP-chip biological replicates from heads of Drosophila sedated with benzyl alcohol (IP_treated/IP_control), and two H4Ac ChIP-chip biological replicates from heads of Drosophila sedated with ethanol (IP_treated/IP_control) are included.
Project description:Heterogeneous catalysis of adsorbates on metallic surfaces mediated by plasmons has potential high photoelectric conversion efficiency and controllable reaction selectivity. Theoretical modeling of dynamical reaction processes enables in-depth analyses complementing experimental investigations. Especially for plasmon-mediated chemical transformations, light absorption, photoelectric conversion, electron-electron scattering, and electron-phonon coupling occur simultaneously on different timescales, making it very challenging to delineate the complex interplay of different factors. In this work, a trajectory surface hopping non-adiabatic molecular dynamics method is used to investigate the dynamics of plasmon excitation in an Au20-CO system, including hot carrier generation, plasmon energy relaxation, and CO activation induced by electron-vibration coupling. The electronic properties indicate that when Au20-CO is excited, a partial charge transfer takes place from Au20 to CO. On the other hand, dynamical simulations show that hot carriers generated after plasmon excitation transfer back and forth between Au20 and CO. Meanwhile, the C-O stretching mode is activated due to non-adiabatic couplings. The efficiency of plasmon-mediated transformations (∼40%) is obtained based on the ensemble average of these quantities. Our simulations provide important dynamical and atomistic insights into plasmon-mediated chemical transformations from the perspective of non-adiabatic simulations.
Project description:We have systematically searched for chemical changes that generate compounds with distinct biological activity profiles. For this purpose, activity profiles were generated for ∼42000 compounds active against human targets. Unique activity profiles involving multiple target proteins were determined, and all possible matched molecular pairs (MMPs) were identified for compounds representing these profiles. An MMP is defined as a pair of compounds that are distinguished from each other only at a single site such as an R group or ring system. For example, in an MMP, a hydroxyl group might be replaced by a halogen atom or a benzene ring by an amide group. From ∼37500 MMPs, more than 300 nonredundant chemical transformations were isolated that yielded compounds with distinct activity profiles. None of these transformations was found in pairs of compounds with overlapping activity profiles. These transformations were ranked according to the number of MMPs, the number of activity profiles, and the total number of targets that they covered. In many instances, prioritized transformations involved ring systems of varying complexity. All transformations that were found to switch activity profiles are provided to enable further analysis and aid in compound design efforts.
Project description:Artificial metalloenzymes (ArMs) comprise a synthetic metal complex in a protein scaffold. ArMs display performances combining those of both homogeneous catalysts and biocatalysts. Specifically, ArMs selectively catalyze non-natural reactions and reactions inspired by nature in water under mild conditions. In the past few years, the construction of ArMs that possess a genetically incorporated unnatural amino acid and the directed evolution of ArMs have become of great interest in the field. Additionally, biochemical applications of ArMs have steadily increased, owing to the fact that compartmentalization within a protein scaffold allows the synthetic metal complex to remain functional in a sea of inactivating biomolecules. In this review, we present updates on: 1) the newly reported ArMs, according to their type of reaction, and 2) the unique biochemical applications of ArMs, including chemoenzymatic cascades and intracellular/in vivo catalysis. We believe that ArMs have great potential as catalysts for organic synthesis and as chemical biology tools for pharmaceutical applications.
Project description:IntroductionChlorine dioxide (ClO2) is a safe and efficient bactericide with unique advantages in reducing foodborne illnesses, inhibiting microbial growth, and maintaining the nutritional quality of food. However, gaseous ClO2 is sensitive to heat, vibration, and light, which limits its application.MethodsIn this study, a ClO2 precursor-stabilized ClO2 aqueous solution was encapsulated by the double emulsion method, and a high-performance ClO2 self-releasing polyvinyl alcohol (PVA) film was prepared to investigate its performance and effect on blueberry quality during storage.ResultsThe self-releasing films had the best overall performance when the microcapsule content was 10% as the film's mechanical properties, thermal stability, and film barrier properties were significantly improved. The inhibition rates of Listeria monocytogenes and Escherichia coli were 93.69% and 95.55%, respectively, and the mycelial growth of Staphylococcus griseus was successfully inhibited. The resulting ClO2 self-releasing films were used for blueberry preservation, and an experimental study found that the ClO2 self-releasing antimicrobial film group delayed the quality decline of blueberries. During the 14-day storage period, no mold contamination was observed in the ClO2 self-releasing film group, and blueberries in the antibacterial film group had higher anthocyanin accumulation during the storage period.DiscussionResearch analysis showed that films containing ClO2 microcapsules are promising materials for future fruit and vegetable packaging.
Project description:Crystals of the title compound, C(12)H(8)N(2)·C(7)H(8)O(2), were obtained during cocrystallization experiments of a compound with two hydrogen-bond donors (2-hydroxy-benzyl alcohol) with another compound containing two hydrogen-bond acceptors (phenanthroline). Unexpectedly, the two mol-ecules do not form dimers with two O-H⋯N hydrogen bonds connecting the two mol-ecules. However, one of the hydr-oxy groups forms a bifurcated hydrogen bond to both phenanthroline N atoms, whereas the other hydr-oxy group forms an O-H⋯O hydrogen bond to a symmetry-equivalent 2-hydroxy-benzyl alcohol mol-ecule. In addition, the crystal packing is stabilized by π-π inter-actions between the two phenanthroline ring systems, with a centroid-centroid distance of 3.570 Å.
Project description:Spodumene concentrate from the Pilbara region in Western Australia was characterized by X-ray diffraction (XRD), Scanning Electron Microscope Energy Dispersive Spectroscopy (SEM-EDS) and Mineral Liberation Analysis (MLA) to identify and quantify major minerals in the concentrate. Particle diameters ranged from 10 to 200 microns and the degree of liberation of major minerals was found to be more than 90%. The thermal behavior of spodumene and the concentration of its polymorphs were studied by heat treatments in the range of 900 to 1050 °C. All three polymorphs of the mineral (α, γ and β) were identified. Full transformation of the α-phase was achieved at 975 °C and 1000 °C after 240 and 60 min treatments, respectively. SEM images of thermally treated concentrate revealed fracturing of spodumene grains, producing minor cracks initially which became more prominent with increasing temperature. Material disintegration, melting and agglomeration with gangue minerals were also observed at higher temperatures. The metastable γ-phase achieved a peak concentration of 23% after 120 min at 975 °C. We suggest 1050 °C to be the threshold temperature for the process where even a short residence time causes appreciable transformation, however, 1000 °C may be the ideal temperature for processing the concentrate due to the degree of material disintegration and α-phase transformation observed. The application of a first-order kinetic model yields kinetic parameters which fit the experimental data well. The resultant apparent activation energies of 655 and 731 kJ mol-1 obtained for α- and γ-decay, respectively, confirm the strong temperature dependence for the spodumene polymorph transformations.