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E. M. Belova N. G. Vais V. F. Sopin A. I. Kazakov Yu. I. Rubtsov G. B. Manelis G. N. Marchenko 《Russian Chemical Bulletin》1989,38(11):2244-2249
Complexing in the HNO3-CH2Cl2 system was confirmed tensimetrically. The kinetics of nitration of wood cellulose by the HNO3-CH2Cl2 mixture were investigated. A large part of the cellulose is nitrated in a first fast reaction in comparison to the HNO3-H2SO4 mixture with the same concentration of HNO3. The rate of the process is determined by the rate of diffusion of the HNO3, the rate of the process decreases more rapidly in the case of HNO3-CH2Cl2 than in the HNO3-H2SO4 mixture, which is probably due to the effect of CH2Cl2 on the diffusion coefficient of HNO3.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2445–2450, November, 1989. 相似文献
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The efficiency of the in-source collision-induced dissociation (in-source CID) technique for the structural characterization of microcystins (MCYSTs) was evaluated. Microcystins that did not contain arginine underwent facile fragmentation to produce characteristic product ions at relatively low cone voltage and could be fully characterized based on their mass spectra. On the other hand, cyclic peptides possessing arginine residues, such as MCYST-RR, -LR, -YR and nodularin, were considerably more stable under in-source CID conditions and required higher cone voltage to induce fragmentation. This behaviour is explained in terms of the mobile proton model for peptide fragmentation that can be used as an indication for the presence of arginine when unknown microcystins are analyzed. In-source CID was applied to the characterization of microcystins released into water from a Microcystis aeruginosa culture (UTCC299) (UTCC: University of Toronto Culture Collection of Algae and Cyanobacteria). Six microcystins were detected in extracts from UTCC299: I, [D-Asp(3)]MCYST-LR; II, MCYST-LR; III, isomer of MCYST-LR; IV, isomer of methyl MCYST-LR; V, [D-Asp(3), Glu(OCH(3))(6)]MCYST-LR; and VI, [D-Glu(OCH(3))(6)]MCYST-LR. In-source CID provided mass spectral patterns similar to those obtained by CID in the collision cell of the mass spectrometer but was more sensitive for the analysis of microcystins. 相似文献
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V. N. Kiryushov T. P. Aleksandrova L. I. Skvortsova A. A. Vais 《Journal of Analytical Chemistry》2011,66(2):201-206
Cyclic and direct voltammetry with linear potential sweep was used to study the potential difference of the anode and cathode
peaks for hydroquinone and metol in the cyclic voltammograms (CVA) of their individual solutions on the main factors affecting the reversibility of the electrochemical process on electrodes
of a graphite-epoxy composite (GEC), namely, the state of the surface of the indicator electrode, the pH of the buffer solution, and the mode of polarization.
The surface state of the GEC electrode was affected by its passivation in air for various periods of time; the reversibility
of the electrode process was judged by the difference between the anode and cathode potentials on the CVAs of hydroquinone
and metol. A correlation was found between the degree of reversibility and the difference of peak potentials for similar electrode
processes of hydroquinone and metol on the GEC electrode and other solid electrodes made of graphite materials and platinum. 相似文献
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Condensation reactions in the bandpass reaction cell or dynamic reaction cell (DRC) were used for the determination of actinides and lanthanides such as uranium, thorium, neodymium and praseodymium. These elements react with oxygen reagent gas in the dynamic reaction cell of the ELAN DRC II instrument to give mono- and/or dioxo cationic species (UO2+, ThO+, NdO+ and PrO+, respectively). Increasing the oxygen flow rate in the dynamic reaction cell leads to the rapid decrease of the singly charged metal ions accompanied by the fast increase in the intensity of the oxide ion. This phenomenon is used to improve considerably the sensitivity of ICP-MS instruments equipped with a dynamic reaction cell for actinides and lanthanides. Estimated detection limits (EDL) obtained in this work for uranium, thorium, neodymium-144 and praseodymium are 0.022, 1.0, 0.045, and 0.10 ng L–1, respectively. The detection limit for uranium measured in the standard (vented) mode of an ELAN DRC II was found to be 0.22 ng L–1, which is an order of magnitude higher compared to the pressurized mode. 相似文献
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Bence Paul Dominic J. Hare David P. Bishop Chad Paton Van Tran Nguyen Nerida Cole Megan M. Niedwiecki Erica Andreozzi Angela Vais Jessica L. Billings Lisa Bray Ashley I. Bush Gawain McColl Blaine R. Roberts Paul A. Adlard David I. Finkelstein John Hellstrom Janet M. Hergt Jon D. Woodhead Philip A. Doble 《Chemical science》2015,6(10):5383-5393
Metals have a number of important roles within the brain. We used laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to map the three-dimensional concentrations and distributions of transition metals, in particular iron (Fe), copper (Cu) and zinc (Zn) within the murine brain. LA-ICP-MS is one of the leading analytical tools for measuring metals in tissue samples. Here, we present a complete data reduction protocol for measuring metals in biological samples, including the application of a pyramidal voxel registration technique to reproducibly align tissue sections. We used gold (Au) nanoparticle and ytterbium (Yb)-tagged tyrosine hydroxylase antibodies to assess the co-localisation of Fe and dopamine throughout the entire mouse brain. We also examined the natural clustering of metal concentrations within the murine brain to elucidate areas of similar composition. This clustering technique uses a mathematical approach to identify multiple ‘elemental clusters’, avoiding user bias and showing that metal composition follows a hierarchical organisation of neuroanatomical structures. This work provides new insight into the distinct compartmentalisation of metals in the brain, and presents new avenues of exploration with regard to region-specific, metal-associated neurodegeneration observed in several chronic neurodegenerative diseases. 相似文献
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A method for the preparation of 2-amino(acetamido)pyrimidines by condensation of α,β-unsaturated carbonyl compounds with guanidine (acetylguanidine) was developed. 相似文献
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O. E. Vais S. G. Bochkarev V. Yu. Bychenkov 《Bulletin of the Lebedev Physics Institute》2016,43(1):12-15
The problem of nonlinear Thomson scattering of an ultrashort laser pulse on free electrons from a sharp focus is solved within the test particle approach. To describe the laser beam fields, an exact solution to the Helmholtz equation is used, which allows simulation of the electron dynamics and emission when the paraxial approximation is certainly inapplicable. Characteristics of attosecond electromagnetic pulses of secondary emission from test electrons during their motion near the laser focus are studied. 相似文献
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