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51.
Midon M Gimadutdinow O Meiss G Friedhoff P Pingoud A 《Chembiochem : a European journal of chemical biology》2012,13(5):713-721
The His-Asn-His (HNH) motif characterizes the active sites of a large number of different nucleases such as homing endonucleases, restriction endonucleases, structure-specific nucleases and, in particular, nonspecific nucleases. Several biochemical studies have revealed an essential catalytic function for the first amino acid of this motif in HNH nucleases. This histidine residue was identified as the general base that activates a water molecule for a nucleophilic attack on the sugar phosphate backbone of nucleic acids. Replacement of histidine by an amino acid such as glycine or alanine, which lack the catalytically active imidazole side chain, leads to decreases of several orders of magnitude in the nucleolytic activities of members of this nuclease family. We were able, however, to restore the activity of HNH nuclease variants (i.e., EndA (Streptococcus pneumoniae), SmaNuc (Serratia marcescens) and NucA (Anabaena sp.)) that had been inactivated by His→Gly or His→Ala substitution by adding excess imidazole to the inactive enzymes in vitro. Imidazole clearly replaces the missing histidine side chain and thereby restores nucleolytic activity. Significantly, this chemical rescue could also be observed in vivo (Escherichia coli). The in vivo assay might be a promising starting point for the development of a high-throughput screening system for functional EndA inhibitors because, unlike the wild-type enzyme, the H160G and H160A variants of EndA can easily be produced in E. coli. A simple viability assay would allow inhibitors of EndA to be identified because these would counteract the toxicities of the chemically rescued EndA variants. Such inhibitors could be used to block the nucleolytic activity of EndA, which as a surface-exposed enzyme in its natural host destroys the DNA scaffolds of neutrophil extracellular traps (NETs) and thereby allows S. pneumoniae to escape the innate immune response. 相似文献
52.
Jarian Vernimmen Vera Meynen Myrjam Mertens Oleg I. Lebedev Gustaaf Van Tendeloo Pegie Cool 《Journal of Porous Materials》2012,19(2):153-160
Based on a facile one-pot templating synthesis, using a TS-1 zeolite recipe whereby part of the zeolite structure directing
agent is replaced by a mesopore templating agent, a trimodal material is formed. The resulting meso-TSM material combines
mesoporosity (Ti-MCM-41) with zeolitic features (TS-1) and a unique sheet-like morphology with uniform macroporous voids (macroholes).
Moreover, the macrohole formation, mesoporosity and zeolitic properties of the meso-TSM material can be controlled in a straightforward
way by adjusting the length of the hydrothermal treatment. This newly developed material may imply great potential for catalytic
redox applications and diffusion limitated processes because of its highly tunable character in all three dimensions (micro-,
meso- and macroporous scale). 相似文献
53.
Iana A. Minich Oleg I. Silyukov Liliia D. Kulish Irina A. Zvereva 《Ceramics International》2019,45(2):2704-2709
A protonated form of the n?=?4 layered bismuth containing perovskite-like titanate K2.5Bi2.5Ti4O13 belonging to Ruddlesden-Popper phases was prepared via ion exchange reaction of interlayer K+ with protons. Its composition was investigated by TG ICP and EDX analysis was found to be H2K0.5Bi2.5Ti4O13·H2O. The thermal behavior of the obtained phase was investigated by STA coupled with mass-spectrometry, the structural changes, happening with the sample during heating, were examined by XRD. It was shown that the as-prepared hydrated phase undergoes two-stage dehydration at low temperatures (up to 160?°C). The further heating leads to the gradual decomposition and crystallization of new phases, notably Bi2Ti2O7, Bi4Ti3O12 and Bi2Ti4O11. The morphology of the as-prepared sample and samples after heat treatment was examined using SEM. 相似文献
54.
V. V. Murav’ev L. V. Volkova A. V. Platunov V. A. Kulikov 《Russian Journal of Nondestructive Testing》2016,52(7):370-376
Experimental results of measuring mechanical stresses in R65 rails with the use of the acoustic elasticity effect and an electromagnetic-acoustic method for the input-reception of shear waves are presented. Results of modeling compressive stresses in a rail segment are provided. The experimental results are compared with theoretical estimates for stresses that are induced in a restrained rail by the temperature action. The results of monitoring residual stresses in rails are described for a segment of continuous welded rails. 相似文献
55.
Freddy Romm Valeria Karchevsky Oleg Figovsky 《Journal of surfactants and detergents》2000,3(4):475-481
Quaternary ammonium silicate is a surfactant with very high content of silica that allows its use for preparation of protective
coatings. The problem of silica aggregation from quaternary ammonium solution in limited volume is the focus of this paper.
