共查询到20条相似文献,搜索用时 10 毫秒
1.
《International journal of mass spectrometry》1999,182(2-3):153-160
Five-coordinate Ni N-glycoside complexes, consisting of a single tridentate N-glycoside ligand and a bidentate dap ligand coordinated to a central Ni(II) ion, were synthesized for a series of diastereomeric monosaccharides. Following excitation of the precursor ions in a quadrupole ion trap, reproducibly distinct product ion spectra were obtained for each diastereomeric complex. Neutral losses resulted from cross-ring cleavages of the monosaccharide ring and/or losses of a bidentate dap ligand. Isotopic labeling studies confirmed which particular carbon centers were lost from the precursor ion as a result of the cross-ring cleavages. Synthesis of the Ni–N glycoside complex was achieved using as little as 21 μg of monosaccharide. Production of the representative five-coordinate precursor ion was obtained over a wide range of metal–ligand:monosaccharide molar ratios and product ion spectra remained reproducible over this range. 相似文献
2.
N. V. Aksenov H. Bruchertseifer G. Ya. Starodub G. K. Vostokin E. E. Tereshatov G. A. Bozhikov S. V. Shishkin S. N. Dmitriev 《Journal of Radioanalytical and Nuclear Chemistry》2009,279(1):341-343
A rapid method for the preparation of 87Y/87mSr radionuclide generator from a rubidium chloride target irradiated with 35 MeV α-particles is described. A simple two-step
procedure is used to obtain a carrier-free 87mSr isotope with a high enough radiochemical yield and high purity in the final aqueous fraction. 相似文献
3.
Hui-Jun Won Byambatseren Baigalmaa Jei-Kwon Moon Chong-Hun Jung Kune-Woo Lee Jae-Hyuk Hyun 《Journal of Radioanalytical and Nuclear Chemistry》2011,287(2):525-531
Type 304 stainless steel specimens artificially contaminated with CsCl solution were treated with KOH solution and KNO3 solution, respectively. Cs+ ion removal tests by a Q-switched Nd:YAG laser at 1064 nm at a given fluence of 57.3 J/cm2 were performed. The surface morphology and the relative atomic mole ratio of the specimen surface were investigated by SEM
and EPMA. The order of Cs+ ion removal efficiency of laser was no-treatment < KOH < KNO3 during the 42 shots. From the investigation of XPS peaks around 532.7 and 292.9 eV, KNO3 on a surface of specimen was found to be fully decomposed during the laser irradiation. It was suggested that Cs2O particulates formed by the reaction between the reactive oxygen generated from the nitrate ion and Cs+ ion on the metal surface could be easily suspended. For the KOH system, FeOOH was formed during the laser irradiation and
it changed into Fe2O3. It was also suggested that Cs2O particulates were formed by the reaction between the reactive oxygen generated from the decomposition of K2O and Cs+ ion on the metal surface.. 相似文献
4.
The radiation chemical redox transformations in solutions of bromides in the presence of minor additives of iodides were studied
by pulse radiolysis. The change in the concentrations of the Br− and I− ions changes the ratio of the formed short-lived radical anions Br2
·−, BrI·−, and I2
·−. The spectrum of the mixed radical anion BrI·− contains a broad optical band at 370 nm with ɛ370 = 9650 L mol−1 cm−1. The reduction potential of the BrI·−/Br−, I− pair is 1.25 V. The rate constants for the forward and backward reactions Br2
·− + I− ⇌ BrI·− + Br− are k
f = 4.3·109 and k
r = 1.0·105 L mol−1 s−1, respectively; for the reactions BrI·− ⇌ Br− + I·, k
f = 5.7·108 s−1 and k
r = 1.0·1010 L mol−1 s−1.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1787–1792, September, 2008. 相似文献
5.
