当前期刊: Journal of Mass Spectrometry Go to current issue    加入关注   
显示样式:        排序: 导出
我的关注
我的收藏
您暂时未登录!
登录
  • High‐resolution ion mobility spectrometry‐mass spectrometry of isomeric/isobaric ribonucleotide variants
    J. Mass Spectrom. (IF 2.267) Pub Date : 2020-01-19
    Thomas Kenderdine; Reza Nemati; Andrew Baker; Martin Palmer; Jakub Ujma; Molly FitzGibbon; Limin Deng; Maksim Royzen; James Langridge; Daniele Fabris

    In this report, we explored the benefits of cyclic ion mobility (cIM) mass spectrometry in the analysis of isomeric post‐transcriptional modifications of RNA. Standard methyl‐cytidine samples were initially utilized to test the ability to correctly distinguish different structures sharing the same elemental composition and thus molecular mass. Analyzed individually, the analytes displayed characteristic arrival times (tD) determined by the different positions of the modifying methyl groups onto the common cytidine scaffold. Analyzed in mixture, the widths of the respective signals resulted in significant overlap that initially prevented their resolution on the tD scale. The separation of the four isomers was achieved by increasing the number of passes through the cIM device, which enabled to fully differentiate the characteristic ion mobility behaviors associated with very subtle structural variations. The placement of the cIM device between the mass‐selective quadrupole and the time‐of‐flight analyzer allowed us to perform gas‐phase activation of each of these ion populations, which had been first isolated according to a common mass‐to‐charge ratio and then separated on the basis of different ion mobility behaviors. The observed fragmentation patterns confirmed the structures of the various isomers thus substantiating the benefits of complementing unique tD information with specific fragmentation data to reach more stringent analyte identification. These capabilities were further tested by analyzing natural mono‐nucleotide mixtures obtained by exonuclease digestion of total RNA extracts. In particular, the combination of cIM separation and post‐mobility dissociation allowed us to establish the composition of methyl‐cytidine and methyl‐adenine components present in the entire transcriptome of HeLa cells. For this reason, we expect that this technique will benefit not only epitranscriptomic studies requiring the determination of identity and expression levels of RNA modifications, but also metabolomics investigations involving the analysis of natural extracts that may possibly contain subsets of isomeric/isobaric species.

    更新日期:2020-01-21
  • Developing Front‐end Devices for Improved Sample Preparation in MS‐based Proteome Analysis
    J. Mass Spectrom. (IF 2.267) Pub Date : 2020-01-20
    Alan A. Doucette; Jessica L. Nickerson

    Chemical analysis has long relied on instrumentation, from the simplest (eg burets) to the more sophisticated (eg mass spectrometers) to facilitate precision measurements. Regardless of their complexity, the development of a new instrumental device can be a valued approach to address problems in science. In this perspective, we outline the process of novel device design, from early phase conception to the manufacturing and testing of the tool or gadget. Focus is placed on the development of improved front‐end devices to facilitate protein sample manipulations ahead of mass spectrometry, which therefore augment the proteomics workflow.. Highlighted are some of the many training secrets, choices and challenges that are inherent to the often iterative process of device design. In hopes of inspiring others to pursue instrument design to address relevant research questions, we present a summary list of points to consider prior to innovating their own devices.

    更新日期:2020-01-21
  • A GENERAL APPROACH TO CALCULATING ISOTOPIC DISTRIBUTIONS FOR MASS SPECTROMETRY
    J. Mass Spectrom. (IF 2.267) Pub Date : 2020-01-19
    J.A.M.E.S.A. Yergey

    Fundamental principles for obtaining mass spectral isotopic distributions are applied to a general computer program which can be used to calculate and present in tabular and graphic form the isotopic contributions for any molecular formula. A unique feature is the retention of the isotopic distribution, exact mass, and absolute abundance for all individual peaks at each mass. Special considerations have been made for the large number of isotopic combinations which occur for many higher mass compounds. The computer program accepts the input of a molecular formula followed by interactive input of a number of parameters which affect the final presentation of the theoretical distribution profile.

    更新日期:2020-01-21
  • Characterization of volatile metabolites formed by molds on barley by mass and ion mobility spectrometry
    J. Mass Spectrom. (IF 2.267) Pub Date : 2020-01-16
    A. Erler; D. Riebe; T. Beitz; H.‐G. Löhmannsröben; D. Grothusheitkamp; T. Kunz; F.‐J. Methner

    The contamination of barley by molds on the field or in storage leads to the spoilage of grain and the production of mycotoxins which causes major economic losses in malting facilities and breweries. Therefore, on‐site detection of hidden fungus contaminations in grain storages based on the detection of volatile marker compounds is of high interest. In this work, the volatile metabolites of ten different fungus species are identified by gas chromatography (GC) combined with two complementary mass spectrometric methods, namely electron impact‐ (EI) and chemical ionization at atmospheric pressure (APCI) mass spectrometry (MS). The APCI source utilizes soft X‐radiation which enables the selective protonation of the volatile metabolites largely without side‐reactions. Nearly 80 volatile or semivolatile compounds from different substance classes, namely alcohols, aldehydes, ketones, carboxylic acids, esters, substituted aromatic compounds, alkenes, terpenes, oxidized terpenes, sesquiterpenes and oxidized sesquiterpenes, could be identified. The profiles of volatile and semivolatile metabolites of the different fungus species are characteristic of them and allow their safe differentiation. The application of the same GC parameters and APCI source allows a simple method transfer from MS to ion mobility spectrometry (IMS) which permits on‐site analyses of grain stores. Characterization of IMS yields limits of detection very similar to those of APCI‐MS. Accordingly, more than 90 % of the volatile metabolites found by APCI‐MS were also detected in IMS. In addition to different fungus genera, different species of one fungus genus could also be differentiated by GC‐IMS.

    更新日期:2020-01-17
  • Cover Picture
    J. Mass Spectrom. (IF 2.267) Pub Date : 2020-01-17
    更新日期:2020-01-17
  • Mass spectrometry and planetary exploration: A brief review and future projection
    J. Mass Spectrom. (IF 2.267) Pub Date : 2020-01-17
    Ricardo Arevalo; Ziqin Ni; Ryan M. Danell
    更新日期:2020-01-17
  • Investigating the interactions of the first 17 amino acid residues of Huntingtin with lipid vesicles using mass spectrometry and molecular dynamics
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-16
    Ahmad Kiani Karanji; Maryssa Beasley; Daud Sharif; Ali Ranjbaran; Justin Legleiter; Stephen J. Valentine

    The first 17 amino acid residues of Huntingtin protein (Nt17 of htt) are thought to play an important role in the protein's function; Nt17 is one of two membrane binding domains in htt. In this study the binding ability of Nt17 peptide with vesicles comprised of two subclasses of phospholipids is studied using electrospray ionization ‐ mass spectrometry (ESI‐MS) and molecular dynamics (MD) simulations. Overall, the peptide is shown to have a greater propensity to interact with vesicles of phosphatidylcholine (PC) rather than phosphatidylethanolamine (PE) lipids. Mass spectra show an increase in lipid‐bound peptide adducts where the ordering of the number of such specie is 1,2‐dioleoyl‐sn‐glycero‐3‐phosphocholine (DOPC) > 1‐palmitoyl‐2‐oleoyl‐glycero‐3‐phosphocholine (POPC) > 1‐palmitoyl‐2‐oleoyl‐sn‐glycero‐3 phosphoethanolamine (POPE). MD simulations suggest that the compactness of the bilayer plays a role in governing peptide interactions. The peptide shows greater disruption of the DOPC bilayer order at the surface and interacts with the hydrophobic tails of lipid molecules via hydrophobic residues. Conversely, the POPE vesicle remains ordered and lipids display transient interactions with the peptide through the formation of hydrogen bonds with hydrophilic residues. The POPC system displays intermediate behavior with regard to the degree of peptide‐membrane interaction. Finally, the simulations suggest a helix stabilizing effect resulting from the interactions between hydrophobic residues and the lipid tails of the DOPC bilayer.

