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1.
So Hee Yoon Jeong Hee Moon Myung Soo Kim 《Journal of the American Society for Mass Spectrometry》2010,21(11):1876-1883
In-source decay (ISD) and post-source decay (PSD) of a peptide ion ([Y6 + H]+) and a preformed ion (benzyltriphenylphosphonium, BTPP) generated by matrix-assisted laser desorption ionization (MALDI)
were investigated with time-of-flight mass spectrometry. α-Cyano-4-hydroxycinammic acid (CHCA) and 2,5-dihydroxybenzoic acid
(DHB) were used as matrices. For both ions, ISD yield was unaffected by delay time, indicating rapid termination of ISD. This
was taken as evidence for rapid expansion cooling of hot “early” plume formed in MALDI. CHCA was hotter than DHB for [Y6 + H]+ while the matrix effect was insignificant for BTPP. The “early” plume temperature estimated utilizing previous kinetic results
was 800–900 K, versus 400–500 K for “late” plume. The results support our previous finding that the temperature of peptide
ions interrogated by tandem mass spectrometry was lower than most rough estimates of MALDI temperature. 相似文献
2.
Mass spectra of the methylated [60]fullerenes were obtained by EI mass spectrometry using “desorption” or “in-beam” technique.
The mass spectra of the methylated fullerenes, C60Men, have the molecular ion peak M+ indicating that the product is stable under the MS (EI) conditions. The appearance of an intense peak at m/z 360 was assigned to the formation of fullerene dication C60++. The remaining peaks were assigned to successive loss of methyl groups from molecular monocation and dication. 相似文献
3.
The “analytical power” of detection systems is investigated, considering typical arrangements in analytical terms. From N
atoms of interest in a sample Z counts are drawn: Z=R N (R registration yield). Crude data ZM contain also background U generated
by interferences: ZM=Z+U. Identification and separation of Z is accompanied by errors ~σMU1/2 due to imperfect distinguishability and to statistical error (σM model inherent factor). With “selectivity”=σM
- (R/Rinterference)1/2 the figure of merit is G=selectivity efficiency/interference)1/2. Sample background dominating, “interference” or both “interference” and “efficiency” have to be cancelled. Present semiconductor
spectrometry of low energy γ-quanta and of large rates is not very far from its limits. Further progress will be obtained
by enhancement of high energy efficiency and reduction of natural background.
相似文献
4.
A. S. Vorob'ev I. I. Furlei A. Sh. Sultanov E. A. Burmistrov 《Russian Chemical Bulletin》1997,46(10):1797-1799
Negative-ion mass spectrometry in the mode of resonance capture of electrons and photoelectron spectroscopy in combination
with quantum-chemical calculations showed that the formation of the resonance states of negative molecular ions in the reaction
of electrons with molecules of the mechanism of intershell Feshbach resonance with the consecutive excitation of an electron
from several higher occupied MO to one vacant MO. In a low-energy region, the resonance at 1.4 eV is a resonance of form and
the resonance at 3–4 eV is the usual electron exciting Feshbach resonance with a parent triplet state (π.π*)3. The one and the same vacant π*CC MO is “active” in all the resonances mentioned.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1892–1894, October, 1997. 相似文献
5.
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
6.
Pridatchenko ML Perlova TY Ben Hamidane H Goloborodko AA Tarasova IA Gorshkov AV Evreinov VV Tsybin YO Gorshkov MV 《Analytical and bioanalytical chemistry》2012,402(8):2521-2529
The amino acid sequence determines the individual protein three-dimensional structure and its functioning in an organism.
Therefore, “reading” a protein sequence and determining its changes due to mutations or post-translational modifications is
one of the objectives of proteomic experiments. The commonly utilized approach is gradient high-performance liquid chromatography
(HPLC) in combination with tandem mass spectrometry. While serving as a way to simplify the protein mixture, the liquid chromatography
may be an additional analytical tool providing complementary information about the protein structure. Previous attempts to
develop “predictive” HPLC for large biomacromolecules were limited by empirically derived equations based purely on the adsorption
mechanisms of the retention and applicable to relatively small polypeptide molecules. A mechanism of the large biomacromolecule
retention in reversed-phase gradient HPLC was described recently in thermodynamics terms by the analytical model of liquid
chromatography at critical conditions (BioLCCC). In this work, we applied the BioLCCC model to predict retention of the intact
proteins as well as their large proteolytic peptides separated under different HPLC conditions. The specific aim of these
proof-of-principle studies was to demonstrate the feasibility of using “predictive” HPLC as a complementary tool to support
the analysis of identified intact proteins in top-down, middle-down, and/or targeted selected reaction monitoring (SRM)-based
proteomic experiments. 相似文献
7.
