The synthesis of various polybenzimidazoles (PBIs) in condensation media such as polyphosphoric acid and Eaton’s reagent was accomplished. Molecular weight distribution of the synthesized polymers ...was examined with respect to the process conditions and the chemical structure of the monomers. It was found that during the synthesis of PBIs a side acylation reaction occurs which leads to the formation of branched macromolecules with Mw up to 2.3 × 106 and higher and even crosslinking, resulting in gelation of the polymers during synthesis. Fraction of the side reaction in the overall process appeared to be dependant on both the chemical structure of the monomers and the condensation media used. The orientation of the acylation reaction was determined by quantum-mechanical calculations.
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The catalyst H3+xPMo12−x+6Mox+5O40 supported on SiO2 was developed for peroxidation of 1,3‐ and 1,5‐diketones with hydrogen peroxide with the formation of bridged 1,2,4,5‐tetraoxanes and bridged ...1,2,4‐trioxolanes (ozonides) with high yield based on isolated products (up to 86 and 90 %, respectively) under heterogeneous conditions. Synthesis of peroxides under heterogeneous conditions is a rare process and represents a challenge for this field of chemistry, because peroxides tend to decompose on the surface of a catalyst . A new class of antifungal agents for crop protection, that is, cyclic peroxides: bridged 1,2,4,5‐tetraoxanes and bridged ozonides, was discovered. Some ozonides and tetraoxanes exhibit a very high antifungal activity and are superior to commercial fungicides, such as Triadimefon and Kresoxim‐methyl. It is important to note that none of the fungicides used in agricultural chemistry contains a peroxide fragment.
Being better: A heterogeneous catalyst was developed for the peroxidation of 1,3‐ and 1,5‐diketones with hydrogen peroxide with the formation of bridged 1,2,4,5‐tetraoxanes and bridged 1,2,4‐trioxolanes with yield up to 86 and 90 %, respectively. A new class of antifungal agents for crop protection, that is, cyclic peroxides, was discovered. Some ozonides and tetraoxanes exhibit a very high antifungal activity and are superior to commercial fungicides.
In recent years, the number of pollinators in the world has significantly decreased. A possible reason for this is the toxic effects of agrochemicals reducing the immunity of insects that leads to ...their increased susceptibility to pathogens.
is a dangerous entomopathogenic fungus, afflicting both honeybees and bumblebees. We investigated fungicide activity of cyclic synthetic peroxides against
isolated from
L. The peroxides exhibited high mycelium growth inhibition of
up to 94-100% at concentration 30 mg/L. EC
values were determined for the most active peroxides. Two peroxides showed higher antifungal activity against
than the commercial fungicide Triadimefon. The studied peroxides did not reduce the ability of bumblebees to fly and did not lead to the death of bumblebees. A new field of application for peroxides was disclosed.
Alkene ozonolysis is mostly known as a textbook reaction, resulting in carbonyl compounds. The combination of ozone and hydroperoxide was found to lead to the construction of more oxygen-rich ...compounds, unsymmetrical geminal bisperoxides, avoiding as well further oxidation with ozone, hydroperoxide, and oxygen as peroxide rearrangements. The discovered three-component synthesis provided alkylperoxy hydroperoxides in 41–63% yield from alkenes.
Organic peroxides are an important class of compounds for organic synthesis, pharmacological chemistry, materials science, and the polymer industry. Here, for the first time, we summarize the main ...achievements in the synthesis of organic peroxides by the action of Lewis acids and heteropoly acids. This review consists of three parts: (1) metal-based Lewis acids in the synthesis of organic peroxides; (2) the synthesis of organic peroxides promoted by non-metal-based Lewis acids; and (3) the application of heteropoly acids in the synthesis of organic peroxides. The information covered in this review will be useful for specialists in the field of organic synthesis, reactions and processes of oxygen-containing compounds, catalysis, pharmaceuticals, and materials engineering.