Yan Li Hui-ling Liu Yan-bo Sun Zhuo Li Xu-ri Huang Chia-chung Sun 《Theoretical chemistry accounts》2009,124(5-6):409
A detailed theoretical study is carried out at the B3LYP/6-311G(d,p) and CCSD(T)/6-311++G(3df,2pd) (single-point) levels as an attempt to investigate the mechanism of the little understand ion–molecule reaction between HCN+ and NH3. Various possible reaction pathways are considered. It is shown that six dissociation products P 1 (NH3 + + HCN), P 2 (NH4 + + CN), P 3 (NH3 + + HNC), P 9 (HCNH+ + NH2) P 10 (NCNH3 + + H), and P 12 (HNCNH2 + + H) are both thermodynamically and kinetically feasible. Among these products, P 1 is the most competitive product with predominant abundance. P 3 and P 9 may be the second feasible products with comparable yields. P 12 may be the least possible product followed by the almost negligible P 2 and P 10 . Because the isomers and transition states involved in the HCN+ + NH3 reaction all lie below the reactant, the title reaction is expected to be rapid, which is consistent with the measured large rate constant in experiment. The title reaction may have a potential relevance in Titan’s atmosphere, where the temperature is very low. Furthermore, our calculated results are compared with the previous experimental findings. 相似文献
6.
Bouchonnet S Kinani S Sablier M 《European journal of mass spectrometry (Chichester, England)》2007,13(3):223-226
Users of ion trap mass spectrometers frequently develop methods that associate chemical ionization with tandem mass spectrometry detection. With apparatus using internal ionization, the chemical reagent is present in the trap during the collision induced dissociation (CID) step and one may wonder if the reagent influences the fragmentation ratios in MS/MS. We report a comparison of the fragmentation ratios of protonated molecules when using the most common reagents (methane, ammonia, methanol, acetonitrile, isobutane) for performing in situ chemical ionization. Four molecules were chosen in the medical field to serve as models: alprazolam, diazepam, flunitrazepam and acetaminophen. In the non-resonant CID mode, the influence of the reagent mass is clearly seen in spite of its low partial pressure in the ion trap; the reagent acts as a "heavy target": the degree of fragmentation increases with the molecular weight of the reagent. In the resonant CID mode, there is no evident correlation between the fragmentation ratio of MH(+) ions and the nature of the CI reagent; a slight shift of the secular frequency of the precursor ion, which tends to reduce the CID efficiency, could compensate for the "heavy target" effect underscored in the non-resonant mode. 相似文献
7.
Using three accurate potential energy surfaces of the 3A″, 3A′, and 1A′ states constructed recently, we present a quasi-classical trajectory (QCT) calculation for O + HCl (v = 0, j = 0) → OH + Cl reaction at the collision energies (E
col) of 14.0–20.0 kcal/mol. The three angular distribution functions—P(qr ) P(\theta_{r} ) , P(jr ) P(\varphi_{r} ) , and P(qr ,jr ) P(\theta_{r} ,\varphi_{r} ) , together with the four commonly used polarization-dependent differential cross-sections,
\frac2ps \fracds00 dwt , \frac2ps \fracds20 dwt , \frac2ps \fracds22 + dwt , \textand \frac2ps \fracds21 - dwt {\frac{2\pi }{\sigma }}\,{\frac{{d\sigma_{00} }}{{d\omega_{t} }}},\,{\frac{2\pi }{\sigma }}\,{\frac{{d\sigma_{20} }}{{d\omega_{t} }}},\,{\frac{2\pi }{\sigma }}\,{\frac{{d\sigma_{22 + } }}{{d\omega_{t} }}},\,{\text{and}}\,{\frac{2\pi }{\sigma }}\,{\frac{{d\sigma_{21 - } }}{{d\omega_{t} }}} are exhibited to get an insight into the alignment and the orientation of the product OH radical. There is a similar behavior
of the tendency scattering direction for the two triplet electronic states (3A″ and 3A′)—backward scattering dominates, however, forward scattering prevails for the case of 1A′ state. Also, obvious differences have been found in the stereo-dynamical information, which reveals the influences of the
potential energy surface and the collision energy. The degrees of polarization and the influence of the collision energy on
the stereo-dynamics characters of the title reaction are both demonstrated in the order of 3A′ > 3A″ > 1A′. 相似文献
8.
Potamitis C Matsoukas MT Tselios T Mavromoustakos T Golič Grdadolnik S 《Journal of computer-aided molecular design》2011,25(9):837-853
The two new synthetic analogues of the MBP83–99 epitope substituted at Lys91 (primary TCR contact) with Phe [MBP83–99 (Phe91)] or Tyr [MBP83–99 (Tyr91)], have been structurally elucidated using 1D and 2D high resolution NMR studies. The conformational analysis of the two
altered peptide ligands (APLs) has been performed and showed that they adopt a linear and extended conformation which is in
agreement with the structural requirements of the peptides that interact with the HLA-DR2 and TCR receptors. In addition,
Molecular Dynamics (MD) simulations of the two analogues in complex with HLA-DR2 (DRA, DRB1*1501) and TCR were performed.
