Secondary ion mass spectrometry (SIMS) has inherent features of high sensitivity, great dynamic range, and capability to provide spatially resolved chemical information making it well suited for trace and microanalysis of diverse materials. The various SIMS methods used to derive the boron distribution in hepatoma cells, to investigate the intcr-iayer reactions in multi-layer ceramic structural materials, and to evaluate the effects of fabrication on microstructural and functional properties in semiconductor devices, are presented to illustrate possible roles of SIMS in microanalysis. 相似文献
The new algorithm calculated mass and abundance for polyisotopic ion by low‐resolution mass spectrometry was developed based on probability theory. The results of mass and abundance data of polyisotopic ion calculated by the algorithm were coincided with the experimental values. By comparison with the Kubinyi's method, our algorithm is simpler and easier to master for operator. 相似文献
Over the last two decades, native mass spectrometry (MS) has emerged as a valuable tool to study intact proteins and noncovalent protein complexes. Studied experimental systems range from small-molecule (drug)–protein interactions, to nanomachineries such as the proteasome and ribosome, to even virus assembly. In native MS, ions attain high m/z values, requiring special mass analyzers for their detection. Depending on the particular mass analyzer used, instrumental mass resolution does often decrease at higher m/z but can still be above a couple of thousand at m/z 5000. However, the mass resolving power obtained on charge states of protein complexes in this m/z region is experimentally found to remain well below the inherent instrument resolution of the mass analyzers employed. Here, we inquire into reasons for this discrepancy and ask how native MS would benefit from higher instrumental mass resolution. To answer this question, we discuss advantages and shortcomings of mass analyzers used to study intact biomolecules and biomolecular complexes in their native state, and we review which other factors determine mass resolving power in native MS analyses. Recent examples from the literature are given to illustrate the current status and limitations.
Paclitaxel (PTX) is a popular anticancer drug used in the treatment of various types of cancers. PTX is metabolized in the human liver by cytochrome P450 to two structural isomers, 3′-p-hydroxypaclitaxel (3p-OHP) and 6α-hydroxypaclitaxel (6α-OHP). Analyzing PTX and its two metabolites, 3p-OHP and 6α-OHP, is crucial for understanding general pharmacokinetics, drug activity, and drug resistance. In this study, electrospray ionization ion mobility mass spectrometry (ESI-IM-MS) and collision induced dissociation (CID) are utilized for the identification and characterization of PTX and its metabolites. Ion mobility distributions of 3p-OHP and 6α-OHP indicate that hydroxylation of PTX at different sites yields distinct gas phase structures. Addition of monovalent alkali metal and silver metal cations enhances the distinct dissociation patterns of these structural isomers. The differences observed in the CID patterns of metalated PTX and its two metabolites are investigated further by evaluating their gas-phase structures. Density functional theory calculations suggest that the observed structural changes and dissociation pathways are the result of the interactions between the metal cation and the hydroxyl substituents in PTX metabolites.
Electrochemically assisted oxidation off-line combined with UPLC/ESI–MS and ion mobility mass spectrometry enabled us to gain insight into the oxidation mechanisms of xanthohumol. Several types of monomeric oxidation products were identified, i.e., monohydroxylated and dehydrogenated derivatives and related quinones. Besides, high contents of dimers were observed. The structures of four main oxidative condensation products of two xanthohumol molecules were proposed based on combination of retention time, exact mass measurement, fragmentation pattern, data from on-line ion mobility mass spectrometric experiments and with the support of independent electrochemical experiments. To the best of our knowledge, this is the first evidence on formation of xanthohumol dimers. The effect of the pH on the generation of oxidation products was further investigated. The monomeric and dimeric oxidation products are favored at pH of 5.5 and 4.5, respectively.
Results from static SIMS analysis of six thermoplastic polymers — polytetrafluoroethylene (PTFE), polyethylene (PE), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polystyrene (PS) and polycarbonate (PC) — using a magnetic-sector SIMS instrument and O2+ primary beam are presented. For PTFE as a representative sample, the charging effect is reduced only with a metal grid when analyzing positive secondary ions. When negative secondary ions are analyzed, excessive charges are self-compensated with a normal-incidence electron gun. Positive-ion spectra collected agree with spectra obtained using either a quadrupole or time-of-flight SIMS instrument and noble-gas ion beams. The agreement is objectively demonstrated by means of the capability to compare spectra in the NIST/EPA/MSDC mass spectral database. The merits of the use of high-mass resolution, of which magnetic-sector SIMS is inherently capable, to provide analytical information about the molecular species native to the sample are demonstrated in distinguishing three ambiguous peaks with nominal mass ratios m/z = 27, 39 and 59 from PMMA. 相似文献
A study is presented of the effects of sample temperature on the sputter depth profiling of two organic materials, NPB (N,N′-Di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine) and Irganox 1010, using a 5 keV Ar2000+ cluster ion beam and analysis by secondary ion mass spectrometry. It is shown that at low temperatures, the yields increase slowly with temperature in accordance with the Universal Sputtering Yield equation where the energy term is now modified by Trouton’s rule. This occurs up to a transition temperature, TT, which is, in turn, approximately 0.8TM, where TM is the sample melting temperature in Kelvin. For NPB and Irganox 1010, these transition temperatures are close to 15 °C and 0 °C, respectively. Above this temperature, the rate of increase of the sputtering yield rises by an order of magnitude. During sputtering, the depth resolution also changes with temperature with a very small change occurring below TT. At higher temperatures, the depth resolution improves but then rapidly degrades, possibly as a result first of local crater surface diffusion and then of bulk inter-diffusion. The secondary ion spectra also change with temperature with the intensities of the molecular entities increasing least. This agrees with a model in which the molecular entities arise near the crater rim. It is recommended that for consistent results, measurements for organic materials are always made at temperatures significantly below TT or 0.8 TM, and this is generally below room temperature.
The chemical components analysis of single cell is important for the understanding of physiological processes such as cell growth, signal transduction and apoptosis. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a sensitive surface analysis technique with high spatial resolution, which has been used for single cell and micro-area analysis. However, relatively low ionization yield of biomolecules limited its wide applications in single cell analysis. Herein, we used metal substrate and matrix material to enhance the ionization yield of lipids. The signal intensity of phosphatidylcholine (PC 40:0) casted on the matrix/gold-coated silicon substrate was 65 times higher than that on the silicon wafer. The signal enhancement of phosphatidylcholine (PC 34:1) on single cell surface cultured on matrix/gold-coated silicon substrate was observed as well. Owing to the influence of irregular topography and complex chemical environment of cell, the increase of lipids signal was smaller. Delayed extraction mode of ToF-SIMS overcame the effects of cell topography, leading to further enhancement of the signal intensity of lipids. Meanwhile, simultaneous high spatial resolution of chemical imaging and high mass resolution of the mass spectra of single cells were obtained. Our strategies provided new insights into the study of cell metabolism and cell-environment interactions. 相似文献