The system is described by a model based on a Monte Carbo approach with thermodynamic limitations. Thermodynamic characteristics
are estimated by statistical polymer method. The model is employed for estimation of such properties as monomer concentration
and tortuosity. The results of computer simulation are used for forecasting properties of coatings and for practical preparation
of samples coated with quaternary ammonium silicate-based composition. 相似文献
56.
Vitalina M. Nikitina Oksana V. Nesterova Vladimir N. Kokozay Viktoriya V. Dyakonenko Oleg V. Shishkin Julia Jezierska 《Inorganic chemistry communications》2009,12(2):101-104
The one-pot self-assembly reaction of copper powder, Reineckes salt, acetone and tris(2-aminoethyl)amine (tren) in dmso affords to obtain a heterometallic compound [Cu(trenac)][Cr(NCS)4(NH3)2](NCS) · 6dmso with novel Schiff-base ligand N-(2-{[(1E)-3-amino-1,3-dimethylbutylidene]amino}ethyl)-N-(2-aminoethyl)ethane-1,2-diamine (trenac). The ligand trenac is generated by metal-directed condensation of tren, acetone and ammonia, formed during the synthetic procedure. X-ray structural investigations showed that the complex consists of [Cu(trenac)]2+ cations, anions of the Reineckes salt [Cr(NCS)4(NH3)2]?, uncoordinated thiocyanate groups and dmso molecules, which are held together by electrostatic forces and hydrogen-bonded interactions. The compound was characterized by EPR spectroscopic and magnetic susceptibility measurements. 相似文献
57.
Electronic and structural properties of antiphase boundaries in group III-V semiconductor compounds have been receiving increased attention due to the potential to integration of optically-active III-V heterostructures on silicon or germanium substrates. The formation energies of {110}, {111}, {112}, and {113} antiphase boundaries in GaAs and GaP were studied theoretically using a full-potential linearized augmented plane-wave density-functional approach. Results of the study reveal that the stoichiometric {110} boundaries are the most energetically favorable in both compounds. The specific formation energy γ of the remaining antiphase boundaries increases in the order of γ{113} ≈ γ{112} < γ{111}, which suggests {113} and {112} as possible planes for faceting and annihilation of antiphase boundaries in GaAs and GaP. 相似文献
58.
Iryna Govbakh Vitalii Kyryk Alina Ustymenko Volodymyr Rubtsov Oleg Tsupykov Nataliya V. Bulgakova Danylo O. Zavodovskiy Inna Sokolowska Andriy Maznychenko 《International journal of molecular sciences》2021,22(21)
Impaired motor and sensory functions are the main features of Charcot–Marie–Tooth disease. Mesenchymal stem cell (MSCs) therapy is one of the possible treatments for this disease. It was assumed that MSCs therapy can improve the contractile properties of the triceps surae (TS) muscles in mice with hereditary peripheral neuropathy. Murine adipose-derived mesenchymal stromal cells (AD-MSCs) were obtained for transplantation into TS muscles of FVB-C-Tg(GFPU)5Nagy/J mice. Three months after AD-MSCs transplantation, animals were subjected to electrophysiological investigations. Parameters of TS muscle tension after intermittent high frequency electrical sciatic nerve stimulations were analyzed. It was found that force of TS muscle tension contraction in animals after AD-MSCs treatment was two-time higher than in untreated mice. Normalized values of force muscle contraction in different phases of electrical stimulation were 0.3 ± 0.01 vs. 0.18 ± 0.01 and 0.26 ± 0.03 vs. 0.13 ± 0.03 for treated and untreated animals, respectively. It is assumed that the two-fold increase in TS muscle strength was caused by stem cell therapy. Apparently, AD-MSCs therapy can promote nerve regeneration and partial restoration of muscle function, and thus can be a potential therapeutic agent for the treatment of peripheral neuropathies. 相似文献
59.
将Al-5Mg-0.18Mn-0.2Sc-0.08Zr-0.01Fe-0.01Si(质量分数,%)合金铸锭进行多向等温锻造(应变12)或等径角挤压(应变10,325℃),再进行热轧(325℃)和冷轧(20℃),对比研究合金变形后的组织和力学行为.结果表明,对(亚)晶粒尺寸dUFG=2μm的超细晶组织合金进行多向等温锻造... 相似文献
60.
Oleg A. Mezentsev Rixin Zhu Richard E. DeVor Shiv G. Kapoor William A. Kline 《International Journal of Machine Tools and Manufacture》2002,42(4)
A model-based method for fault detection in tapping based on torque and radial forces is proposed. The method allows the identification of faults typical of a tapping operation including axial misalignment, tap runout, tooth breakage both singly and together. The validation experiments have been run on aluminum 356 workpieces for different combinations of process faults. Results have shown that the model predictions are in good agreement with the experimental radial force and torque signals under various fault conditions. 相似文献