    更新日期:2020-01-14
  • Analysis of the chemical components of Qixianqingming granules and their metabolites in rats by UPLC‐ESI‐Q‐TOF‐MS
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-11
    Bei Zhang; Mo Ying Li; Xu Ming Luo; Xiong Biao Wang; Tong Wu

    Qixianqingming granules (QXQM) comprise a traditional Chinese medicine (TCM) formula that was developed based on the combination of TCM theory and clinical practice. This formula has been proven to effectively treat asthma. In this study, an analytical procedure using ultraperformance liquid chromatography, coupled with electrospray ionization quadrupole time‐of‐flight mass spectrometry, was established for the rapid separation and sensitive identification of the chemical components in QXQM and its metabolites in serum of rats. Seventy‐two compounds were systematically identified in QXQM, including flavonoids, terpenoids, anthraquinones, phenylethanoid glycosides, stilbenes, alkaloids, and organic acids. Thirteen prototype compounds and 29 metabolites were detected in the serum of rats. The results provided fundamental information for further studying the mechanisms and clinical application of QXQM.

    更新日期:2020-01-14
  • A biuret‐derived, MS‐cleavable cross‐linking reagent for protein structural analysis: A proof‐of‐principle study
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-09
    Christoph Hage; Claudio Iacobucci; Michael Götze; Andrea Sinz

    Chemical cross‐linking combined with mass spectrometry (XL‐MS) and computational modeling has evolved as an alternative method to derive protein 3D structures and to map protein interaction networks. Special focus has been laid recently on the development and application of cross‐linkers that are cleavable by collisional activation as they yield distinct signatures in tandem mass spectra. Building on our experiences with cross‐linkers containing an MS‐labile urea group, we now present the biuret‐based, CID‐MS/MS‐cleavable cross‐linker imidodicarbonyl diimidazole (IDDI) and demonstrate its applicability for protein cross‐linking studies based on the four model peptides angiotensin II, MRFA, substance P, and thymopentin.

    更新日期:2020-01-14
  • Study of the noncovalent interactions of ginsenosides and amyloid‐β‐peptide by CSI‐MS and molecular docking
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-28
    Yanan Zhou; Su Chen; Jinping Qiao; Yanyun Cui; Chang Yuan; Lan He; Jin Ouyang

    Noncovalent interactions between drugs and proteins play significant roles for drug metabolisms and drug discoveries. Mass spectrometry has been a commonly used method for studying noncovalent interactions. However, the harsh ionization process in electrospray ionization mass spectrometry (ESI‐MS) is not conducive to the preservation of noncovalent and unstable biomolecular complexes compared with the cold spray ionization mass spectrometry (CSI‐MS). A cold spray ionization providing a stable solvation‐ionization at low temperature is milder than ESI, which was more suitable for studying noncovalent drug‐protein complexes with exact stoichiometries. In this paper, we apply CSI‐MS to explore the interactions of ginsenosides toward amyloid‐β‐peptide (Aβ) and clarify the therapeutic effect of ginsenosides on Alzheimer's disease (AD) at the molecular level for the first time. The interactions of ginsenosides with Aβ were performed by CSI‐MS and ESI‐MS, respectively. The ginsenosides Rg1 bounded to Aβ at the stoichiometries of 1:1 to 5:1 could be characterized by CSI‐MS, while dehydration products are more readily available by ESI‐MS. The binding force depends on the number of glycosyls and the type of ginsenosides. The relative binding affinities were sorted in order as follows: Rg1 ≈ Re > Rd ≈ Rg2 > Rh2, protopanaxatriol by competition experiments, which were supported by molecular docking experiment. CSI‐MS is expected to be a more appropriate approach to determine the weak but specific interactions of proteins with other natural products especially polyhydroxy compounds.

    更新日期:2020-01-14
  • Rapid and sensitive identification of ricin in environmental samples based on lactamyl agarose beads using LC‐MS/MS (MRM)
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-09
    Liron Feldberg; Ofir Schuster; Eytan Elhanany; Orly Laskar; Shmuel Yitzhaki; Sigalit Gura

    Ricin, a plant‐derived toxin extracted from the seeds of Ricinus communis (castor bean plant), is one of the most toxic proteins known. Ricin's high toxicity, widespread availability, and ease of its extraction make it a potential agent for bioterrorist attacks. Most ricin detection methods are based on immunoassays. These methods may suffer from low efficiency in matrices containing interfering substances, or from false positive results due to antibody cross reactivity, with highly homologous proteins. In this study, we have developed a simple, rapid, sensitive, and selective mass spectrometry assay, for the identification of ricin in complex environmental samples. This assay involves three main stages: (a) Ricin affinity capture by commercial lactamyl‐agarose (LA) beads. (b) Tryptic digestion. (c) LC‐MS/MS (MRM) analysis of tryptic fragments. The assay was validated using 60 diverse environmental samples such as soil, asphalt, and vegetation, taken from various geographic regions. The assay's selectivity was established in the presence of high concentrations of competing lectin interferences. Based on our findings, we have defined strict criteria for unambiguous identification of ricin. Our novel method, which combines affinity capture beads followed by MRM‐based analysis, enabled the identification of 1 ppb ricin spiked into complex environmental matrices. This methodology has the potential to be extended for the identification of ricin in body fluids from individuals exposed (deliberately or accidentally) to the toxin, contaminated food or for the detection of the entire family of RIP‐II toxins, by applying multiplex format.

    更新日期:2020-01-14
  • Feature selection for OPLS discriminant analysis of cancer tissue lipidomics data
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-09
    Alisa O. Tokareva; Vitaliy V. Chagovets; Natalia L. Starodubtseva; Niso M. Nazarova; Maria E. Nekrasova; Alexey S. Kononikhin; Vladimir E. Frankevich; Evgeny N. Nikolaev; Gennady T. Sukhikh

    The mass spectrometry‐based molecular profiling can be used for better differentiation between normal and cancer tissues and for the detection of neoplastic transformation, which is of great importance for diagnostics of a pathology, prognosis of its evolution trend, and development of a treatment strategy. The aim of the present study is the evaluation of tissue classification approaches based on various data sets derived from the molecular profile of the organic solvent extracts of a tissue. A set of possibilities are considered for the orthogonal projections to latent structures discriminant analysis: all mass spectrometric peaks over 300 counts threshold, subset of peaks selected by ranking with support vector machine algorithm, peaks selected by random forest algorithm, peaks with the statistically significant difference of the intensity determined by the Mann‐Whitney U test, peaks identified as lipids, and both identified and significantly different peaks. The best predictive potential is obtained for OPLS‐DA model built on nonpolar glycerolipids (Q2 = 0.64, area under curve [AUC] = 0.95); the second one is OPLS‐DA model with lipid peaks selected by random forest algorithm (Q2 = 0.58, AUC = 0.87). Moreover, models based on particular molecular classes are more preferable from biological point of view, resulting in new explanatory mechanisms of pathophysiology and providing a pathway analysis. Another promising features for OPLS‐DA modeling are phosphatidylethanolamines (Q2 = 0.48, AUC = 0.86).