Similarities and differences of the binding motif of the two analogues were observed which provide a possible explanation
of their biological activity. Their differences in the binding mode in comparison with the MBP83–99 epitope may also explain their antagonistic versus agonistic activity. The obtained results clearly indicate that substitutions
in crucial amino acids (TCR contacts) in combination with the specific conformational characteristics of the MBP83–99 immunodominant epitope lead to an alteration of their biological activity. These results make the rational drug design intriguing
since the biological activity is very sensitive to the substitution and conformation of the mutated MBP epitopes. 相似文献
9.
A. B. Azlarov Kh. M. Polvonov M. K. Askarova S. Tukhtaev 《Russian Journal of Inorganic Chemistry》2011,56(1):124-127
The solubility in the 2Na+,Mg2+‖2Cl−, 2ClO3−-H2O system was studied at 20 and 100°C and the solubility diagrams were plotted. New compounds were not found to form in the
title quaternary reciprocal system. The sodium chloride field was observed to expand with rising temperature. 相似文献
10.
T. S. Shestakova I. A. Khalymbadzha S. L. Deev O. S. Eltsov V. L. Rusinov Z. O. Shenkarev A. S. Arseniev O. N. Chupakhin 《Russian Chemical Bulletin》2011,60(4):729-732
Selective methods for the incorporation of stable isotopes 15N and 2H into the structure of antiviral medicine “triazavirine” 1 were developed. The synthesized isotopically modified “triazavirine” 1–
2
H
3
,
15
N
3
contained the labeled atoms in both the azole and the azine rings. 13C and 15N NMR spectra of the isotope-containing sample 1–
2
H
3
,
15
N
3
were thoroughly analyzed. 相似文献
11.
Conductometric and calorimetric titrations of Extremely Diluted Solutions (EDS) were performed by adding HCl or NaOH solutions.
The aim of this study is to obtain further confirmation of the hypothesized presence, in the EDS, of molecular aggregates
of water molecules. The measurements on the EDS evidenced some relevant differences compared to those on solutions with just
water as solvent. The conductivity and the pH caused by adding the titrant, namely NaOH or HCl, were markedly different to
those of the control solutions. We suppose that the preparation procedure of the EDS could produce non-equilibrium changes
in the supramolecular structure of water. The experimental results were interpreted by considering the interactions that can
take place between the OH− or H3O+ and the hypothesized molecular aggregates of water molecules i.e. dissipative structures. A comparison was made about the
nature of the driving force that leads to the formation of the complexes between the two ions deriving from probes and the
molecular aggregates of water molecules (dissipative structures). In this study, we have determined the thermodynamic parameters
of association between molecular aggregates of water molecules (dissipative structures) in the EDS and OH− or H3O+ probe ions. The experimental results were interpreted by considering a favorable interaction between the H3O+ and OH− ions and the dissipative structures, due, probably, to steric hindrance and chemical affinity with the aggregates. 相似文献
12.
Yu. I. Kostyukevich O. N. Kharybin A. S. Kononikhin I. A. Popov E. N. Nikolaev 《High Energy Chemistry》2016,50(3):165-170
The ultrahigh-resolution mass spectra of a substance P peptide labeled with deuterium have been obtained. The use of an ion trap with dynamic harmonization has made it possible to resolve the hyperfine isotopic structure of peaks and to reliably distinguish the hydrogen isotopes from the isotopes of carbon in the composition of the test molecules. The deuterium–hydrogen exchange reaction of humic acids has been performed in a gas phase, and it has been shown that the resolving power attained is sufficient for reliable interpretation of the results. 相似文献
13.
Abstract
First principle density-functional theory calculations have been carried out on the interaction of I− and I3 − with TiO2 anatase surfaces, modeled by finite clusters that range in size from 48 to 180 atoms. The total energy per TiO2 unit and the HOMO-LUMO gaps decrease with increasing the size of the clusters. Both redox species (I− and I3 −) are strongly adsorbed on the TiO2 surface with the adsorbtion of I− being stronger. Adsorption of triiodide leads to its dissociation. The positions of the HOMO and LUMO of the adsorbed systems shift negatively from their respective cluster values. Solvation effects have been modeled using the CPCM model. Introducing solvent reduces the shifting of HOMO and LUMO. Implications for dye-sensitized solar cells (DSSC) are discussed. Both the HOMO-LUMO shifting and the strong adsorption might affect the performance of the cell. 相似文献14.
