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Junhua Wei Ji Chen Jack Martin Miller 《Rapid communications in mass spectrometry : RCM》2001,15(3):169-181
A detailed study of the solution chemistry and mass spectrometry of six carboxylato-organogermanium compounds in aqueous solution has been carried out using electrospray ionization and MSn techniques. The different types of hydrolysis products and their probable structures, which include the oligomers and their fragment ions plus water adduct ions formed by ion-molecule reactions, are presented, e.g., HO-cyclic-(-Ge(O−)CH2CH2COO) A, HO-cyclic-(-Ge(O-cyclic-(Ge(O−)CH2CH2COO)CH2CH2COO) B, −OGeO-cyclic-(-Ge(OH)CH2CH2COO) C, and −CH=CHGeO-cyclic-(-Ge(OH)CH2CH2COO) D, etc. The proposed cyclic structures are confirmed by theoretical calculations. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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Lysoglycerophosphocholine lipids (lyso-GPC) are important intermediates in the synthesis and metabolism of glycerophosphocholine lipids which are major components of the cellular lipid bilayer. Significant differences in the collisional induced decomposition (CID) behavior were observed for each of the four different subtypes of lyso-GPC in both positive and negative ions. A major difference was observed in the initial CID product ions derived from lyso-GPC [M + H]+ with the loss of water that was very abundant for acyl lyso-GPC which have a fatty acid ester substituent at either the sn-1 or sn-2 positions. Loss of neutral water was not very prominent in the case of plasmenyl and plasmanyl lyso-GPC species. The mechanism responsible for this difference in behavior of lyso-GPC subtypes was consistent with a higher proton affinity of carboxyl carbonyl oxygen atoms and vinyl ether oxygen atoms found in acyl and plasmenyl lyso-GPC lipids, respectively, as compared to the carbinol oxygen atom common to all lyso-GPC species. Collisional activation of lyso-GPC negative ions [M - 15]- also revealed distinctive differences in product ions derived from acyl and ether lyso-GPC species. The acyl compounds showed the facile elimination of a highly stable carboxylate anion, whereas plasmenyl species underwent fragmentation with loss of a neutral aldehyde, likely a result of rearrangement involving the double bond in the vinyl ether moiety. The alkyl ether species (plasmanyl lyso-GPC lipids) did not undergo either decomposition reaction observed for the other lyso-GPC subtypes which permitted differentiation of acyl, plasmenyl, and plasmanyl lyso-GPC subtypes. 相似文献
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Electrospray ionization mass spectrometry of ginsenosides 总被引:1,自引:0,他引:1
Ginsenosides R(b1), R(b2), R(c), R(d), R(e), R(f), R(g1), R(g2) and F(11) were studied systematically by electrospray ionization mass spectrometry in positive- and negative-ion modes with a mobile-phase additive, ammonium acetate. In general, ion sensitivities for the ginsenosides were greater in the negative-ion mode, but more structural information on the ginsenosides was obtained in the positive-ion mode. [M + H](+), [M + NH(4)](+), [M + Na](+) and [M + K](+) ions were observed for all of the ginsenosides studied, with the exception of R(f) and F(11), for which [M + NH(4)](+) ions were not observed. The signal intensities of [M + H](+), [M + NH(4)](+), [M + Na](+) and [M + K](+) ions varied with the cone voltage. The highest signal intensities for [M + H](+) and [M + NH(4)](+) ions were obtained at low cone voltage (15-30 V), whereas those for [M + Na](+) and [M + K](+) ions were obtained at relatively high cone voltage (70-90 V). Collision-induced dissociation yielded characteristic positively charged fragment ions at m/z 407, 425 and 443 for (20S)-protopanaxadiol, m/z 405, 423 and 441 for (20S)-protopanaxatriol and m/z 421, 439, 457 and 475 for (24R)-pseudoginsenoside F(11). Ginsenoside types were identified by these characteristic ions and the charged saccharide groups. Glycosidic bond cleavage and elimination of H(2)O were the two major fragmentation pathways observed in the product ion mass spectra of [M + H](+) and [M + NH(4)](+). In the product ion mass spectra of [M - H](-), the major fragmentation route observed was glycosidic bond cleavage. Adduct ions [M + 2AcO + Na](-), [M + AcO](-), [M - CH(2)O + AcO](-), [M + 2AcO](2-), [M - H + AcO](2-) and [M - 2H](2-) were observed at low cone voltage (15-30 V) only. 相似文献
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Huikko K Kotiaho T Yli-Kauhaluoma J Kostiainen R 《Journal of mass spectrometry : JMS》2002,37(2):197-208
The bisphosphonate family with a P-C-P structure is a broad class of drugs, widely investigated as potential inhibitors in bone diseases and calcium metabolic disorders. In this study, the mass spectrometric (MS) behavior and fragmentation of clodronate and related bisphosphonate and phosphonate compounds was studied by using negative ion electrospray ionization (ESI) with triple quadrupole and ion trap instruments. The effect of pH on the degree of deprotonation of the polyprotic bisphosphonic and phosphonic acids in negative ion ESI-MS was investigated, and the degree of deprotonation in the ESI mass spectra and the dissociation in the liquid phase were compared. The results provide evidence that the measured ESI mass spectra do not correlate with the chemistry in the liquid phase owing to the decrease in the pH of the solvent droplets during the ion evaporation process and the charge state neutralization in the gas phase. Ion trap MS(n) provided useful information on the fragmentation study of clodronate and related bisphosphonate and phosphonate compounds, in which interesting fragmentation pathways including the direct elimination of carbon monoxide from deprotonated bisphosphonates and formation of a P-P bond were observed. Reactions between the product ions with a -PO(2) group and residual water in the ion trap or in the high-pressure region of the triple quadrupole instrument formed other unexpected fragmentation paths for all the bisphosphonates studied. 相似文献
