The pyridinium oximes are known esterolytic agents, usually classified in the literature as catalysts, which mimic the catalytic mode of hydrolases. Herein, we combined kinetic and computational ...studies of the pyridinium-4-oxime-mediated acetylthiocholine (AcSCh
) hydrolysis to provide novel insights into their potential catalytic activity. The
-methyl- and
-benzylpyridinium-4-oximes have been tested as oximolytic agents toward the AcSCh
, while the newly synthesized
-acetyl-
-methylpyridinium-4-oxime iodide was employed for studying the consecutive hydrolytic reaction. The relevance of the AcSCh
hydrolysis as a competitive reaction to AcSCh
oximolysis was also investigated. The reactions were independently studied spectrophotometrically and rate constants,
,
and
, were evaluated over a convenient pH-range at
= 0.1 M and 25 °C. The catalytic action of pyridinium-4-oximes comprises two successive stages, acetylation (oximolysis) and deacetylation stage (pyridinium-4-oxime-ester hydrolysis), the latter being crucial for understanding the whole catalytic cycle. The complete mechanism is presented by the free energy reaction profiles obtained with (CPCM)/M06-2X/6-311++G(2df,2pd)//(CPCM)/M06-2X/6-31+G(d) computational model. The comparison of the observed rates of AcSCh
oximolytic cleavage and both competitive AcSCh
and consecutive pyridinium-4-oxime-ester hydrolytic cleavage revealed that the pyridinium-4-oximes cannot be classified as non-enzyme catalyst of the AcSCh
hydrolysis but as the very effective esterolytic agents.
A series of molybdenum(VI) complexes with aryl-functionalized alkyl dihydrazones was prepared by the reaction of MoO2(acac)2 and the appropriate dihydrazone in methanol. Their solid-state structures ...were elucidated via single-crystal X-ray diffraction (SC-XRD) and Fourier-transform infra-red (FTIR) spectroscopy, while the thermal stability of compounds was inspected by combined thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) experiments. The behaviour of complexes in DMSO-d6 solution was explored by nuclear magnetic resonance (NMR). The relevant data show that all complexes are dinuclear, with dihydrazones acting as ditopic hexadentate ligands. The in vitro cytotoxic activity of the prepared molybdenum(VI) complexes was evaluated on THP-1 and HepG2 cell lines, while their antibacterial activity was tested against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Moraxella catarrhalis bacteria. The majority of compounds proved to be non-cytotoxic, while some exhibited superior antibacterial activity in comparison to dihydrazone ligands.
It is known that the temperature of crystallization during the synthesis of
zeolite is one of the most important process parameters. However, during the
research work on the synthesis of zeolite 13X ...and the introduction of this
material into regular industrial production, it was noticed that the heating
rate of the starting reaction suspension can have an equally important
influence. This influence can be so pronounced that a difference of just a
few minutes in reaching the crystallization temperature can make a
significant difference in product quality, affect the presence of other
phases in the crystal, or even determine the direction of zeolite
crystallization. Therefore, the aim of this work was to show the influence
of the heating rate on the quality of the obtained 13X zeolite powders. The
obtained samples were analysed in terms of crystallinity (by X-ray
diffraction), chemical composition, granulometry and specific surface area
(by Brunauer-Emmett-Teller analysis), and regarding water and CO2 adsorption
capacities. Additionally, scanning electron microscopy analysis of the
samples showed the morphological characteristics of different 13X zeolite
powders. The analysis results of the obtained powders confirmed the
influence of the heating rate and helped to define the optimal synthesis
parameters i.e. the initial temperature and heating time, that resulted in
stable product quality.
The aim of this research was to determine the influence of the SiO
2
/Al
2
O
3
molar ratio on the specific commercial properties of NaA zeolite subtypes as final market products (4A,4A-AG and 4A-MS) ...under the real production and process conditions. The value of the SiO
2
/Al
2
O
3
molar ratio, so-called silicate module, was set as independently variable and the effect on the physical and chemical properties of each of the subtypes of NaA zeolites was examined.
The paper investigates how the SiO
2
/Al
2
O
3
molar ratio affects specific properties of NaA powders, namely the ion exchange capacity, oil adsorption capacity and water adsorption capacity. Some previous theoretical and experimental studies have shown that the molar ratio plays a crucial role in the formation of these very similar but for final application different subtypes of NaA zeolite. The experimental part of this work was performed and tested in real production conditions, which can be considered as an advantage in relevance to the obtained results. Various analytical and instrumental testing methods were used for the analysis of the obtained powders, including SEM, XRD and PSD analyses.
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•Na+,K+-ATPase activity alternates with freeze-thaw cycles.•Na+,K+-ATPase changes membrane microlocation between lipid rafts and bulk membrane.•Na+,K+-ATPase redistribution is ...accompanied by reshuffling of specific gangliosides.•Ganglioside GM1 distribution reflects Na+,K+-ATPase protein distribution.•GD1a, GD1b and GT1b distribution mirrors the changes in Na+,K+-ATPase activity.
