Abstract
The article discusses the use of double frequency conversion in the receiving module of the radar. To solve the resulting interference in the feeder paths, it is proposed to use a fiber- ...optic transmission system. The results of experimental investigations are presented.
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•2-(1,2,4-triazol-3-yl)acetates and 5-amino-2,4-dihydropyrazol-3-ones were synthesized.•Heterocyclization involving the Pinner salts was applied at the key step.•Its regioselectivity ...depended on the nature of the intermediate carboxyimidates.•Mono- and bifunctional heterocyclic (spirocyclic) building blocks were prepared.
A series of 2-(1H-1,2,4-triazol-3-yl)acetates, as well as 4-mono- and 4,4-disubstituted 5-amino-2,4-dihydro-3H-pyrazol-3-ones (including spirocyclic derivatives) have been synthesized using the Pinner reaction strategy. α-Mono- and α,α-disubstituted ethyl cyanoacetates were converted into the corresponding carboxyimidate salts that served as the key intermediates. Their further reaction with formylhydrazide or hydrazine hydrate provided triazolylacetates or aminopyrazolones (including spirocyclic derivatives), depending on the structure of the starting Pinner salt and the nature of the nucleophile. The scope and limitations of the developed synthetic method have been established.
Phytases hydrolyse phytate (myo-inositol hexakisphosphate), the principal form of phosphate stored in plant seeds to produce phosphate and lower phosphorylated myo-inositols. They are used ...extensively in the feed industry, and have been characterised biochemically and structurally with a number of structures in the PDB. They are divided into four distinct families: histidine acid phosphatases (HAP), β-propeller phytases, cysteine phosphatases and purple acid phosphatases and also split into three enzyme classes, the 3-, 5- and 6-phytases, depending on the position of the first phosphate in the inositol ring to be removed. We report identification, cloning, purification and 3D structures of 6-phytases from two bacteria, Hafnia alvei and Yersinia kristensenii, together with their pH optima, thermal stability, and degradation profiles for phytate. An important result is the structure of the H. alvei enzyme in complex with the substrate analogue myo-inositol hexakissulphate. In contrast to the only previous structure of a ligand-bound 6-phytase, where the 3-phosphate was unexpectedly in the catalytic site, in the H. alvei complex the expected scissile 6-phosphate (sulphate in the inhibitor) is placed in the catalytic site.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The necessity of using spectral analysis to study the structure of the line of the nuclear magnetic resonance (NMR) signal recorded using the modulation technique has been substantiated. The ...specifics of its use in researching condensed media in both current and stationary states have been determined. It was found that it is necessary to use the discrete Fourier transform to construct the amplitude and phase spectra from the experimental NMR signal recorded from the medium under study, as well as from the absorption and dispersion signals calculated for this medium using the Bloch equations with new coefficients. A technique has been developed for comparing spectra from experimental and calculated NMR signals to determine the line structure. The research results are presented.
Structure-based virtual ligand screening is emerging as a key paradigm for early drug discovery owing to the availability of high-resolution target structures
and ultra-large libraries of virtual ...compounds
. However, to keep pace with the rapid growth of virtual libraries, such as readily available for synthesis (REAL) combinatorial libraries
, new approaches to compound screening are needed
. Here we introduce a modular synthon-based approach-V-SYNTHES-to perform hierarchical structure-based screening of a REAL Space library of more than 11 billion compounds. V-SYNTHES first identifies the best scaffold-synthon combinations as seeds suitable for further growth, and then iteratively elaborates these seeds to select complete molecules with the best docking scores. This hierarchical combinatorial approach enables the rapid detection of the best-scoring compounds in the gigascale chemical space while performing docking of only a small fraction (<0.1%) of the library compounds. Chemical synthesis and experimental testing of novel cannabinoid antagonists predicted by V-SYNTHES demonstrated a 33% hit rate, including 14 submicromolar ligands, substantially improving over a standard virtual screening of the Enamine REAL diversity subset, which required approximately 100 times more computational resources. Synthesis of selected analogues of the best hits further improved potencies and affinities (best inhibitory constant (K
) = 0.9 nM) and CB
/CB
selectivity (50-200-fold). V-SYNTHES was also tested on a kinase target, ROCK1, further supporting its use for lead discovery. The approach is easily scalable for the rapid growth of combinatorial libraries and potentially adaptable to any docking algorithm.