    更新日期:2020-01-14
  • Mass spectrometry and planetary exploration: A brief review and future projection
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-11-28
    Ricardo Arevalo; Ziqin Ni; Ryan M. Danell

    Since the inception of mass spectrometry more than a century ago, the field has matured as analytical capabilities have progressed, instrument configurations multiplied, and applications proliferated. Modern systems are able to characterize volatile and nonvolatile sample materials, quantitatively measure abundances of molecular and elemental species with low limits of detection, and determine isotopic compositions with high degrees of precision and accuracy. Consequently, mass spectrometers have a rich history and promising future in planetary exploration. Here, we provide a short review on the development of mass analyzers and supporting subsystems (eg, ionization sources and detector assemblies) that have significant heritage in spaceflight applications, and we introduce a selection of emerging technologies that may enable new and/or augmented mission concepts in the coming decades.

    更新日期:2020-01-14
  • Geographical discrimination of Chinese winter wheat using volatile compound analysis by HS‐SPME/GC‐MS coupled with multivariate statistical analysis
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-16
    Syed Abdul Wadood; Guo Boli; Zhang Xiaowen; Ali Raza; Wei Yimin

    This study aimed to develop a potential analytical method to discriminate the Chinese winter wheat according to geographical origin and cultivars. A total of 90 wheat samples of 10 different wheat cultivars among three regions were examined by headspace solid phase microextraction coupled with gas chromatography‐mass spectrometry (GC‐MS). The peak areas of 32 main volatile compounds were selected and subjected to statistical analysis, which revealed significant differences among different regions and cultivars. Multivariate analysis of variance showed a significant influence of regions, wheat genotypes, and their interaction on the volatile composition of wheat. Principal component analysis of the aromatic profile showed better visualization for wheat geographical origins. Finally, a classification model based on the linear discriminant analysis was successfully constructed for the discrimination of regions and cultivars with the correct classification percentages of 90 and 100%, respectively.

    更新日期:2020-01-13
  • Multi‐class and multi‐residue screening of veterinary drugs and pesticides in infant formula using Quadrupole‐Orbitrap MS with PRM scan mode
    J. Mass Spectrom. (IF 2.267) Pub Date : 2020-01-09
    Lu‐Qi Zhang; Xiao‐Mei Zhang; Hong‐Wei Zhang; Hui Wang; Hui Xu; Feng‐Mei Wang; Chao Lin; Jing Xiao; Wen‐Yuan Xu

    A multi‐class and multi‐residue method for screening veterinary drugs and pesticides in infant formula was developed and validated using ultra high‐performance liquid chromatograph coupled to Quadrupole‐Orbitrap high resolution mass spectrometry (LC‐HRMS). A total of 49 veterinary drugs and pesticides investigated belong to 11 classes including antivirals, anticoccidials, macrolides, pyrethroids, insecticides, sulfonamides, beta‐agonists, sedatives, thyreostats, non‐steroidal anti‐inflammatory drugs and other pharmacologically active substances. A generic sample preparation and highly selective acquisition mode of parallel reaction monitoring (PRM) were deliberately incorporated to perform efficient screening analysis. As a result, the screening target concentrations of the analytes varied from 1 μg/kg to 500 μg/kg with ≤5% of false compliant rate as specified in Decision 2002/657/EC for screening analysis. The average recoveries ranged from 40.7% to 124.9% as well as the RSDs from 4.2% to 26.6% respectively. The matrix effects and interferences were effectively controlled by integrated application of dispersive solid phase extraction, PRM scan mode, and matrix‐matched standard calibration. The proposed method will be helpful to provide applicable strategy for screening residues in infant formula with surveillance purpose.

    更新日期:2020-01-10
  • Development of supercritical fluid chromatography coupled with mass spectrometry method for characterization of a nonionic surfactant and comparison to liquid chromatography coupled with mass spectrometry method
    J. Mass Spectrom. (IF 2.267) Pub Date : 2020-01-09
    Jinheng Pan; Yan Tang; Zhengchao Shen; Zhenxia Du

    The supercritical fluid chromatography coupled with mass spectrometry method (SFC‐MS) and liquid chromatography coupled with mass spectrometry (LC‐MS) method were developed for the separation and characterization of poly (ethylene oxide) methyl glucose sesquistearate (PEO‐Glu‐Sesquistearate). The products of PEO‐Glu‐Sesquistearate are composed of complex oligomers. The relationship between molecular structure of these oligomers and chromatographic retention behavior in both SFC and LC were discussed and compared. As compared to LC, hydrophobic moieties of compounds favor the fast elution in SFC. The different series can be better separated by LC, while the homologues compounds in same series can be better separated by SFC, and SFC‐MS provided more comprehensive structural information. Different series such as PEO‐distearate, PEO‐stearate, PEO, PEO‐Glu‐tetrastearate, PEO‐Glu‐tristearate, PEO‐Glu‐distearate, PEO‐Glu‐stearate, PEO‐Glu were identified by MS/MS.

    更新日期:2020-01-10
  • Fragmentation pathways of protonated coumarin by ESI‐QE‐ Orbitrap‐MS/MS coupled with DFT calculations
    J. Mass Spectrom. (IF 2.267) Pub Date : 2020-01-08
    Changhai Sun; Yazhuo Wang; Shiyuan Sun; Xin Chen; XinLei Shi; Hongzhuang Fang; Yu Zhang; Zhou Fang

    Coumarin is one of the basic structures of naturally oxygen heterocyclic compound, which was investigated in this paper for its gas‐phase fragmentation behaviors using electrospray quadrupole extractive orbitrap mass spectrometry in the positive mode. The possible fragmentation pathways were proposed based on ESI‐MS/MS data and theory calculation. The elimination of two CO and CO2 were observed for protonated coumarin, which was followed by the formation of a stabilized seven‐member, six‐member and five‐member ring carbocation by loss of C2H2. The possible protonation sites occurred at oxygen 11 atom of coumarin was the main fragmentation pathways. The relative abundance of characteristic fragment ions and the energy‐resolved breakdown curves were used to confirm the cleavage mechanism of protonated coumarin. The methodology and results of present work would contribute to the chemical structure identification of other coumarins.

    更新日期:2020-01-09
  • The characterization of column heating effect in nanoflow liquid chromatography mass spectrometry (nanoLC‐MS)–based proteomics
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-16
    Bolin Li; Fang Guo; Hao Hu; Ping Liu; Minjia Tan; Jianyi Pan; Linhui Zhai

    Column heating strategy is often applied in nano–high‐performance liquid chromatography–mass spectrometer (nanoHPLC‐MS) platform for enhancing the analytical efficiency of peptides or proteins. Nonetheless, the influence effects of column heating in peptides or proteins identification still lack of deep understanding. In this study, a systematic comparison of room temperature (RT) and column heating of nanoHPLC was done. Based on the data, under column heating condition, the backpressure of nanoHPLC can be decreased. Due to the increase of resolution, the peak widths of precursor ion were narrowed. As a result, in MS/MS data acquisition part, more time was spared for MS1 detecting and MS2 fragmenting, which eventually resulted in increased identification of peptides and proteins. Moreover, we also proposed the application scope of column heating by evaluating its influence on sample detection. On one hand, column heating significantly increased the identification of membrane proteins due to more efficient elution of highly hydrophobic peptides compared with RT. On the other hand, heating was not suitable for analyzing short or/and hydrophilic peptides with low retention time, which would be eluted out during sample loading process under high temperature and missed by mass spectrometric detection. In conclusion, our study provides a reference for rational application of column heating in proteomics research.