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Sawaya AC Tomazela DM Cunha IB Bankova VS Marcucci MC Custodio AR Eberlin MN 《The Analyst》2004,129(8):739-744
Crude ethanolic extracts of propolis, a natural resin, have been directly analysed using electrospray ionization mass (ESI-MS) and tandem mass spectrometry (ESI-MS/MS) in the negative ion mode. European, North American and African samples have been analyzed, but emphasis has been given to Brazilian propolis which displays diverse and region-dependent chemical composition. ESI-MS provides characteristic fingerprint mass spectra, with propolis samples being divided into well-defined groups directly related to their geographical origins. Chemometric multivariate analysis statistically demonstrates the reliability of the ESI-MS fingerprinting method for propolis. On-line ESI-MS/MS tandem mass spectrometry of characteristic [M - H](-) ion markers provides an additional dimension of fingerprinting selectivity, while structurally characterizing the ESI-MS marker components of propolis. By comparison with standards, eight such markers have been identified: para-coumaric acid, 3-methoxy-4-hydroxycinnamaldehyde, 2,2-dimethyl-6-carboxyethenyl-2H-1-benzopyran, 3-prenyl-4-hydroxycinnamic acid, chrysin, pinocembrin, 3,5-diprenyl-4-hydroxycinnamic acid and dicaffeoylquinic acid. The negative mode ESI-MS fingerprinting method is capable of discerning distinct composition patterns to typify, to screen the sample origin and to reveal characteristic details of the more polar and acidic chemical components of propolis samples from different regions of the world. 相似文献
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Araújo AS da Rocha LL Tomazela DM Sawaya AC Almeida RR Catharino RR Eberlin MN 《The Analyst》2005,130(6):884-889
After just simple degassing, dilution, pH adjustment and direct flow injection, characteristic fingerprint spectra of beer samples have been obtained by fast (few seconds) electrospray ionization mass spectrometry (ESI-MS) analysis in both the negative and positive ion modes. A total of 29 samples belonging to the two main beer types (lagers and ales) and several beer subtypes from USA, Europe and Brazil could be clearly divided into three groups both by simple visual inspection of their ESI(+)-MS and ESI(-)-MS fingerprints as well as by chemometric treatment of the MS data. Diagnostic ions with contrasting relative abundances in both the positive and negative ion modes allow classification of beers into three major types: P = pale (light) colored (pilsener, pale ale), D = dark colored (bock, stout, porter, mild ale) and M = malt beer. For M beers, samples of a dark and artificially sweetened caramel beer produced in Brazil and known as Malzbiers were used. ESI-MS/MS on these diagnostic beer cations and anions, most of which are characterized as arising from ionization of simple sugars, oligosaccharides, and iso-alpha-acids, yield characteristic tandem mass spectra adding a second and optional MS dimension for improved selectivity for beer characterization by fingerprinting. Direct ESI-MS or ESI-MS/MS analysis can therefore provide fast and reliable fingerprinting characterization of beers, distinguishing between types with different chemical compositions. Other unusual polar components, impurities or additives, as well as fermentation defects or degradation products, could eventually be detected, making the technique promising for beer quality control. 相似文献
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Zheng Yang Taichang Zhang Yang Pan Xin Hong Zichao Tang Fei Qi 《Journal of the American Society for Mass Spectrometry》2009,20(3):430-434
For the comprehensive analysis of organic compounds, especially thermal labile and nonpolar compounds, an electrospray/vacuum
ultraviolet (VUV) single-photon ionization (ES-SPI) method was developed. The fine droplets of the sample solution from the
electrospray process were directed through a quartz capillary and two skimmers to form a molecular beam into a high vacuum
ionization chamber. The neutral sample molecules were softly ionized with tunable VUV light and analyzed with a reflection
time-of-flight mass spectrometer (RTOF-MS). The ionization energy (IE) and appearance onsets of fragments were obtained based
on the photoionization efficiency (PIE) spectrum. The isomers can also be distinguished. With this new method, clean (fragment-free)
mass spectra of nonpolar compounds, such as benzene, cyclohexane, and some thermal labile solid compounds (triphenylamine,
thioacetamide, and urea) have been obtained without any tedious pretreatment. The components of complex mixtures (gasoline