Four heteroatoms dance in the cascade of four pericyclic reactions initiated by ozonolysis of CN bonds. Switching from imines to semicarbazones introduces the fifth heteroatom that slows this dance, ...delays reaching the thermodynamically favorable escape path, and allows efficient interception of carbonyl oxides (Criegee intermediates, CIs) by an external nucleophile. The new three-component reaction of alcohols, ozone, and oximes/semicarbazones greatly facilitates synthetic access to monoperoxyacetals (alkoxyhydroperoxides).
The labile zinc pool in plant cells Zlobin, Ilya E; Kartashov, Alexander V; Nosov, Alexander V ...
Functional plant biology : FPB,
01/2019, Letnik:
46, Številka:
9
Journal Article
Recenzirano
Zinc is the most abundant and important transition metal in plants; however, the dynamic aspects of zinc homeostasis in plant cells are poorly understood. In this study we explored the pool of labile ...exchangeable zinc complexes in plant cells, and the potential influence of changes in intracellular zinc availability on cellular physiology. Work was performed on cultivated cell extracts of Arabidopsis thaliana (L.) Heynh. and Thellungiella salsuginea (Pall.) O.E. Schulz grown under control (3.48 µM Zn2+), 10-fold Zn excess or Zn starvation conditions. The free and labile Zn contents in the extracts were then determined by fluorimetric titration. We observed for the first time that plant cells contain micromolar concentrations of labile zinc complexes that account for a low percentage of the total zinc content. Labile zinc is mainly protein bound. Zn starvation inhibits cell proliferation and leads to the disappearance of the labile zinc pool, whereas Zn excess drastically increases the labile zinc pool. Free Zn2+ is buffered at picomolar concentrations in the intracellular milieu, and the increase in free Zn2+ concentrations to low nanomolar values clearly modulates enzyme activity by direct reversible binding. Such increases in free Zn2+ can be achieved by the substantial influx of additional zinc or by the oxidation of zinc-binding thiols. The observed features of the labile zinc pool in plant cells suggest it has a role in intracellular zinc trafficking and zinc signalling.
Callus and suspension cell cultures were successfully developed from
Sutherlandia frutescens
(Fabaceae), an endemic medicinal plant of South Africa. Two callus cell lines, originating from hypocotyl ...and cotyledon explants of in vitro seedlings under both dark and light conditions, showed intensive fresh weight accumulation with growth index ranging from 4.6 to 5.9. Suspension cell cultures induced from two callus lines had similar growth profiles and their growth index (15–18), specific growth rate (0.15–0.16 day
−1
), productivity (0.83–0.96 g/(l day)) and maximum biomass accumulation (16–18 g/l) remained relatively high for Fabaceae cell cultures during 27 sub-cultivations. Callus and suspension cell cultures showed similar profiles of secondary metabolites that were, however, different from leaves of greenhouse plants. Isoflavones were predominant in both callus and suspension cell cultures while flavonoids (sutherlandins) and triterpene glycosides of the cycloartane group (sutherlandiosides) were mostly found in leaves. Nineteen fatty acids (FA), both short- and very-long-chained (up to C
25:0
), were found in cell cultures. Linoleic and α-linolenic FA together comprised 60–64% out of total FA content in cell cultures followed by palmitic acid (18–25%). Extracts of suspension cell biomass exhibited antimicrobial activity against
Staphylococcus aureus
but were not effective against
Pseudomonas aeruginosa.
To the best of our knowledge, this is the first report on the induction, phytochemical composition and antimicrobial activity screening of
S. frutescens
suspension cell cultures which opens the door for their biotechnological application.
Extreme ultraviolet (EUV) lithography is expected to succeed in 193-nm immersion multi-patterning technology for sub-10-nm critical layer patterning. In order to be successful, EUV lithography has to ...demonstrate that it can satisfy the industry requirements in the following critical areas: power, dose stability, etendue, spectral content, and lifetime. Currently, development of second-generation laser-produced plasma (LPP) light sources for the ASML’s NXE:3300B EUV scanner is complete, and first units are installed and operational at chipmaker customers. We describe different aspects and performance characteristics of the sources, dose stability results, power scaling, and availability data for EUV sources and also report new development results.
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