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1.
Alireza Fattahi Behrooz Zekavat Touradj Solouki 《Journal of the American Society for Mass Spectrometry》2010,21(3):358-369
Electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) combined with H/D exchange
reactions was utilized to explore the existence of different b5+ and b4+ fragment ion conformers/isomers of hexapeptide WHWLQL in the gas phase. Distinct H/D exchange trends for protonated WHWLQL
([M + H]+) and its b5+ and b4+ fragment ions (with ND3) were observed. Isolated 12Call isotopomers of both b5+ and b4+ fragment ions yielded bimodal distributions of H/D exchanged product ions. The H/D exchange reaction kinetics also confirmed
that b5+ and b4+ fragment ions exist as combination of slow-exchanging (“s”) and fast-exchanging (“f”) species. The calculated rate constant
for the first labile hydrogen exchange of [M + H]+ (k[M + H]
+ = 3.80 ± 0.7 × 10−10 cm3 mol−1 s−1) was ∼30 and ∼5 times greater than those for the “s” and “f” species of b5+, respectively. Data from H/D exchange of isolated “s” species at longer ND3 reaction times confirmed the existence of different conformers or isomers for b5+ fragment ions. The sustained off-resonance irradiation collision-activated dissociation (SORI-CAD) of WHWLQL combined with
the H/D exchange reactions indicate that “s” and “f” species of b5+ and b4+ fragment ions can be produced in the ICR cell as well as the ESI source. The significance of these observations for detailed
understanding of protein sequencing and ion fragmentation pathways is discussed. 相似文献
2.
The rate constants of the reactions of the chlorine atom with C3F7I (k
1) and CF3I (k
2) have been measured using the resonance fluorescence of chlorine atoms in a flow reactor at 295 K: k
1 = (5.2 ± 0.3) × 10−12 cm3 molecule−1 s−1 and k
2 = (7.4 ± 0.6) × 10−13 cm3 molecule−1 s−1. No iodine atoms have been detected in the reaction products. 相似文献
3.
V. Yu. Rudyak V. G. Avakyan V. B. Nazarov N. I. Voronezheva 《Russian Chemical Bulletin》2006,55(8):1337-1345
The structures and energies of formation of α-cyclodextrin (α-CD) dimers formed according to the “head-to-head” (HH), “head-to-tail”
(HT), and “tail-to-tail” (TT) modes, harmonic vibrational frequencies, and intensities of IR bands of the IR transitions were
calculated by the DFT/PBE density functional method with full geometry optimization without symmetry restrictions. The spectral
data were transformed into spectral patterns. An α-CD molecule can exist in two isomeric forms close in energy, namely, α-CD− and α-CD+, with different directions of the ring intramolecular hydrogen bonds. Among the three α-CD− dimers, the highest dimerization energy (E
d/kcal mol−1) belongs to the HH− (68.9), TT− (43.4), and HT− (24.8) dimers. The strength of the α-CD+ dimers decreases in the series: TT+ (56.7), HT+ (49.4), and HH+ (42.4). The energies E
H of hydrogen bonds were calculated from the low-frequency shifts of bands of stretching vibrations of the OH groups involved
in the formation of these hydrogen bonds. The E
H value for each dimer correlates with E
d. A possibility of formation of intermolecular hydrogen bonds is a driving force of association of α-CD molecules in aqueous
solutions.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1289–1296, August, 2006. 相似文献
4.