A rare gold–telluride montbrayite from the large Svetlinsk gold–telluride deposit (South Urals, Russia) was comprehensively studied using optical microscopy, scanning electron microscopy, electron ...microprobe analysis, reflectance measurements, electron backscatter diffraction, and Raman spectroscopy. Significant variations in the composition of the mineral were revealed (in wt%): Au 36.98–48.66, Te 43.35–56.53, Sb 2.49–8.10, Ag up to 4.56, Pb up to 2.04, Bi up to 0.33, Cu up to 1.42. There are two distinct groups with much more-limited variation within the observed compositional interval (in wt%): (1) Au 36.98–41.22, Te 49.35–56.53, Sb 2.49–5.57; (2) Au 47.86–48.66, Te 43.35–44.92, Sb 7.15–8.10. The empirical formula calculated on the basis of 61 apfu is Au16.43–23.28Sb1.79–6.09Te32.01–38.89Ag0–3.69Bi0–0.14Pb0–0.90Cu0–1.96. Two substitution mechanisms for antimony are proposed in the studied montbrayite grains: Sb→Au (2.5–5.6 wt% Sb) and Sb→Te (7–8 wt% Sb). The dependence of the reflection spectra and Raman spectra on the antimony content and its substitution mechanism, respectively, was found in the mineral. The slope of the reflectance spectra decreases and the curve in the blue–green region of the spectrum disappears with increasing Sb content in montbrayite. Raman spectra are reported for the first time for this mineral. The average positions of the peak with high-intensity are ~64 cm−1 and ~90 cm−1 for montbrayite with Sb→Te and Sb→Au, respectively. Two grains of montbrayite demonstrate decomposition according to two schemes: (1) montbrayite (7 wt% Sb) → native gold + calaverite ± altaite, and (2) montbrayite (5 wt% Sb) → native gold + tellurantimony ± altaite. A combination of melting and dissolution–precipitation processes may be responsible for the formation of these decomposition textures.
In this paper one of several directions of caesium atomic clock modernisation is presented. This paper deals with theoretical model which takes into account features of the development of magnetic ...field stabilization system for caesium atomic clock and describes the affect of this stabilization system on frequency stability of caesium atomic clock. New magnetic field stabilization system allows eliminating one of the most important perturbing factors affecting on long-term frequency stability. Experimental research of the caesium atomic clock's metrological characteristics with magnetic field stabilization system showed improvement long-term frequency stability on 10%.
The recently discovered CRISPR-Cas gene editing system and its derivatives have found numerous applications in fundamental biology research and pharmaceutical sciences. The need for precise external ...control over the gene editing and regulatory events has driven the development of inducible CRISPR-Cas systems. While most of the light-controllable CRISPR-Cas systems are based on protein engineering, we developed an alternative synthetic approach based on modification of crRNA/tracrRNA duplex (guide RNA or gRNA) with photocaging groups, preventing the gRNA from recognizing its genome target sequence until its deprotection is induced within seconds of illumination. This approach relies on a straightforward solid-phase synthesis of the photocaged gRNAs, with simpler purification and characterization processes in comparison to engineering a light-responsive protein. We have demonstrated the feasibility of photocaging of gRNAs and light-mediated DNA cleavage upon brief exposure to light in vitro. We have achieved light-mediated spatiotemporally resolved gene editing as well as gene activation in cells, whereas photocaged gRNAs showed virtually no detectable gene editing or activation in the absence of light irradiation. Finally, we have applied this system to spatiotemporally control gene editing in zebrafish embryos in vivo, enabling the use of this strategy for developmental biology and tissue engineering applications.
The paper presents the genetic characteristics of two strains of spring viraemia of carp virus (SVCV), Kirov/08 and Orenburg/14, isolated in the Kirov and Orenburg oblasts of the Russian Federation, ...respectively. Nucleotide sequence analysis of a 516-bp fragment of the G genes of Kirov/08 and Orenburg/14 showed 9.5% divergence. Phylogenetic analysis demonstrated a close relationship of these strains to SVCV isolates recovered in Russia, Ukraine, and the Republic of Moldova.
The problems of monitoring the state of flowing media with a simultaneous change in temperature and flow rate of the medium by more than two orders of magnitude are considered. A design of a ...flow-through refractometer is proposed for monitoring the state of transparent media in laminar and turbulent flow regimes, as well as at high flow rates and changes in the temperature of the medium by more than 200°C. The developed flow-through refractometer implements a method for measuring the refractive index, based on the principle of parallelism of two beams: the incident and transmitted through a pipeline with refraction at the boundaries of several media. The piping in the form of a cylindrical Plexiglas insert is part of the refractometer design. The design of the optical part of the refractometer with a vertical section of the pipeline eliminates the influence on the measurement of the refractive index of errors caused by multiple reflections of laser radiation from optical elements, the formation of voids or vortex flows in the pipeline. For the proposed refractometer there are no restrictions on the value of the measured refractive index of the flowing liquid, in contrast to the previously used industrial flow-through refractometers, the principle of operation of which is based on the phenomenon of total internal reflection of laser radiation at the interface of two media. The results of experimental studies of various media with the proposed refractometer are presented.
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