    更新日期:2020-01-09
  • Cover Picture
    J. Mass Spectrom. (IF 2.267) Pub Date : 2020-01-07
    更新日期:2020-01-08
  • The Kendrick analysis for polymer mass spectrometry
    J. Mass Spectrom. (IF 2.267) Pub Date : 2020-01-07
    Thierry N. J. Fouquet
    更新日期:2020-01-08
  • The Kendrick analysis for polymer mass spectrometry
    J. Mass Spectrom. (IF 2.267) Pub Date : 2020-01-07
    Thierry N.J. Fouquet

    The mass spectrum of a polymer often displays repetitive patterns with peak series spaced by the repeating unit(s) of the polymeric backbones, sometimes complexified with different adducts, chain terminations, or charge states. Exploring the complex mass spectral data or filtering the unwanted signal is tedious whether performed manually or automatically. In contrast, the now 60‐year‐old Kendrick (mass defect) analysis, when adapted to polymer ions, produces visual two‐dimensional maps with intuitive alignments of the repetitive patterns and favourable deconvolution of features overlaid in the one‐dimensional mass spectrum. This special feature article reports on an up‐to‐date and theoretically sound use of Kendrick plots as a data processing tool. The approach requires no prior knowledge of the sample but offers promising dynamic capabilities for visualizing, filtering, and sometimes assigning congested mass spectra. Examples of applications of the approach to polymers are discussed throughout the text, but the same tools can be readily extended to other applications, including the analysis of polymers present as pollutants/contaminants, and to other analytes incorporating a repetitive moiety, for example, oils or lipids. In each of these instances, data processing can benefit from the application of an updated and interactive Kendrick analysis.

    更新日期:2020-01-08
  • Further studies on the signal enhancement effect in laser diode thermal desorption‐triple quadrupole mass spectrometry using microwell surface coatings
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-11
    Alexia Gravel; Cassandra Guérette; Daniel Fortin; Serge Auger; Pierre Picard; Pedro A. Segura

    The laser diode thermal desorption (LDTD) ionization source allows ultrafast and sensitive analysis of small molecules by mass spectrometry. Signal enhancement in LDTD has been observed when coating the surface of sample microwells with a solution of ethylenediaminetetraacetic acid (EDTA) or nitrilotriacetic acid. Here we present a quantitative analysis of signal enhancement using solutions of diverse commercial proteins (lysozyme, immunoglobulin G, albumin, and fibrinogen) as coatings. Results showed that compounds with polar chemical functions such as carboxylic acid, sulfonyl, and nitro had signal enhancement factors, in most cases higher than 10, when using any of the tested proteins as coating agent. Analysis of variance revealed that immunoglobulin G and fibrinogen gave the best results. However, the signal enhancement factors obtained with these proteins were not superior to those observed with EDTA. To explain the signal enhancement effect of proteins, analysis by scanning electron microscopy of dried samples on the microwell sample plates was carried out. Images showed that salicylic acid, one of the compounds with the highest observed signal enhancement, formed a thick layer when applied directly on the uncoated surface, but it formed small crystals (<1 μm) in the presence of protein or EDTA coatings. Further crystallographic studies using powder X‐ray diffraction showed that the crystalline form of salicylic acid is modified in the presence of EDTA. Salicylic acid when mixed with EDTA had a higher percentage of amorphous phase (38.1%) than without EDTA (23.1%). These results appear to confirm that the diminution of crystal size of analytes and the increase of amorphous phase are implicated in signal enhancement effect observed in LDTD using microwell surface coatings. To design better coatings and completely elucidate the signal enhancement effect in LDTD, more studies are necessary to understand the effects of coatings on the ionization of analytes.

    更新日期:2020-01-08
  • Toward high pressure miniature protein mass spectrometer: Theory and initial results
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-11-28
    Chenyue Hou; Qian Xu; Fei Zhang; Ting Jiang; Wei Xu

    Current miniature mass spectrometers mainly focus on the analyses of organic and small biological molecules. In this study, we explored the possibility of developing high resolution miniature ion trap mass spectrometers for whole protein analysis. Theoretical derivation, GPU assisted ion trajectory simulation, and initial experiments on home‐developed “brick” mass spectrometer were carried out. Results show that ion‐neutral collisions have smaller damping effect on large protein ions, and a higher buffer gas pressure should be applied during ion trap operations for protein ions. As a result, higher pressure ion trap operation not only benefits instrument miniaturization, but also improves mass resolution of protein ions. Dynamic mass scan rate and generation of low charge state protein ions are also found to be helpful in terms of improving mass resolutions. Theory and conclusions found in this work are also applicable in the development of benchtop mass spectrometers.

    更新日期:2020-01-08
  • Improved MALDI‐MS method for the highly sensitive and reproducible detection of biomarker peaks for the proteotyping of Salmonella serotypes
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-11-27
    Yuko Fukuyama; Teruyo Ojima‐Kato; Satomi Nagai; Keisuke Shima; Shinji Funatsu; Yoshihiro Yamada; Hiroto Tamura; Shizuo Nomura; Koretsugu Ogata; Sadanori Sekiya; Shinichi Iwamoto; Koichi Tanaka

    The rapid identification and classification of pathogenic microorganisms, including Salmonella enterica, is important for the surveillance and prevention of foodborne diseases. Matrix‐assisted laser desorption\ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) has been shown to be an effective tool for the rapid identification of microorganisms. In a previous report, a mass database consisting of 12 biomarker proteins, S8, L15, L17, L21, L25, S7, superoxide dismutase (SodA), peptidylprolyl cis‐trans isomerase C, Gns, YibT, YaiA, and YciF, was introduced for the serotyping of S. enterica via MALDI‐MS (Applied Microbiology and Biotechnology, 2017, 101, 8557‐8569). However, the reproducibility of peak detection of biomarkers such as SodA at m\z 23 000 was poor. We report here an optimized MALDI‐MS method for detecting these biomarkers with high sensitivity and reproducibility. The issue was solved by controlling the bacterial concentration at 1 × 10 to 1 × 102 MFU (3 × 106 to 3 × 107 CFU\μL, as calculated from the MFU), using the colony suspension supernatant obtained by centrifugation, and using matrix additives such as methylenediphosphonic acid and N‐decyl‐β‐D‐maltopyranoside. We propose that the method including the above steps is one of the best for detecting biomarkers with high sensitivity and reproducibility.

