Guanine-rich DNA sequences can form G-quadruplexes stabilized by stacked G-G-G-G tetrads in monovalent cation-containing solution. The length and number of individual G-tracts and the length and ...sequence context of linker residues define the diverse topologies adopted by G-quadruplexes. The review highlights recent solution NMR-based G-quadruplex structures formed by the four-repeat human telomere in K⁺ solution and the guanine-rich strands of c-myc, c-kit and variant bcl-2 oncogenic promoters, as well as a bimolecular G-quadruplex that targets HIV-1 integrase. Such structure determinations have helped to identify unanticipated scaffolds such as interlocked G-quadruplexes, as well as novel topologies represented by double-chain-reversal and V-shaped loops, triads, mixed tetrads, adenine-mediated pentads and hexads and snap-back G-tetrad alignments. The review also highlights the recent identification of guanine-rich sequences positioned adjacent to translation start sites in 5'-untranslated regions (5'-UTRs) of RNA oncogenic sequences. The activity of the enzyme telomerase, which maintains telomere length, can be negatively regulated through G-quadruplex formation at telomeric ends. The review evaluates progress related to ongoing efforts to identify small molecule drugs that bind and stabilize distinct G-quadruplex scaffolds associated with telomeric and oncogenic sequences, and outlines progress towards identifying recognition principles based on several X-ray-based structures of ligand-G-quadruplex complexes.
•Innovative single-step SPS technique to fabricate close type IRS is suggested.•Non-dispersible Cs-containing cores for IRS were produced using cheap zeolite raw.•SPS regimes require low temperature ...and short time compared to conventional methods.•Obtained cores show exceptional characteristics meeting ISO standards.
The work presents a novel method for fabrication of the high-quality ionizing radiation source (IRS), which is promising to replace unsafe commercial products based on 137CsCl prohibited by IAEA. Spark plasma sintering (SPS) technique has been applied to produce dense ceramic and glass-ceramic matrixes from Cs-containing (˜13.5 wt.%) zeolite yielding in non-dispersible cores sealed in the container of radiation-resistant steel (J93503, US standard). One-stage SPS regimes to provide high-quality product have been optimized: sintering temperature <1000 °C, heating and holging duration 13 and 5 min, respectively, pressure 24.5 MPa. XRD, SEM, EDX, BET, XFS and solid-state MAS NMR 133Cs methods prove exceptional physico-chemical and mechanical characteristics of the obtained materials, namely: density 99.8% from theoretical, compressive strength ˜477 MPa, leaching rate 10−4–10−6 g cm−2 day−1. Results of the investigation can be promising for fabrication of the IRS cores on a large scale as done for similar Russian products RSL, IGI-C, M37C, GID-C.
Fe
x
Co
1−
x
WO
4
films on the titanium were formed by one-step plasma electrolytic oxidation in tungstate electrolytes containing Fe(II)-EDTA and/or Co(II)-EDTA anions. The resulting composites were ...investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS), diffuse reflection, and electrochemical impedance spectroscopy (EIS). All formed coatings contain TiO
2
in the anatase modification and orthorhombic WO
3
. The oxide layers obtained in a tungstate electrolyte with the addition of only Co(II)-EDTA ions also include CoWO
4
. Based on Mott–Schottky plots all samples show a positive slope, indicating the behavior of an n-type semiconductor. For the composites obtained, the values of the band gap determined by the Tauc method for direct allowed transitions are 2.5–2.9 eV. The resulting composites exhibit photocatalytic activity in the degradation of methyl orange (10 mg/L, pH 6.8, С(Н
2
О
2
) = 10 mmol/L) under UV and visible light irradiation. The highest MO degradation reaches 80% in the presence of Ti/W/Co composite under UV light. According to the Nyquist plots, the most active samples have the lowest resistance to charge transfer.
A new promising method for the synthesis of NASICON (Na
3
Zr
2
Si
2
PO
12
) by pyrolysis of organic solutions has been developed. Sodium oleate, zirconyl oleate, tributyl phosphate, and ...tetraethoxysilane have been used as precursors. The molar ratios of the components of the mixture for the formation of NASICON have been established. The effect of sodium on the formation of the zirconium dioxide phase has been proven. A finely dispersed material with an average grain size of 0.2 µm has been obtained. Changes in morphology and composition depending on the time and temperature of firing the sample are studied. The results have been confirmed by X-ray powder diffraction and scanning electron microscopy. To refine the parameters of the crystal lattice, a full-profile analysis has been performed by the Rietveld method. The process of obtaining NASICON takes about 9 h, i.e. it is the least time consuming of all the alternative ways of synthesis. The advantages of this method are the possibility of lowering the sintering temperature, the absence of the need to control many parameters during synthesis, and minimizing the duration and multi-stage process. The method contributes to the development and production of more promising ion-substituted structures.