Attygalle AB Nishshanka U Weisbecker CS 《Journal of the American Society for Mass Spectrometry》2011,22(9):1515-1525
The diagnostic value of the “ortho effect” for unknown identification by mass spectrometry is well known. Here, we report
the existence of a novel “meta effect,” which adds to the repertoire of useful mass spectrometric fragmentation mechanisms.
For example, the meta-specific elimination pathway described in this report enables unequivocal identification of meta isomers
from ortho and para isomers of carboxyanilides. The reaction follows a specific path to eliminate a molecule of meta-benzyne, from the anion produced after the initial decarboxylation of the precursor. Consequently, in the CID spectra of
carboxyanilides, a peak for the (R-CO-NH)– anion is observed only for the meta isomers. For example, the peaks observed at m/z 58, 86, 120, 128, and 170 from acetamido-, butamido-, benzamido, heptamido-, and decanamido-benzoates, respectively, were
specific only to the spectra of meta isomers. 相似文献
8.
Cheng-Kang Chiang Mi-Chen Chiang Zong-Hong Lin Guo-Yu Lan Yang-Wei Lin Huan-Tsung Chang 《Journal of the American Society for Mass Spectrometry》2010,21(7):1204-1207
We have investigated six nanomaterials for their applicability as surfaces for the analyses of peptides and proteins using
surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). Gold nanoparticles (NPs) were useful nanomateriais
for small analytes (e.g., glutathione); Pt nanosponges and Fe3O4 NPs were efficient nanomaterials for proteins, with an upper detectable mass limit of ca. 25 kDa. Nanomateriais have several
advantages over organic matrices, including lower limits of detection for small analytes and lower batch-to-batch variations
(fewer problems associated with “sweet spois”), when used in laser desorption/ionization mass spectrometry. 相似文献
9.
10.
Stefania?Gaudino Chiara?Galas Maria?Belli Sabrina?Barbizzi Paolo?de?Zorzi Radojko?Ja?imovi? Zvonka?Jeran Alessandra?Pati Umberto?Sansone
The measurement of trace-element concentration in soil, sediment and waste, is generally a combination of a digestion procedure
for dissolution of elements and a subsequent measurement of the dissolved elements. “Partial” and “total” digestion methods
can be used in environmental monitoring activities. To compare measurement results obtained by different methods, it is crucial
to determine and to maintain control of the bias of the results obtained by these methods. In this paper, ICP-MS results obtained
after matrix digestion with modified aqua regia (HCl+HNO3+H2O2) method and two “total” digestion methods (microwave aqua regia+HF and HNO3+HF) are compared with those obtained by instrumental neutron activation analysis, a non-destructive analytical method for
the determination of the total mass concentrations of inorganic components in environmental matrices. The comparison was carried
out on eight agricultural soil samples collected in one test area and measured by k0-INAA and ICP-MS to determine As, Co, Cr, Sb and Zn mass concentration. The bias of results for As, Cd, Co, Cr, Cu, Ni, Pb,
Sb and Zn of the three digestion methods were assessed using selected measurement standards. This paper highlights that the
digestion procedure is an integral part of the measurement and can affect the measurement result in environmental analysis. 相似文献
11.
Brent N. Jewett Louis Ramaley Jan C. T. Kwak 《Journal of the American Society for Mass Spectrometry》1999,10(6):529-536
This paper compares two liquid introduction atmospheric pressure ionization techniques for the analysis of alkyl ethoxysulfate (AES) anionic surfactant mixtures by mass spectrometry, i. e., electrospray ionization (ESI) in both positive and negative ion modes and atmospheric pressure chemical ionization (APCI) in positive ion mode, using a triple quadrupole mass spectrometer. Two ions are observed in ESI(+) for each individual AES component, [M + Na]+ and a “desulfated” ion [M − SO3 + H]+, whereas only one ion, [M − Na]− is observed for each AES component in ESI(−). APCI(+) produces a protonated, “desulfated” ion of the form [M − NaSO3 + 2H]+ for each AES species in the mixture under low cone voltage (10 V) conditions. The mass spectral ion intensities of the individual AES components in either the series from ESI(+) or APCI(+) can be used to obtain an estimate of their relative concentrations in the mixture and of the average ethoxylate (EO) number of the sample. The precursor ions produced by either ESI(+) or ESI(−), when subjected to low-energy (50 eV) collision-induced dissociation, do not fragment to give ions that provide much structural information. The protonated, desulfated ions produced by APCI(+) form fragment ions which reveal structural information about the precursor ions, including alkyl chain length and EO number, under similar conditions. APCI(+) is less susceptible to matrix effects for quantitative work than ESI(+). Thus APCI(+) provides an additional tool for the analysis of anionic surfactants such as AES, especially in complex mixtures where tandem mass spectrometry is required for the identification of the individual components. 相似文献
12.