    更新日期:2020-01-08
  • Olefinic reagents tested for peptide derivatization with switchable properties: Stable upon collision induced dissociation and cleavable by in‐source Paternò‐Büchi reactions
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-11-28
    Patrick Esch; Moritz Fischer; Sven Heiles; Mathias Schäfer

    This contribution is part of our ongoing efforts to develop innovative cross‐linking (XL) reagents and protocols for facilitated peptide mixture analysis and efficient assignment of cross‐linked peptide products. In this report, we combine in‐source Paternò‐Büchi (PB) photo‐chemistry with a tandem mass spectrometry approach to selectively address the fragmentation of a tailor‐made cross‐linking reagent. The PB photochemistry, so far exclusively used for the identification of unsaturation sites in lipids and in lipidomics, is now introduced to the field of chemical cross‐linking. Based on trans‐3‐hexenedioic acid, an olefinic homo bifunctional amine reactive XL reagent was designed and synthesized for this proof‐of‐principle study. Condensation products of the olefinic reagent with a set of exemplary peptides are used to test the feasibility of the concept. Benzophenone is photochemically reacted in the nano‐electrospray ion source and forms oxetane PB reaction products. Subsequent CID‐MS triggered retro‐PB reaction of the respective isobaric oxetane molecular ions and delivers reliably and predictably two sets of characteristic fragment ions of the cross‐linker. Based on these signature ion sets, a straightforward identification of covalently interconnected peptides in complex digests is proposed. Furthermore, CID‐MSn experiments of the retro‐PB reaction products deliver peptide backbone characteristic fragment ions. Additionally, the olefinic XL reagents exhibit a pronounced robustness upon CID‐activation, without previous UV‐excitation. These experiments document that a complete backbone fragmentation is possible, while the linker‐moiety remains intact. This feature renders the new olefinic linkers switchable between a stable, noncleavable cross‐linking mode and an in‐source PB cleavable mode.

    更新日期:2020-01-08
  • Elucidation of artefacts in proton transfer reaction time‐of‐flight mass spectrometers
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-11
    Jorge Iván Salazar Gómez; Christian Klucken; Martha Sojka; Liudmyla Masliuk; Thomas Lunkenbein; Robert Schlögl; Holger Ruland

    We present an effective procedure to differentiate instrumental artefacts, such as parasitic ions, memory effects, and real trace impurities contained in inert gases. Three different proton transfer reaction mass spectrometers were used in order to identify instrument‐specific parasitic ions. The methodology reveals new nitrogen‐ and metal‐containing ions that up to date have not been reported. The parasitic ion signal was dominated by [N2]H+ and [NH3]H+ rather than by the common ions NO+ and O2+. Under dry conditions in a proton transfer reaction quadrupole interface time‐of‐flight mass spectrometer (PTR‐QiTOF), the ion abundances of [N2]H+ were elevated compared with the signals in the presence of humidity. In contrast, the [NH3]H+ ion did not show a clear humidity dependency. On the other hand, two PTR‐TOF1000 instruments showed no significant contribution of the [N2]H+ ion, which supports the idea of [N2]H+ formation in the quadrupole interface of the PTR‐QiTOF. Many new nitrogen‐containing ions were identified, and three different reaction sequences showing a similar reaction mechanism were established. Additionally, several metal‐containing ions, their oxides, and hydroxides were formed in the three PTR instruments. However, their relative ion abundancies were below 0.03% in all cases. Within the series of metal‐containing ions, the highest contribution under dry conditions was assigned to the [Fe(OH)2]H+ ion. Only in one PTR‐TOF1000 the Fe+ ion appeared as dominant species compared with the [Fe(OH)2]H+ ion. The present analysis and the resulting database can be used as a tool for the elucidation of artefacts in mass spectra and, especially in cases, where dilution with inert gases play a significant role, preventing misinterpretations.

    更新日期:2020-01-08
  • An Inexpensive, simple calibration method for MALDI TOF/TOF systems
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-11-27
    Matthew B. O'Rourke; Matthew P. Padula

    The array of analytes that can be measured by MADLI MS has created an equally vast range of calibration mixtures. The inherent problem with this is that acquiring all of them at commercial rates can be prohibitively expensive. With this in mind, we have created a low‐cost alternative to the most commonly used peptide calibrants.

    更新日期:2020-01-08
  • Applicability of MALDI‐TOF MS for determination of quinolone residues in fish
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-11-27
    Patrícia A. de C. Braga; Marcos N. Eberlin; Felix G.R. Reyes

    MALDI‐TOF MS approach for determination of six quinolones residues in fillets of pangasius (Pangasionodon hypophthalmus) was studied, considering that is a very sensitive analytical technique with simple and high‐throughput operation, contributing to knowledge regarding application of this technique to the determination of small‐molecular‐weight organic compound residues in foods. LIFT‐MS/MS showed to be a successful approach to identify the presence of all quinolone residues in the fish fillet, at their respective MRL level. This study opens an important field of research for the development of simple and high‐throughput bioanalytical screening methods for the determination of veterinary drug residues in foods.

    更新日期:2020-01-08
  • Cover Picture
    J. Mass Spectrom. (IF 2.267) Pub Date : 2020-01-06
    更新日期:2020-01-07
  • Tutorial and comprehensive computational study of acceptance and transmission of sinusoidal and digital ion guides
    J. Mass Spectrom. (IF 2.267) Pub Date : 2020-01-06
    Adam P. Huntley; Gregory F. Brabeck; Peter T.A. Reilly
    更新日期:2020-01-07
  • Tutorial and comprehensive computational study of acceptance and transmission of sinusoidal and digital ion guides
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-11-25
    Adam P. Huntley; Gregory F. Brabeck; Peter T.A. Reilly

    A quadrupoles acceptance is a measure of its ability to catch ions with certain trajectories. One way to calculate acceptance is the method of ellipses. The method arose partly from a simplification that trajectories could be calculated for an electrode axis independently of others. It has been used to calculate the acceptance and transmission of sine‐driven quadrupole mass filters for over 50 years. Although the method is straightforward, it is generally described with little detail or presented as a confusing string of equations. As such, it may not be decipherable by all practitioners. For this reason, the first half of this paper presents a practical explanation of the method of ellipses and the concepts that make it work. Only equations necessary to describe the method are introduced. The tutorial also prepares the reader for the second half, which presents an alternative approach for calculating acceptance based on an array of initial trajectories. The alternative approach is used to compare the acceptance of simplified sinusoidal and digital ion guides. The method of ellipses was applied to validate results of the new approach for calculation of acceptance.

    更新日期:2020-01-07
  • Fragmentation pathways of deprotonated amide‐sulfonamide CXCR4 inhibitors investigated by ESI‐IT‐MSn, ESI‐Q‐TOF‐MS/MS and DFT calculations
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-11-20
    Zili Guo; Xiaokang Jie; Peixi Zhu; Jian Sun; Jinping Gu; Feng Su; Renren Bai; Yuanyuan Xie

    Amide‐sulfonamides provide a potent anti‐inflammatory scaffold targeting the CXCR4 receptor. A series of novel amide‐sulfonamide derivatives were investigated for their gas‐phase fragmentation behaviors using electrospray ionization ion trap mass spectrometry and quadrupole time‐of‐flight mass spectrometry in negative ion mode. Upon collision‐induced dissociation (CID), deprotonated amide‐sulfonamides mainly underwent either an elimination of the amine to form the sulfonyl anion and amide anion or a benzoylamide derivative to provide sulfonamide anion bearing respective substituent groups. Based on the characteristic fragment ions and the deuterium–hydrogen exchange experiments, three possible fragmentation mechanisms corresponding to ion‐neutral complexes including [sulfonyl anion/amine] complex (INC‐1), [sulfonamide anion/benzoylamide derivative] complex (INC‐2) and [amide anion/sulfonamide] complex (INC‐3), respectively, were proposed. These three ion‐neutral complexes might be produced by the cleavages of S–N and C–N bond from the amide‐sulfonamides, which generated the sulfonyl anion (Route 1), sulfonamide anion (Route 2) and the amide anion (Route 3). DFT calculations suggested that Route 1, which generated the sulfonyl anion (ion c) is more favorable. In addition, the elimination of SO2 through a three‐membered‐ring transition state followed by the formation of C–N was observed for all the amide‐sulfonamides.