A series of aryl-functionalized alkyl dihydrazones was prepared by condensation of succinyl or adipoyl dihydrazide and selected ortho-hydroxybenzaldehydes (2-hydroxybenzaldehyde, ...2-hydroxy-1-naphthaldehyde, 2,3-dihydroxybenzaldehyde, and 2,4-dihydroxybenzaldehyde) in solution. The obtained products were structurally characterized in the solid state by single-crystal X-ray diffraction (SC-XRD), thermal analysis (TGA-DSC), and Fourier transform infrared (FTIR) spectroscopy and in DMSO-d6 solution by nuclear magnetic resonance (NMR) techniques. Combined FTIR and crystal structure data point to a N–NH–C=O tautomeric form of the hydrazone parts as well as the enol-imino tautomeric form of the aldehyde residues and a robust trans-syn conformation for the structurally investigated ones. While the molecules retain the same tautomeric form in the DMSO-d6 solution, they adopt several conformations, due to rotations around Car–C, C–N, and N–N bonds. The compounds show exceptional thermal stability, with a complex degradation pattern. Slight differences in thermal behavior correlate to alkyl chain length and aryl substituents. The in vitro cytotoxic activity of prepared dihydrazones was evaluated on THP-1 and HepG2 cell lines, while their antibacterial activity was tested against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Moraxella catarrhalis bacteria. All compounds proved to be non-cytotoxic, and some exhibited moderate antibacterial activity.
Lipid rafts, membrane microdomains enriched with (glyco)sphingolipids, cholesterol, and select proteins, act as cellular signalosomes. Various methods have been used to separate lipid rafts from bulk ...(non‐raft) membranes, but most often, non‐ionic detergent Triton X‐100 has been used in their isolation. However, Triton X‐100 is a reported disruptor of lipid rafts. Histological evidence confirmed raft disruption by Triton X‐100, but remarkably revealed raft stability to treatment with a related polyethylene oxide detergent, Brij O20. We report isolation of detergent‐resistant membranes from mouse brain using Brij O20 and its use to determine the distribution of major mammalian brain gangliosides, GM1, GD1a, GD1b and GT1b. A different distribution of gangliosides—classically used as a raft marker—was discovered using Brij O20 versus Triton X‐100. Immunohistochemistry and imaging mass spectrometry confirm the results. Use of Brij O20 results in a distinctive membrane distribution of gangliosides that is not all lipid raft associated, but depends on the ganglioside structure. This is the first report of a significant proportion of gangliosides outside raft domains. We also determined the distribution of proteins functionally related to neuroplasticity and known to be affected by ganglioside environment, glutamate receptor subunit 2, amyloid precursor protein and neuroplastin and report the lipid raft populations of these proteins in mouse brain tissue. This work will enable more accurate lipid raft analysis with respect to glycosphingolipid and membrane protein composition and lead to improved resolution of lipid–protein interactions within biological membranes.
Using a data‐driven partitioning strategy, we report that a significant proportion of gangliosides, long believed to be lipid raft resident, reside outside raft domains. Immunohistochemistry and imaging mass spectrometry revealed that the distribution of gangliosides remains largely unchanged by treatment with Brij O20 detergent compared to the widely used Triton X‐100, which induces ganglioside redistribution. Lipid raft analyses of Brij O20 brain extracts revealed that gangliosides are not all lipid raft depending on the ganglioside structures. Likewise, different neuroplasticity protein raft distributions were revealed. This work enables more accurate lipid raft analyses for resolution of lipid–protein interactions in biological membranes.
Introduction/purpose: Bauxite residue as a waste product from the aluminium industry produced through the Bayer process is mainly composed of iron oxide, titanium oxide, silicon oxide and undissolved ...alumina together with a wide range of other oxides and a minor content of rare earth elements, gallium, vanadium and scandium, which vary according to the country of origin of the bauxite. The extraction of valuable elements from bauxite residues and the minimisation of bauxite residues during different treatments are an open research field. Methods: Different hydrometallurgical and pyrometallurgical methods were used for the treatment of bauxite residues. In this study, the results of the hydrometallurgical treatment of bauxite residue from Alumina Zvornik using sulfuric acid and hydrochloric acid will be shown in order to study the change of the mineralogical composition. Leaching efficiency will be calculated using the ICP OES analysis. The XRD-Analysis was used for the characterization of the initial material and solid residues studying the change of the mineralogical phases. Results: Leaching of bauxite residues with sulphuric and hydrochloric acid leads partially to the change of mineralogical structure and the transfer of elements into a liquid phase. Natural precipitation of iron is observed over time. Silica gel formation is confirmed during leaching of bauxite residues with hydrochloric acid. Conclusion: A new research strategy for treating bauxite residue is needed in order to ensure a complete change of the initial minearlogical structure and the most efficient transfer of metals into a liquid phase.
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•Mechanochemically accelerated vapour–assisted aging in the synthesis of (poly)oxalatomolybdates.•Transformation kinetics of the amorphous intermediates into the crystalline ...products.•In situ reaction monitoring by PXRD.
Mechanochemically accelerated vapour–assisted aging and transformation from the amorphous precipitate by aging to the crystalline products were demonstrated to be the efficient methods to synthesize crystalline hydrate and non-hydrate (poly)oxalatomolybdates, Co(NO2)(NH3)5MoO3(ox)H2O·H2O, Co(NH3)62Mo4O11(ox)4(H2O)·6H2O, Co(NH3)64Mo4O8(μ-O)4(ox)4MoO3(ox)(H2O)2·10H2O, Co(en)34MoO2(μ-O)(ox)2MoO3(ox)(H2O)2·7H2O and Co(ox)(en)22Mo2O5(ox)2(H2O)2·4H2O, respectively. We have also studied the transformation kinetics of the amorphous intermediates into the final crystalline oxalatomolybdates in an aqueous slurry at room temperature by in situ powder X-ray diffraction (PXRD) method coupled with numerical methods. Using the principal component analysis, PXRD data tensors were reduced to only one principal component. Reaction profiles were built and total times for completion were determined.
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