The facilitated transport of penicillin G from aqueous solutions to the stripping phase through bulk liquid membrane (BLM)
containing TBP in 3% iso-octanol and n-butyl acetate was studied. Na2CO3 solution was used as the stripping phase. Experiments were performed as a function of stirring rate, TBP concentration and
type of diluent in the liquid membrane phase, pH, and initial penicillin G concentration in the feed phase, Na2CO3 concentration in the stripping phase, etc. The results showed that the BLM process could carry out the simultaneous separation
and concentration of penicillin G from dilute aqueous solutions, and arise “up-hill” effect due to the characteristic of non-equilibrium
mass transfer. The diffusion of penicillin G complex in the liquid membrane phase played an important role in BLM process.
The mass transfer mechanism of BLM for this system was also discussed. 相似文献
13.
Multivariate analysis of HT/GC-(IT)MS chromatographic profiles of triacylglycerol for classification of olive oil varieties 总被引:1,自引:0,他引:1
Cristina Ruiz-Samblás Luis Cuadros-Rodríguez Antonio González-Casado Francisco de Paula Rodríguez García Paulina de la Mata-Espinosa Juan Manuel Bosque-Sendra 《Analytical and bioanalytical chemistry》2011,399(6):2093-2103
The ability of multivariate analysis methods such as hierarchical cluster analysis, principal component analysis and partial
least squares-discriminant analysis (PLS-DA) to achieve olive oil classification based on the olive fruit varieties from their
triacylglycerols profile, have been investigated. The variations in the raw chromatographic data sets of 56 olive oil samples
were studied by high-temperature gas chromatography with (ion trap) mass spectrometry detection. The olive oil samples were
of four different categories (“extra-virgin olive oil”, “virgin olive oil”, “olive oil” and “olive-pomace” oil), and for the
“extra-virgin” category, six different well-identified olive oil varieties (“hojiblanca”, “manzanilla”, “picual”, “cornicabra”,
“arbequina” and “frantoio”) and some blends of unidentified varieties. Moreover, by pre-processing methods of chemometric
(to linearise the response of the variables) such as peak-shifting, baseline (weighted least squares) and mean centering,
it was possible to improve the model and grouping between different varieties of olive oils. By using the first three principal
components, it was possible to account for 79.50% of the information on the original data. The fitted PLS-DA model succeeded
in classifying the samples. Correct classification rates were assessed by cross-validation. 相似文献
14.
K. E. Collins M. L. M. M. Granja R. G. Pereira Filho T. A. Anazawa I. C. S. F. Jardim 《Chromatographia》1997,45(1):99-103
Summary Poly(methyloctylsiloxane) (PMOS), sorbed into the pores of HPLC silica particles by solvent evaporation, can function as a
useful stationary phase for reversed-phase chromatography. The present work addresses the question of how the PMOS is distributed
in the pores. Measurements of the surface area (BET, N2) of a series of partially loaded samples (0–40% PMOS, m/m) using a typical batch of HPLC silica (10 μm irregular particles
with 6 nm pores) show that the specific surface area of the samples decreases linearly with the specific loading (mass of
PMOS per gram of silica). This result is not consistent with a “film” model in which the PMOS is deposited uniformly on the
pore walls, but is consistent with a model in which long segmented “plugs” of PMOS are deposited within the pore system.
Presented at the 21st ISC held in Stuttgart, Germany, 15th–20th September, 1996 相似文献
15.