Near-infrared and mid-infrared spectra of three tellurite minerals have been investigated. The structures and spectral properties
of copper bearing xocomecatlite and tlapallite are compared with an iron bearing rodalquilarite mineral. Two prominent bands
observed at 9,855 and 9,015 cm−1 are assigned to 2B1g → 2B2g and 2B1g → 2A1g transitions of Cu2+ ion in xocomecatlite. The cause of spectral distortion is the result of many cations of Ca, Pb, Cu and Zn in the tlapallite
mineral structure. Rodalquilarite is characterised by ferric ion absorption in the range 12,300–8,800 cm−1. Three water vibrational overtones are observed in xocomecatlite at 7,140, 7,075 and 6,935 cm−1 whereas in tlapallite bands are shifted to lower wavenumbers at 7,135, 7,080 and 6,830 cm−1. The complexity of rodalquilarite spectrum increases with the number of overlapping bands in the near-infrared. The observation
of intense absorption feature near 7,200 cm−1 confirms hydrogen bonding water molecules in xocomecatlite. Weak bands observed near 6,375 and 6,130 cm−1 in tellurites are attributed to the hydrogen bonding between (TeO3)2− and H2O. A number of overlapping bands at low wave numbers 4,800–4,000 cm−1 are caused by combinational modes of tellurite ion. (TeO3)2− stretching vibrations are characterised by three main absorptions at ~1,070, 780 and 665 cm−1.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
5.
Electrochemistry of hydrofullerene C60H36 was studied by cyclic voltammetry in THF and CH2Cl2 in the −47–14 °C temperature range. Hydrofullerene undergoes reversible one-electron reduction to form a radical anion in
THF (E
0=−3.18 V (Fc0/Fc+), Fc=ferrocene) and irreversible one-electron oxidation in CH2Cl2 (E
p
a
=1.22 V (Fc0/Fc+)). The reduction potential was used to estimate electron affinity of hydrofullerene as EA=−0.33 eV. It was suggested that
C60H36 is an isomer withT-symmetry in which 12 double bonds form four isolated benzenoid rings located in vertices of an imaginary inscribed tetrahedron
on the molecular surface. For hydrofullerene, the “electrochemical gap” is an analog of the energy gap (HOMO−LUMO), equal
to (E
Ox−E
Red)=4.4 V, and indicates that C60H36 is a sufficiently “hard” molecule with a low reactivity in redox reactions.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2083–2087, November, 1999. 相似文献
6.
A. P. Kilimov M. A. Svechnikova V. I. Shevchenko V. V. Smirnov F. V. Kvasnyuk-Mudryi S. B. Zotov 《Chemistry of Heterocyclic Compounds》1967,3(2):467-471
Data for the characteristic bands of cyclic ethers are reviewed. The infrared spectra of a number of 2-mono- and 2, 5-di-substituted
derivatives of tetrahydrofuran are investigated. Absorption bands at about 900 cm−1 are related to pulsation vibrations, and those at about 1200 cm−1 to antisymmetric skeletal vibrations, of the tetrahydrofuran ring. It is shown that to confirm the presence of a tetrahydrofuran
ring in a molecule, it is necessary to take into account not only the band of valence antisymmetric vibrations of the group
C-O-C (ν
C-O-C
as
1075 cm−1), but also bands due to ring pulsation vibrations (ring symmetric valence vibrations ν
sk
s
∼ 900 cm1). 相似文献
7.
G. F. Khudorozhko I. P. Asanov L. N. Mazalov P. P. Samoilov V. E. Fedorov 《Journal of Structural Chemistry》1994,34(4):505-508
Investigating changes in the charged state of atoms upon superconductivity-suppressing substitutions is one of the methods
to examine a relationship between the electronic structure of HTSC materials and the transition temperature to the superconducting
state. In this paper, we measured Ebnd of the inner levels of Ba atoms in Co- and Zn-doped YBa2Cu3O7−δ by X-ray photoelectron spectroscopy. Upon copper substitution by Co and Zn atoms, Ebnd of the inner levels diminishes for Ba atoms but remains the same for Cu and O atoms. The change of Ebnd of the inner levels of Ba atoms is attributed to the change of the Fermi level position in the “anionic” sublattice of (Cu3O7−δ)7−.
Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 4, pp. 91–95, July–August, 1994.
Translated by L. Smolina 相似文献
8.