    更新日期:2020-01-07
  • A simple MALDI target plate with channel design to improve detection sensitivity and reproducibility for quantitative analysis of biomolecules
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-11-08
    Zhen Liu; Peng Zhang; Lars Kästner; Dietrich A. Volmer

    Overcoming the detrimental effects of sweet spots during crystallization is an important step to improve the quantitative abilities of matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry. In this study, we introduce MALDI targets, which exhibit a channel design to reduce sweet spot phenomena and improve reproducibility. The size of the channels was 3.0 mm in length, 0.35 mm in depth, and 0.40 mm in width, adjusted to the width of the implemented laser beam. For sample deposition, the matrix/sample mixture was homogenously deposited into the channels using capillary action. To demonstrate the proof‐of‐principle, the novel plates were used for the quantification of acetyl‐L‐carnitine in human blood plasma using a combined standard addition and isotope dilution method. The results showed that the reproducibility of acetyl‐L‐carnitine detection was highly improved over a conventional MALDI‐MS assay, with RSD values of less than 5.9% in comparison with 15.6% using the regular MALDI method. The limits of quantification using the new plates were lowered approximately two‐fold in comparison with a standard rastering approach on a smooth stainless‐steel plate. Matrix effects were also assessed and shown to be negligible. The new assay was subsequently applied to the quantification of acetyl‐L‐carnitine in human plasma samples.

    更新日期:2020-01-07
  • CTP synthetase activity assay by liquid chromatography tandem mass spectrometry in the multiple reaction monitoring mode
    J. Mass Spectrom. (IF 2.267) Pub Date : 2020-01-06
    Anne‐Claire Boschat; Norbert Minet; Emmanuel Martin; Robert Barouki; Sylvain Latour; Sylvia Sanquer

    Cytidine 5′‐triphosphate synthetase (CTPS) is known to be a central enzyme in the de novo synthesis of CTP. We have recently demonstrated that a deficiency in CTPS1 is associated with an impaired capacity of activated lymphocytes to proliferate leading to a combined immunodeficiency disease. In order to better document its role in immunomodulation, we developed a method for measuring CTPS activity in human lymphocytes. Using liquid chromatography‐mass spectrometry, we quantified CTPS activity by measuring CTP in cell lysates. A stable isotope analog of CTP served as internal standard. We characterized the kinetic parameters Vmax and Km of CTPS and verified that an inhibition of the enzyme activity was induced after 3‐deazauridine (3DAU) treatment, a known inhibitor of CTPS. We then determined CTPS activity in healthy volunteers, in a family whose child displayed a homozygous mutation in CTPS1 gene and in patients who had developed or not a chronic lung allograft dysfunction (CLAD) after lung transplantation. Linearity of the CTP determination was observed up to 451 μmol/L, with accuracy in the 15% tolerance range. Michaelis‐Menten kinetics for lysates of resting cells were Km=280±310 μmol/L for UTP, Vmax=83±20 pmol/min and, for lysates of activated PBMCs, Km=230±280 μmol/L for UTP, Vmax=379±90 pmol/min. Treatment by 3DAU and homozygous mutation in CTPS1 gene abolished the induction of CTPS activity associated with cell stimulation, and CTPS activity was significantly reduced in the patients who developed CLAD. We conclude that this test is suitable to reveal the involvement of CTPS alteration in immunodeficiency.

    更新日期:2020-01-07
  • Singlet oxygen‐induced protein aggregation: Lysozyme crosslink formation and nLC‐MS/MS characterization
    J. Mass Spectrom. (IF 2.267) Pub Date : 2020-01-06
    Emerson Finco Marques; Marisa H.G. Medeiros; Paolo Di Mascio

    Singlet molecular oxygen (1O2) has been associated with a number of physiological processes. Despite the recognized importance of 1O2‐mediated protein modifications, little is known about the role of this oxidant in crosslink formation and protein aggregation. Thus, using lysozyme as a model, the present study sought to investigate the involvement of 1O2 in crosslink formation. Lysozyme was photochemically oxidized in the presence of rose bengal or chemically oxidized using [18O]‐labeled 1O2 released from thermolabile endoperoxides. It was concluded that both 1O2 generating systems induce lysozyme crosslinking and aggregation. Using SDS‐PAGE and nano‐scale liquid chromatography coupled to electrospray ionization mass spectrometry, the results clearly demonstrated that 1O2 is directly involved in the formation of covalent crosslinks involving the amino acids histidine, lysine, and tryptophan.

    更新日期:2020-01-07
  • Using spectral matching to interpret LC‐MS/MS data during RNA modification mapping
    J. Mass Spectrom. (IF 2.267) Pub Date : 2020-01-06
    Mellie June Paulines; Collin Wetzel; Patrick A. Limbach

    While a number of approaches have been developed to analyze liquid chromatography tandem mass spectrometry (LC‐MS/MS) data obtained from modified oligonucleotides, the majority of these methods require analyzing every MS/MS spectrum de novo to sequence the oligonucleotide and place the modification. Spectral matching is an alternative approach for analyzing MS/MS data that is based on creating a library of annotated MS/MS spectra against which individual MS/MS data can be searched. Here, we have adapted the existing NIST spectral matching software to enable its use in the interpretation of MS/MS data obtained from modified oligonucleotides. In particular, we demonstrate the utility of this approach to identify specific post‐transcriptionally modified nucleosides in particular transfer RNAs (tRNAs) obtained through a conventional RNA modification mapping experimental protocol. Spectral matching was found to be an efficient approach for screening for known modified tRNAs by using the experimental data as the library and previously annotated RNase T1 digestion products of tRNAs as the reference spectra. The utility of spectral matching for rapid analysis of multiple LC‐MS/MS analyses was demonstrated by screening mutant strains of Streptococcus mutans to identify the enzyme(s) responsible for synthesizing the tRNA position 37 modification threonylcarbamoyladenosine (t6A).