Daniel G. Cummings James D. Sommers Mary L. Adamic Marcos Jimenez Jeffrey J. Giglio Kevin P. Carney Karl Grimm 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(3):923-928
A radioactive 137Cs source has been analyzed for the radioactive parent 137Cs and stable decay daughter 137Ba. The ratio of the daughter to parent atoms is used to estimate the date when Cs was purified prior to source encapsulation
(an “age” since purification). The isotopes were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) after chemical
separation. In addition, Ba was analyzed by isotope dilution ICP-MS (ID-ICP-MS). A detailed error analysis of the mass spectrometric
work has been undertaken to identify areas of improvement, as well as quantifying the effect the errors have on the “age”
determined. This paper reports an uncertainty analysis to identifying areas of improvement and alternative techniques that
may reduce the uncertainties. In particular, work on isotope dilution using ICP-MS for the “age” determination of sealed sources
is presented. The results will be compared to the original work done using external standards to calibrate the ICP-MS instrument. 相似文献
16.
V. B. Murachev A. M. Evtushenko A. I. Nesmelov E. A. Ezhova A. V. Orlinkov I. S. Akhrem 《Russian Chemical Bulletin》1997,46(4):714-718
Two criteria for the quantitative estimation of “closeness to the living state” for polymerization systems in which an, important
role belongs to elimination of a proton from the growing carbocation during cationic polymerization are proposed. The first
criterion, (C=C)rel, is the proportion of units with C=C bonds in the polymer chains. The second criterion,k
cl/k
gr, is the ratio of the rate constants for proton elimination and chain growth. The criteria are used in experiments on the
polymerization of isobutene in hexane and dichloromethane induced by complexes of acyl halides with aluminum bromide. Limitations
and fields of application, of these criteria are examined.
For part 6, see Ref. 1
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 745–749, April, 1997. 相似文献
17.
An “average state” of a molecule is defined by distributing the electrons equally among the valence orbitals of a minimal
basis set Hartree-Fock calculation. The resulting eigenvalues, called tempered orbital energies, behave much more like the
Mulliken-Walsh diagram energies or extended Hückel eigenvalues than do the Hartree-Fock canonical orbital energies. 相似文献
18.
The relative cumulative fission yields of 95,97,98,100Mo produced by spontaneous fission of 238U contained in Archaean zircons, were measured by sensitive thermal ionization mass spectrometry (TIMS). The relative yields
for 95,97,98,100Mo are 0.58 : 1.08 : 1.04 : 1.0, respectively. Combined with mass spectrometrically-determined 99,101,102,104Ru fission yields,1 the mass distribution from 95£A£104 can be delineated. Assuming an “absolute” fission yield of 6.1±0.4% for the cumulative fission yield at mass 97, it is
possible to express the Mo and Ru relative spontaneous fission yields for 238U as “absolute” values. There is no evidence for a significant isotope anomaly at mass 98.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
Summary A rapid and simple detection procedure of Aib-containing “peptaibol” polypeptide antibiotics (mycotoxins) in fungal culture
broths is described which employs alkylsilica (Sep-Pak?) cartridges for a selective enrichment, and the utilization of the
unusualα-aminoisobutyric acid (Aib) and amino alcohols as specific marker constituents, which are easily detectable in total hydrolysates.
Preparative isolations from fermentation broths is facilitated by adsorber resin (XAD) column chromatography, and purification
of crude isolates is achieved by silica gel- and sephadex LH-20 chromatography. Preparative HPLC using spherical, totally
porous ODS-bonded phases enables the isolation of uniform peptides, completely free of sequence analogs, from microheterogeneous
peptaibol mixtures, and analytical HPLC of highest resolution allows a “fingerprint” assignment of microheterogeneous peptaibols
of different fungal origin. Fast atom bombardment mass spectrometry is demonstrated to be a rapid and precise method for the
complete sequence determination of peptaibols when employing sophisticated liquid matrix systems including both, lipophilic
tetraethylenglycol and hydrophilic glycerol combined with a selective, trifluoroacetolytic cleavage step carried out directly
“on target” (in situ). The versatility of the methods described is demonstrated with the detection and sequence determination of the new membrane-altering
eicosapeptide named gliodeliquescin A from the soil fungusGliocladium deliquescens NRRL 3091 establishing the occurence of peptaibols in that fungal genus for the first time.
Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984 相似文献
20.
Influence of “direct” and “indirect” pathways of dissociative chemisorption on the form of kinetic dependences ϕ(MCS) and
S(ϕ) was studied by the Monte Carlo method. Langmuir adsorption observed at Sindir/Sdir≤0.1 gradually changes to island-mediated adsorption with an increase of the “indirect” adsorption contribution at 0.1≤Sindir/Sdir≤1.0. At Sindir/Sdir≥1.0 the island-mediated adsorption dominates: large adsorption islands arise and gradually grow. 相似文献