Meyer MR Dinger J Schwaninger AE Wissenbach DK Zapp J Fritschi G Maurer HH 《Analytical and bioanalytical chemistry》2012,402(3):1249-1255
The opioid 3-methylfentanyl, a designer drug of the fentanyl type, was scheduled by the Controlled Substance Act due to its
high potency and abuse potential. To overcome this regulation, isofentanyl, another designer fentanyl, was synthesized in
a clandestine laboratory and seized by the German police. The aims of the presented study were to identify the phase I and
phase II metabolites of 3-methylfentanyl and isofentanyl in rat urine, to identify the cytochrome P450 (CYP) isoenzymes involved
in their initial metabolic steps, and, finally, to test their detectability in urine. Using liquid chromatography (LC)–linear
ion trap–mass spectrometry (MSn), nine phase I and five phase II metabolites of 3-methylfentanyl and 11 phase I and four phase II metabolites of isofentanyl
could be identified. The following metabolic steps could be postulated for both drugs: N-dealkylation followed by hydroxylation
of the alkyl and aryl moiety, hydroxylation of the propanamide side chain followed by oxidation to the corresponding carboxylic
acid, and, finally, hydroxylation of the benzyl moiety followed by methylation. In addition, N-oxidation of isofentanyl could
also be observed. All hydroxy metabolites were partly excreted as glucuronides. Using recombinant human isoenzymes, CYP2C19,
CYP2D6, CYP3A4, and CYP3A5 were found to be involved in the initial metabolic steps. Our LC-MSn screening approach allowed the detection of 0.01 mg/L of 3-methylfentanyl and isofentanyl in spiked urine. However, in urine
of rats after the administration of suspected recreational doses, the parent drugs could not be detected, but their common
nor metabolite, which should therefore be the target for urine screening. 相似文献
15.
É. B. Coropceanu A. P. Rija V. N. Shafranskii O. A. Bologa M. Gdaniec S. T. Malinovskii 《Journal of Structural Chemistry》2007,48(6):1110-1117
The complexes [Co(DH)2(Sam)2]2[ZrF6]·5H2O (I) and [Co(DH)2(Sam)2][BF4]·H2O (II), where DH? is the dimethylglyoxime monoanion, and Sam is para-aminobenzenesulfamide (sulfanilamide, white streptocid), were synthesized, and their crystal structures were determined by X-ray diffraction analysis. The coordination polyhedron of the Co3+ atom is an N6 octahedron formed by four nitrogen atoms of the two dimethylglyoxime residues and two nitrogen atoms of the Sam fragments. The latter are realized in virtually parallel orientation relative to the polyhedron of the metal atom and its equatorial plane; the average value of the dihedral angles is 26.8(1)°, and there is π-π interaction between the benzene rings of the Sam fragments and the π delocalized equatorial metallocycle. The deviation of the cobalt atom from the four-angle plane is up to 0.009(1) Å. The (Co-N)DH? and (Co-N)Sam distances in the [Co(DH)2(Sam)2]+ complex cations vary from 1.892(2) Å to 1.907(3) Å and from 2.000(2) Å to 2.012(2) Å, respectively. The [ZrF6]2? and [BF4]? complex anions play the major role in crystal formation; they produce a substantial effect on the formation of a complex system of hydrogen bonds. 相似文献
16.