    更新日期:2020-01-07
  • ESI‐QTof‐MS characterization of hirsutinolide and glaucolide sesquiterpene lactones: Fragmentation mechanisms and differentiation based on Na+/H+ adducts interactions in complex mixture
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-17
    Layzon A.L. da Silva; Louis P. Sandjo; Alechania Misturini; Giovanni F. Caramori; Maique W. Biavatti

    Sesquiterpene lactones (SL) have been reported with various biological effects. Among the described SL skeletons, hirsutinolide and glaucolide have not been extensively studied by mass spectrometry (MS), especially how to distinguish them in organic matrices. Thus, this paper reports (1) a strategy of their differentiation based on MS behavior during the ionization and (2) a proposal of the fragmentation pattern for both SL‐subtypes. ESI(+)‐HRMS data of four isolated SL (hirsutinolides 1 and 3; glaucolides 2 and 4) were recorded by direct and UPLC water‐sample combined injections. These analyses revealed that hirsutinolides and glaucolides formed [M+Na]+ ion during the operation of the direct MS injection, and ([M+Na]+ and [M+H‐H2O]+) and [M+H]+ ions were respectively observed for hirsutinolides and glaucolides during the operation of combined UPLC water and sample MS injection. Computational simulations showed that the complex hirsutinolide (1)‐Na+ formed with a lower preparation energy compared with the complex glaucolide (2)‐Na+. However, despite their different behavior during the ionization process, ESI(+)‐HRMS/MS analyses of 1‐4 gave similar fragmentation patterns at m/z 277, 259, 241, and 231 that can be used as diagnostic ions for both skeletons. Moreover, the differentiation strategy based on the nature of the complex SL‐adducts and their MS/MS fragmentation pattern were successfully applied for the chemical characterization of the extract from Vernonanthura tweedieana using UPLC‐ESI‐HRMS/MS. Among the characterized metabolites, SL with hirsutinolide and glaucolide skeletons showed the aforementioned diagnostic fragments and an ionization behavior that was similar to those observed during the water‐sample combined injection.

    更新日期:2020-01-07
  • Development of two‐dimensional gas chromatography (GC×GC) coupled with Orbitrap‐technology‐based mass spectrometry (MS)–Interest in the identification of bio‐fuel composition
    J. Mass Spectrom. (IF 2.267) Pub Date : 2020-01-05
    Nguyen Viet Hung; Chetna Mohabeer; Marie Vaccaro; Stéphane Marcotte; Valérie Agasse‐Peulon; Lokmane Abdelouahed; Bechara Taouk; Pascal Cardinael

    Comprehensive Gas Chromatography (GC) has emerged in recent years as the technique of choice for the analysis of volatile and semi‐volatile compounds in complex matrices. Coupling it with high‐resolution mass spectrometry makes a powerful tool for identification and quantification of organic compounds. The results obtained in this study showed a significant improvement by using GC×GC‐EI‐MS in comparison with GC‐EI‐MS; the separation of chromatogram peaks was highly improved, which facilitated detection and identification. However, the limitation of Orbitrap mass analyzer compared to TOF analyzer is the data acquisition rate; the frequency average was about 25 Hz at a mass resolving power of 15.000, which is barely sufficient for the proper reconstruction of the narrowest chromatographic peaks. On the other hand, the different spectra obtained in this study showed an average mass accuracy of about 1 ppm. Within this average mass accuracy, some reasonable elemental compositions can be proposed and combined with characteristic fragment ions, the molecules can be identified with precision. At a mass resolving power of 7.500, the scan rate reaches 43 Hz and the GC×GC‐MS peaks can be represented by more than 10 data points, which should be sufficient for quantification. The GC×GC‐MS was also applied to analyze a cellulose bio‐oil sample. Following this, a highly resolved chromatogram was obtained, allowing EI mass spectra containing molecular and fragment ions of many distinct molecules present in the sample to be identified.

    更新日期:2020-01-06
  • Lipid Mass Spectrometry: A Path Traveled for 50 Years
    J. Mass Spectrom. (IF 2.267) Pub Date : 2020-01-02
    Robert C. Murphy

    In the middle of the 1960s, I began graduate school and at the same time started on the path of using mass spectrometry to gain insight into various aspects of lipid biochemistry. This was not a straight path but one that went from organic geochemistry, to lunar sample analysis, to a pursuit of the structure of an elusive and very active, lipid mediator slow reacting substance of anaphylaxis (SRS‐A). The discovery of the structure of SRS‐A opened important questions about phospholipid biochemistry and the arachidonate cycle in cells. I have written this reflection to highlight the various advances in mass spectrometry that occurred during this time that had a great impact on our ability to study lipid biochemistry. I specifically applied these new advances to studies of leukotriene biosynthesis in vivo, leukotriene metabolism, and arachidonate‐containing phospholipids that are essential in providing arachidonic acid for the 5‐lipoxygenase pathway. Along the way imaging mass spectrometry was shown to be a powerful tool to probe lipids as they exist in tissue slices. We found this as just one of the ways to use the emerging technology of lipidomics to study human pathophysiology. Our studies of neutral lipids and oxidized phospholipids were especially challenging due to the total number of molecular species that could be found in cells. Many challenges remain in using mass spectrometry for lipid studies and a few are presented.

    更新日期:2020-01-04
  • ToF‐SIMS spectrometry to observe fatty acid profiles of breast tissues in broiler chicken subjected to varied vegetable oil diet
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-30
    Magdalena E. Marzec; Dorota Wojtysiak; Katarzyna Połtowicz; Joanna Nowak

    This study is aimed to observe changes in fatty acid profiles by time of flight secondary ion mass spectrometry (ToF‐SIMS) in breast muscle tissues of broilers. Four different groups were identified. The source of fat in group I was soy oil (rich in linoleic acid, ω‐6), group II received linseed oil (ω‐3), and the third group was fed a mixture of the two mentioned oils. Broilers in the control group were fed with beef tallow, used in mass commercial production. The results reveal that the use of vegetable oils in animal nutrition determines the lipid profile of fatty acids. ToF‐SIMS measurements showed that the lipid profile of muscle fibers and intramuscular fat reflect the composition of fats used as feed additives. In both structures, the ratio of ω‐6/ω‐3 fatty acids, which is most favorable for human health, was found in the groups in which a mixture of vegetable oils and a supplement of linseed oil were used.

    更新日期:2019-12-30
  • The Perspectives of Ethanol Usage as an Internal Standard for the Quantification of Volatile Compounds in Alcoholic Products by GC‐MS
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-27
    Anton Korban; Siarhei Charapitsa; Radomír Čabala; Lidia Sobolenko; Svetlana Sytova

    The potential use of ethanol as an internal standard (IS) for GC‐MS analysis was studied. The paper describes the analysis of spirit drinks and other alcoholic products which consist of a mixture of water, ethanol and volatile compounds. In the suggested method, ethanol was employed as an IS for the common procedure of volatile compounds quantification. A number of standard solutions of 9 compounds with different concentrations was prepared in a water‐ethanol matrix and measured with GC‐MS in the SIM mode. Two possible approaches were suggested to avoid detector saturation during ethanol detection. The first one consisted in using less abundant m/z 47 as quantifiers. These ions mainly correspond to unfragmented heavy ethanol molecules containing one 13C isotope. The second method consisted in reduction of the voltage of MS electron multiplier. The experiment also included the preparation and subsequent dilution of the standard solution and ethanol with water, which determined the linearity of the modified MS response relative to the ethanol content. Analysis of the obtained results revealed that volatile compounds can be successfully accurately determined with GC‐MS by employing ethanol as an IS. Application of the suggested method is not limited to the reported volatile compounds and alcoholic products.