The Cu–ZnO catalyst precursors with variable Cu:Zn ratio, between Zn-rich and Cu-rich compositions have been investigated
by a combination of electronic and vibrational spectroscopy. Synthesized catalyst precursors exhibit two d–d transition bands
of Cu2+ ions in a distorted octahedral symmetry, at 7,600 and 12,900 cm−1 (1,315 and 775 nm). The effect of structural cation substitution (Zn2+ and Cu2+) on band shifts is observed in the spectra of the synthetic catalyst precursors. The observation of two broad features at
∼7,600 and 12,900 cm−1 (1,315 and 775 nm) is a strong indication for Zn2+ substitution by Cu2+ ions. The result of multiple bands in the symmetric stretching and bending regions confirms the reduction of symmetry from
D
3h
to C
2v
/C
s
for (CO3)2− ion in aurichalcite. The synthetic aurichalcite may be used as a standard for identification of spectral properties of naturally
occurring anhydrous carbonate minerals. 相似文献
9.
A. E. Galashev O. R. Rakhmanova O. A. Novruzova 《Russian Journal of General Chemistry》2009,79(9):1765-1772
Simultaneous interaction of the (H2O)50 cluster with O3 molecules and Cl− ions was studied by the molecular dynamics method. Six O3 molecules located near the cluster were absorbed by the aqueous aggregate, and Cl− ions in turn left the zone of the interaction with the cluster. Some of Cl− ions penetrated inside the formed (O3)6(H2O)50 cluster and come into collision with O3 molecules that split the ozone molecule into atoms. When Cl− ions were removed sufficiently far away from the cluster, the water cluster with absorbed O3 molecules and O atoms was observed for 15.6 ps. The interaction of water molecules with Cl− ions gives rise to an increase in the integral intensity of absorption and emission IR spectra, and also to an essential
decrease in the analogous characteristics of the Raman spectrum in the frequency range of 0 ≤ ω ≤ 1000 cm−1. The presence of Cl− ions did not affect essentially the location of the main band in the IR spectra, but considerably changed the shape of the
bands in the Raman spectrum. 相似文献
10.
Mirjana Mladenović Peter Botschwina Peter Sebald Stuart Carter 《Theoretical chemistry accounts》1998,100(1-4):134-146
The results of various ab initio calculations are reported for the electronic ground state of the acetylide anion. An “Eyring's
lake” in the T-shaped configuration is identified with six different methods (SCF, MP2, CCSD, CCSD-T, CCSD(T), and CEPA–1).
The equilibrium bond lengths of HCC− are estimated to be r
e
(CH)=1.0689(3) ? and R
e
(CC)=1.2464(2) ?, and the ground-state rotational constant is predicted to be B
0=41636(20)MHz. The large permanent dipole moment of μ0=−3.093D should facilitate detection of the anion by microwave spectroscopy. The band centers are predicted to be 3211.3cm−1(ν1), 511.1cm−1(ν2), and 1805.0cm−1(ν3). A large transition dipole moment of 0.477 D is calculated for the ν2 band. Rovibrational levels of HCC− up to approximately 20 000 cm−1 above equilibrium are calculated with DVR-DGB and FBR methods on the basis of a previous CEPA–1 potential energy surface.
Different energy patterns are found and discussed, for which anharmonic and Coriolis resonances are shown to play an important
role.
Received: 27 July 1998 Accepted: 12 August 1998 / Published online: 19 October 1998 相似文献
11.
The packing of [H
2W12O42]10−
polyanions in seven known crystal structures is analyzed. The centers of the polyanions are arranged according to the law
of the F- cell (3 cases) or I- cell (2 cases) or according to a more complex law. “Coherence” in the arrangement of heavy
W atoms belonging to different polyanions is established: there are crystallographic planes with high concentrations of these
atoms;this is an effect of superstructural ordering up to formation of the cation sublattice with light “filler” atoms (K, Mg, Na, N)
partly addressed to the sites of the sublattice.
Translated fromZhumal Strukturnoi Khimii, Vol. 38, No. 4, pp. 732–738, July–August, 1997. 相似文献
12.
A. V. Levanov A. R. Gromov E. E. Antipenko V. V. Lunin 《Russian Chemical Bulletin》2000,49(4):669-673
The yields of hydrogen atoms, oxygen atoms and molecules, and hydroxyl radicals after a microwave discharge in the mixture
of CO2 and H2 were measured by ESR spectroscopy in a flow-type system. A mathematical model of the kinetics of chemical reactions downstream
the microwave discharge was devised. The concentrations of particles that cannot be detected under our experimental conditions
were estimated.