and kerosene) can be identified. Furthermore, quantitative analysis of the components can be obtained based on photoionization
cross section data. This method may be used for quantitative analysis of small biomolecules and natural products. 相似文献
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Frańska M 《European journal of mass spectrometry (Chichester, England)》2005,11(1):103-106
Nucleobases and alkali metal cations, under electrospray ionisation conditions, tend to form the so-called magic number clusters (unusually stable clusters in comparison with the neighbouring ones). The effect of the ion source parameters, namely cone voltage and desolvation temperature and relative concentrations of thymine and RbCl on the [T5+Rb]+ ion abundance has been studied. 相似文献
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Klaus Eckart Joachim Spiess 《Journal of the American Society for Mass Spectrometry》1995,6(10):912-919
Stepwise binding of biotin to streptavidin via several intermediates was monitored with electrospray ionization mass spectrometry (ESIMS). Protein ligand interactions that result in conformational changes could be recognized with ESIMS by a mass shift and a change of the average multiple charge state of this protein. In addition, mass spectrometry for the ions in the gas phase revealed a much greater strength of the noncovalent bonds between the streptavidin subunits in the tetrameric complex than between the streptavidin and biotin molecules and remarkable differences in stability for the different charge states of the biotin-streptavidin noncovalent complex. 相似文献
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Zemski Berry KA Murphy RC 《Journal of the American Society for Mass Spectrometry》2004,15(10):1499-1508
Collision-induced dissociation (CID) of the [M + H]+ of glycerophospholipids typically results in abundant fragment ions that are related to the polar head group or loss of the
polar head group. An exception to this general rule occurs for glycerophosphoethanolamines (GPEtn), which are a class of phospholipids
that can have an acyl, 1-O-alkyl, or 1-O-alk-1′-enyl group as a substituent at the sn-1 position. The CID of the [M + H]+ of diacyl-GPEtn typically results in the expected loss of the phosphoethanolamine head group (141 Da). Therefore, constant
neutral loss of 141 Da has been used as a diagnostic tool for the determination of GPEtn species in complex lipid mixtures.
One disadvantage in using constant neutral loss of 141 Da in order to determine GPEtn content in lipid mixtures is that plasmalogen
GPEtn does not undergo neutral loss of phosphoethanolamine to the same extent as diacyl-GPEtn. The current studies have used
positive ion mode electrospray tandem mass spectrometry to study the collision-induced dissociation of various GPEtn plasmalogens
present in the phospholipid membranes of human neutrophils. The CID of the [M + H]+ of plasmalogen GPEtn resulted in two prominent fragment ions; one that was characteristic of the sn-1 position and one that was characteristic of the sn-2 position. These two ions were used to detect specific molecular species of GPEtn containing esterified arachidonate (precursors
of m/z 361) present in the human neutrophil. 相似文献
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Fifteen identified C-18 fatty acyl-containing saponin structures from Quillaja saponaria Molina have been investigated by electrospray ionization ion-trap multiple-stage mass spectrometry (ESI-IT-MS(n)) in positive ion mode. Their MS(1)-MS(3) spectra were analyzed and ions corresponding to useful fragments, important for the structural identification of Quillaja saponins, were recognized. A few key fragments could describe the structural variations in the C-3 and the C-28 oligosaccharides of the Quillaja saponins. A flowchart involving a stepwise procedure based on key fragments from the MS(1)-MS(3) spectra of these saponins, together with key fragments from these saponins and 13 previously investigated saponins, was constructed for the identification of structural elements in Quillaja saponins. Peak intensity ratios in MS(3) spectra were found to be correlated to structural features of the investigated saponins and is therefore of value for the identification of regioisomers. 相似文献
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AZT H-phosphonates conjugated with steroids were synthesized and determined by positive and negative ion electrospray ionization mass spectrometry (ESI-MS) in conjunction with tandem mass spectrometry (MS/MS). The fragmentation pathways were investigated in detail. There are very different characteristic fragment ions in the positive and negative ion MS/MS spectra. The azide group of compounds 6a and 6b underwent either elimination of HN(3) or rearrangement to an amine in both positive and negative ion mass spectrometry. 相似文献
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Electrospray ionization tandem mass spectrometry analysis of isopimarane diterpenes from Velloziaceae
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Angelo da Cunha Pinto Ricardo Vessecchi Carmelita Gomes da Silva Ana Carolina Lourenço Amorim Helvécio Martins dos Santos Júnior Michelle Jakeline Cunha Rezende Paul J. Gates Claudia Moraes Rezende Norberto Peporine Lopes 《Rapid communications in mass spectrometry : RCM》2016,30(1):61-68