Kellenbach E Sanders K Michiels PJ Girard FC 《Analytical and bioanalytical chemistry》2011,399(2):621-628
The recently revised European Pharmacopeia and US Pharmacopeia heparin sodium monographs include nuclear magnetic resonance
(NMR) tests on both identity and purity. In KMnO4-bleached heparin, an unidentified NMR signal is present at 2.10 ppm at a level of 15–20% of the mean of signal height of
the major glucosamine (GlcNAc/GlcNS,6S) anomeric proton signal at 5.42 ppm and of the major iduronic acid (IdoA2S) anomeric
proton signal at 5.21 ppm. According to the new monographs, no unidentified signals greater than 4% should be detected at
that position. Thus, the material did not meet the acceptance criterion. The signal at 2.10 ppm has been present at the same
level in all released MSD KMnO4-bleached heparin sodium batches analyzed over the past 10 years. The signal is a result of the KMnO4 bleaching. No (oversulfated) chondroitin sulfate or dermatan sulfate was detected in this material. A comprehensive NMR study
using long-range heteronuclear 2D techniques identifies this signal at 2.10 ppm as originating from the acetyl methyl group
of (6-sulfated) 2-N-acetyl-2-deoxy-glucono-1,5-lactone. This modified monosaccharide is formed by the KMnO4 oxidation of the reducing end of a terminal N-acetylglucosamine. 相似文献
17.
Arun Kumar NS Prashanth Shivappa Adarakatti Ashoka S Pandurangappa Malingappa 《Journal of Solid State Electrochemistry》2018,22(6):1711-1719
A simple strategy has been proposed to quantify Zn2+ ions using CeO2 nanoparticle-modified glassy carbon electrode. The CeO2 nanoparticles were prepared by sucrose-nitrate decomposition method, and it was characterized by X-ray diffraction (XRD), FT-IR, TEM, and surface area analyzer. The synthesized CeO2 nanoparticles were used as modifier molecules as a thin film on glassy carbon electrode (GCE) in the trace level quantification of Zn2+ by using cyclic voltammetry (CV) and differential pulse anodic stripping voltammetry (DPASV) techniques. The fabricated sensor exhibited a good analytical response towards Zn2+ ions. The modified electrode showed a wide linearity in the concentration range 20–380 μg L?1 with a limit of detection 0.36 μg L?1. The proposed electrochemical sensor was successfully applied to trace level Zn2+ quantification from real sample matrices. 相似文献
18.
A pure anatase phase nano-SO42− /TiO2 catalysts were synthesized and their catalytic activities were tested. Nano-SO42−/TiO2 shows high activity and effective re-usable when used as basic catalysts for the synthesis of dioctyl sebacate. 相似文献
19.
A new method for the possible incorporation of nuclear wastes has been attempted here by using ceramic matrix of TiO2 as a host precursor for confinement. Hafnium is used as a simulant for actinide high-level waste. After incorporating 181Hf tracer into TiO2 matrix, the leaching property of the resulting matrix was studied in water, sodium chloride and humic acid solutions. The
leaching was measured in each of the case by following the radioactivity of 181Hf. TiO2 matrix has also been exposed to γ-radiation in order to simulate the radiation field for nuclear waste. It has been investigated
with a nuclear technique called time differential perturbed Angular Correlation (TDPAC) that the lattice structure of titania
remains undisturbed even under a strong radiation field. The leaching of 181Hf has also been studied after irradiating the TiO2 matrix with γ-radiation and the leaching behavior was observed not to change from that before irradiation. 相似文献
20.
A. V. Ivanov S. A. Zinkin A. V. Gerasimenko O. N. Antzutkin W. Forsling 《Russian Journal of Coordination Chemistry》2007,33(1):20-31
Silver(I) complexes with four symmetrically substituted O,O′-dialkyl derivatives of dithiophosphoric acid of the general formula [Ag{S2P(OR)2}] n (R = C2H5, i-C3H7, C4H9, and s-C4H9) were obtained. Their structures and spectroscopic characteristics were studied by solid-state 13C and 31P CP/MAS NMR spectroscopy and X-ray diffraction analysis. The parameters of the anisotropy of the 31P chemical shift 31P-δ aniso and η (δ aniso is the chemical shift anisotropy and η is the asymmetry parameter) calculated from the diagrams of the x 2-statistic revealed that the (RO)2PS2 groups act as bridging ligands in all the silver(I) complexes obtained. The hexanuclear complex [Ag6{S2P(O-i-C3H7)2}6] was found to form two modifications α and β. According to the X-ray diffraction data, the silver(I) complex with O,O′-di-s-butyl dithiophosphate exists as discrete hexanuclear molecules [Ag6{S2P(O-s-C4H9)2}6]. In the clear molecules β-[Ag6{S2P(O-i-C3H7)2}6], the signals for the phosphorus atoms were assigned to their positions determined from the X-ray diffraction data. 相似文献