Experimental values of the concentration sensitivity for an RE-1306 ESR spectrometer are as follows: for a pressure of 1 Torr
and optimized detection conditions, H., 1011 cm−3; O., 3·1010 cm−3; OH., 1010 cm−3; O2, 3·1013 cm−3 (Ref. 7); for a pressure of 2 Torr, H., 5·1012 cm−3; O., 2·1012 cm−3; OH., 2.5·1011 cm−3; O2, 7.5·1014 cm−3 8
Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 4, pp. 665–669, April, 2000. 相似文献
13.
Near-infrared (NIR) and IR spectroscopy have been applied for the characterisation of three complex Cu–Zn sulphate/phosphate
minerals, namely ktenasite, orthoserpierite and kipushite. The spectral signatures of the three minerals are quite distinct
in relation to their composition and structure. The effect of structural cation substitution (Zn2+ and Cu2+) on band shifts is significant both in the electronic and in the vibrational spectra of these Cu–Zn minerals. The variable
Cu:Zn ratio between Zn-rich and Cu-rich compositions shows a strong effect on Cu(II) bands in the electronic spectra. The
Cu(II) spectrum is most significant in kipushite (Cu-rich) with bands displayed at high wavenumbers, 11,390 and 7,545 cm−1. The isomorphic substitution of Cu2+ for Zn2+ is reflected in the NIR and IR spectroscopic signatures. The multiple bands for ν3 and ν4 (SO4)2− stretching vibrations in ktenasite and orthoserpierite are attributed to the reduction in symmetry of the sulphate ion from
Td to C2V. The IR spectrum of kipushite is characterised by strong (PO4)3− vibrational modes at 1,090 and 990 cm−1. The range of IR absorption is higher in ktenasite than in kipushite, while it is intermediate in orthoserpierite. 相似文献
14.
V. Yu. Borovkov S. P. Kolesnikov V. I. Koval’chuk J. L. d’Itri 《Russian Chemical Bulletin》2007,56(5):863-869
Adsorption of 13C18O+12C16O mixtures on the Pt(2.9%)/γ-Al2O3, (Pt(2.6%)+Cu(2.7%))/γ-Al2O3, and (Pt(2.6%)+Cu(5.1%))/γ-Al2O3 catalysts was studied by FTIR spectroscopy. On the metallic Pt surface at coverages close to saturation, CO is adsorbed both
strongly and weakly to form linear species for which the vibrational frequencies of the isolated 13C18O molecules adsorbed on Pt are ∼1940 and ∼1970 cm−1, respectively. The redistribution of intensities of the high-and low-frequency absorption bands in the spectra of adsorbed
13C18O indicates that these linear forms are present on the adjacent metal sites. The weak adsorption is responsible for the fast
isotope exchange between the gaseous CO and CO molecules adsorbed on metal. The Pt-Cu alloys, in which the electronic state
of the surface Pt atoms characteristic of monometallic Pt remains unchanged, are formed on the surface of the reduced Pt-Cu
bimetallic catalysts. The decrease in the vibrational frequencies of the isolated C=O bonds in the isolated Pt-CO complexes
suggests that the CO molecules adsorbed on the Cu atoms affect the electronic properties of Pt.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 831–836, May, 2007. 相似文献
15.
16.
H. Rausch 《Journal of Radioanalytical and Nuclear Chemistry》1976,33(2):201-207
Activation analysis and autoradiography were used to investigate the concentration distribution of contaminants in poly-Si−Si3N4−SiO2−Si substrate multilayer structures (SNOS) on sampling each technological product. Samples were irradiated for 36 hrs at a
thermal neutron flux of 4·1013n·cm−2·sec−1. The thin films of the analysed sample were removed stepwise by selective chemical etching using appropriate masking techniques.
Simultaneously autoradiographs were made of the surface of parallel samples activated under the same conditions. The concentration
of the technological contaminants (e.g. Na, Cu, Au) increases in the junction interface of the layers as unambiguously shown
by the results obtained.