Methods for the synthesis of radiopaque tantalum-containing glass and glass-ceramics by doping 45S5 bioglass with tantalum oxide are presented. Bioactive glass has been obtained by pyrolysis of a ...mixture of organic precursors: tetraethoxysilane, tributyl phosphate, sodium oleate, and calcium oleate. Bioglass has been doped with tantalum oxide by three different methods. The mechanism of suppression of the biological activity of materials with an increase in the Ta
2
O
5
content has been studied. The bioactivity of samples containing 1–40 wt % Ta
2
O
5
has been evaluated in vitro using a model medium—an SBF solution. The samples have been studied by
31
P NMR, XRD, SEM, and EDS. A decrease in the concentration of calcium in the glass phase due to the formation of insoluble CaTa
2
O
6
crystals has been considered the major cause of the suppression of the bioactivity of glasses. Samples containing up to 10 wt % Ta
2
O
5
can be used in modern medicine as materials that restore bone tissue. The radiopaque substance in the composition of the biomaterial makes it possible to monitor the process of bone tissue regeneration. Samples containing more than 20 wt % Ta
2
O
5
failed in vitro tests. Due to the dissolution of one of the phases of glass-ceramics in a model solution, the prognosis for the use of such materials in vivo is unfavorable.
The paper presents the results of studying mechanochemical synthesis of hafnium carbide in the process of vibration treatment of the mixture of powders of hafnium and amorphous carbon obtained by ...pyrolytic processing of plant materials. Phase compositions, morphology, as well as fractional and chemical compositions of the synthesized products were studied. It has been found that the use of carbon obtained from plant materials is beneficial for the mechanochemical synthesis of highly-dispersed hafnium carbide with low sulfur content.
The properties of zirconium ceramics can be improved by combination with calcium phosphate compounds, which impart bioactivity to the bioinert material. The effect of Ta
2
O
5
on some properties of ...ceramics was studied. Tantalum oxide doping increases the radiopacity of calcium phosphate zirconium ceramics, but deteriorates the mechanical and bioactive properties. This ceramics can be proposed as a material for replacing bone tissue defects. The material was shown to have sufficient strength, radiopacity, and developed microrelief and to contain a bioactive phase. The obtained materials meet conditions necessary for the replacement therapy. The method can be used to produce a material with specified characteristics for the manufacture of individual implants.
—The article presents data on the synthesis of nanostructured, X-ray amorphous lithium aluminosilicate, with a Si : Al ratio of 3 : 1. The composition, morphology, and thermal behavior were studied. ...The sorption isotherm of Cs
+
ions was obtained under static conditions with a ratio of T : L = 1 : 400. The maximum sorption capacity, degree of extraction, and distribution coefficients of cesium were determined. Data on the sorption kinetics of Cs
+
ions were obtained at temperatures 30 and 60°C, and the activation energy of the sorption process and diffusion coefficients were calculated.
Calcium aluminosilicates synthesized by chemical modification of nanostructured synthetic Na zeolites were characterized. The sorption properties were studied for calcium aluminosilicates with SiO
2
...: Al
2
O
3
ratios of 2 : 1, 4 : 1, 6 : 1, 8 : 1, and 10 : 1. The maximum capacity of these compounds to sorb Cs
+
ions under static conditions from solutions without salt background was shown to reach 1.45 mmol/g (192.7 mg/g). The results of this work allow one to consider these compounds as promising materials for the sorption and immobilization of long-lived radionuclides.
Manganese-doped anatase with a nanosized morphology (as spherically shaped nanoparticles) has been synthesized under hydrothermal conditions. It has been shown that manganese is incorporated into the ...titanium dioxide structure to form substitutional solid solutions. At high dopant concentrations, part of the introduced manganese goes to the formation of α-MnO
2
. A significant increase in the optical activity in the visible range and a decrease in the bandgap width down to ~2.4 eV are observed for manganese-doped anatase because of the appearance of extrinsic (multivalent Mn ions) and intrinsic compensating (oxygen vacancies) defects. It has been found that manganese-doped samples are diluted magnetic semiconductors, and the magnetic characteristics increase with increasing manganese content. All manganese-containing samples demonstrate photocatalytic activity in the degradation reaction of indigo carmine when irradiated with visible light. The degree of dye degradation depends on the content of manganese in the samples and reaches >90%.
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