Presented at the “4th Symposium on the Recent Developments in Neutron Activation Analysis” Churchill College, Cambridge, 4–7
August, 1975. 相似文献
17.
B. V. Ni 《Journal of Structural Chemistry》1995,36(2):259-264
This paper studies changes in the matrix elements (Ump) of spin-orbit coupling between the nπ*- and ππ*-states, which are induced by the (“chair,” “bath”) distortions of the nuclear configurations of molecules. The analysis is
performed for acridine molecules in which the n-pz atomic orbital (AO) of the heteroatom is directed along the C2 symmetry axis. Earlier, for molecules with a planar nuclear configuration of C2v symmetry and with the heteroatom lying on the C2 axis, we established the dependence of Ump on the symmetry of ππ*-states [Γ(ππ*)=A1 or B2]. The values of Ump differ by more than one order of magnitude; this is in line with the difference between the interconversion rate constants
(Kisc; two or three orders). In this work we have found that this contrast in Ump (and, accordingly, in Kisc) is retained when the nuclear configuration of the acridine molecule is distorted to the “chair” (AC-A) configuration, although
the individuality of both molecular orbital types (nσ-MO and π-MO) and states nπ* and ππ* is annihilated to a certain extent. For the “bath” (AC-B) conformation the difference in Ump considerably diminishes. Reasons for the changes in the matrix elements of spin-orbit coupling and rate constants of the
S-T conversion are analyzed. The available energy level diagram is critically analyzed, and a slightly different diagam as
well as a scheme of nonradiating deactivation of acridine are suggested.
L. Ya. Karpov Physicochemical Scientific Research Institute. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 2, pp. 292–297, March–April, 1995.
Translated by L. Smolina 相似文献
18.
O. Ito 《Research on Chemical Intermediates》1997,23(5):389-402
Efficiencies and rates of electron transfer from various electron donors to excited fullerenes (C60 and C70) have been determined by observing the transient absorption bands in the near-IR region, where the anion radicals of fullerenes
appear. From the rise of the absorption bands of C60
−+ and C70
−+ in the near-IR region, electron transfer takes place via the triplet states (TC60
* and TC70
*) under appropriately low concentrations of electron donors. By analysis of the rise curves C60
−+ and C70
−+, contribution of the excited singlet states (SC60
* and SC70
*) in addition to the route of the triplet states (TC60
* and TC70
*) is confirmed. The quantum yield for electron transfer via the triplet states Φct
T was evaluated by the ratio of [C60
−+]/[TC60
*] (or [C70
−+/[TC70
*]). The Φct
T depends upon the donor-ability, donor concentration, and solvent polarity. The back electron-transfer process, which was
evaluated by observing C60
−+, also depends upon the solvent polarity. 相似文献
19.
A series of ceria-incorporated zirconia (Ce1−xZrxO2,x = 0 to 1) solid solutions were prepared by employing the solution combustion synthesis route. The products were characterized
by XRD and UV-Vis-NIR diffuse reflectance spectroscopy. The materials are crystalline in nature and the lattice parameters
of the solid solution series follow Vegard’s law. Diffuse reflectance spectra of the solid solutions in the UV region show
two intense bands at 250 and 297 nm which are assigned respectively to Ce3+ ← O2−and Ce4+ ← O2− charge transfer transitions. The two vibrational bands in 6960 cm−1 and 5168 cm−1 in the NIR region indicate the presence of surface hydroxyl groups on these materials. 相似文献
20.
The ultraviolet-visible absorption spectrum of C60(OH)18 in water showed an absorption band with λmax = 215 nm and other characteristic absorption bands of C60 are not observed. The singlet-singlet and triplet-triplet absorption bands are not observed in the 400–900 nm region. It
has low reactivity with eaq− and formed an absorption band with λmax = 580 nm. The hydroxyl radicals react with a bimolecular rate constant of 2.4×109 dm3 mol−1 s−1 and showed an absorption band at 540 nm. 相似文献