    更新日期:2019-12-29
  • Comparison of the pH‐dependent formation of His and Cys heptapeptide complexes of nickel (II), copper (II), and zinc (II) as determined by ion mobility – mass spectrometry
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-27
    Enas N. Yousef; Laurence A. Angel

    The analog methanobactin (amb) peptide with the sequence ac‐His1‐Cys2‐Gly3‐Pro4‐Tyr5‐His6‐Cys7 (amb5A) will bind the metal ions of zinc, nickel, and copper. To further understand how amb5A binds these metals we have undertaken a series of studies of structurally related heptapeptides where one or two of the potential His or Cys binding sites have been replaced by Gly, or the C‐terminus has been blocked by amidation. The studies were designed to compare how these metals bind to these sequences in different pH solutions of pH 4.2 to 10 and utilized native electrospray ionization (ESI) with ion mobility – mass spectrometry (IM‐MS) which allows for the quantitative analysis of the charged species produced during the reactions. The native ESI conditions were chosen to conserve as much of the solution‐phase behavior of the amb peptides as possible and an analysis of how the IM‐MS results compare with the expected solution‐phase behavior is discussed. The oligopeptides studied here have applications for tag‐based protein purification methods, as therapeutics for diseases caused by elevated metal ion levels or as inhibitors for metal‐protein enzymes such as matrix metalloproteinases.

    更新日期:2019-12-29
  • Defining the Human Kidney N‐Glycome in Normal and Cancer Tissues Using MALDI Imaging Mass Spectrometry
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-20
    Richard R. Drake; Colin McDowell; Connor West; Fred David; Thomas W. Powers; Tamara Nowling; Evelyn Bruner; Anand S. Mehta; Peggi M. Angel; Laura A. Marlow; Han W. Tun; John A. Copland

    Clear‐cell renal cell carcinoma (ccRCC) presents challenges to clinical management due to late‐stage detection, treatment resistance and frequent disease recurrence. Metabolically, ccRCC has a well described Warburg effect utilization of glucose, but how this affects complex carbohydrate synthesis and alterations to protein and cell surface glycosylation is poorly defined. Using an imaging mass spectrometry approach, N‐glycosylation patterns and compositional differences were assessed between tumor and non‐tumor regions of formalin‐fixed clinical ccRCC specimens and tissue microarrays. Regions of normal kidney tissue samples were also evaluated for N‐linked glycan‐based distinctions between cortex, medullar, glomeruli and proximal tubule features. Most notable was the proximal tubule localized detection of abundant multi‐antennary N‐glycans with bisecting N‐acetylglucosamine and multiple fucose residues. These glycans are absent in ccRCC tissues, while multiple tumor specific N‐glycans were detected with tri and tetra‐antennary structures and varying levels of fucosylation and sialylation. A polycystic kidney disease tissue was also characterized for N‐glycan composition, with specific non‐fucosylated glycans detected in the cyst fluid regions. Complementary to the imaging mass spectrometry analyses was an assessment of transcriptomic gene array data focused on the fucosyltransferase gene family and other glycosyltransferase genes. The transcript levels of the FUT3 and FUT6 genes responsible for the enzymes that add fucose to N‐glycan antennae were significantly decreased in all ccRCC tissues relative to matching non‐tumor tissues. These striking differences in glycosylation associated with ccRCC could lead to new mechanistic insight into the glycobiology underpinning kidney malignancies and suggest the potential for new therapeutic interventions and diagnostic markers.

    更新日期:2019-12-21
  • Uncovering Matrix Effects on Lipid Analyses in MALDI Imaging Mass Spectrometry Experiments
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-20
    William J. Perry; Nathan Heath Patterson; Boone M. Prentice; Elizabeth K. Neumann; Richard M. Caprioli; Jeffrey M. Spraggins

    The specific matrix used in matrix‐assisted laser desorption/ionization imaging mass spectrometry (MALDI IMS) can have an effect on the molecules ionized from a tissue sample. The sensitivity for distinct classes of biomolecules can vary when employing different MALDI matrices. Here, we compare the intensities of various lipid sub‐classes measured by Fourier transform ion cyclotron resonance (FT‐ICR) IMS of murine liver tissue when using 9‐Aminoacridine (9AA), 5‐Chloro‐2‐mercaptobenzothiazole (CMBT), 1,5‐Diaminonaphthalene (DAN), 2,5‐Dihydroxyacetophenone (DHA), and 2,5‐Dihydroxybenzoic acid (DHB). Principal component analysis and receiver operating characteristic curve analysis revealed significant matrix effects on the relative signal intensities observed for different lipid sub‐classes and adducts. Comparison of spectral profiles and quantitative assessment of the number and intensity of species from each lipid sub‐class showed that each matrix produces unique lipid signals. In positive ion mode, matrix application methods played a role in the MALDI analysis for different cationic species. Comparisons of different methods for the application of DHA showed a significant increase in the intensity of sodiated and potassiated analytes when using an aerosol sprayer. In negative ion mode, lipid profiles generated using DAN were significantly different than all other matrices tested. This difference was found to be driven by modification of phosphatidylcholines during ionization that enables them to be detected in negative ion mode. These modified phosphatidylcholines are isomeric with common phosphatidylethanolamines confounding MALDI IMS analysis when using DAN. These results show an experimental basis of MALDI analyses when analyzing lipids from tissue and allow for more informed selection of MALDI matrices when performing lipid IMS experiments.

    更新日期:2019-12-21
  • Ion trap MS using high trapping gas pressure enables unequivocal structural analysis of three isobaric compounds in a mixture by using Energy‐Resolved Mass Spectrometry and the Survival Yield technique
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-13
    Alicia Maroto; Dany Jeanne Dit Fouque; Antony Memboeuf

    Recently, it has been shown that Energy‐Resolved Mass Spectrometry can provide quantitative information from two isomeric or isobaric compounds in mixtures by using the Survival Yield technique together with “Gas‐Phase Collisional Purification” (GPCP) strategy1. Herein, we present an improvement and an extension of this concept to the structural analysis of a model mixture of three isobaric compounds (two peptides and a polyether). By using default Collision Induced Dissociation (CID) tandem MS parameters on an ion trap instrument, the previous approach did not show any signs of isobaric contamination. However, by modifying CID conditions and using a threefold increase of the He trapping gas pressure (to reach 3.00·10‐5 mbar), the Survival Yield curve was unexpectedly and strongly shifted to higher excitation voltages with two plateaus appearing. Those plateaus, indicating clearly the presence of three isobaric compounds, were taken as reliable indicators to perform GPCP at carefully selected excitation voltages in order to selectively fragment one compound after the other. In this way, CID mass spectra of each compound were correctly recovered, both in terms of fragment ion peaks and relative intensities, from Energy Resolved MSn spectra of the three compounds mixture. This feature enables their unequivocal structural analysis as if samples were free from isobaric interferences. In this paper, we also discuss the possibility for recovering SY curves for pure compounds directly from the mixture. Clearly, in this case, the higher He trapping gas pressure made it possible to use the SY technique, for the first time, for the structural analysis in the case of mixtures of three isobaric compounds. This observation, quite unexpected, demonstrates that the trapping gas pressure is of paramount importance although it is usually not considered in Energy‐Resolved Mass Spectrometry for structural and/or quantitative analysis.

    更新日期:2019-12-17
  • Negative‐ion/positive‐ion coincidence spectroscopy as a tool to identify anionic fragments: The case of core‐excited CHF3
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-11
    A. Kivimäki, C. Stråhlman, R. Sankari, R. Richter

    We have studied the dissociation of the trifluoromethane molecule, CHF3, into negative ionic fragments at the C 1s and F 1s edges. The measurements were performed by detecting coincidences between negative and positive ions. We observed five different negative ions: F‐, H‐, C‐, CF‐, and F2‐. Their production was confirmed by the analysis of triple coincidence events (negative‐ion/positive‐ion/positive‐ion or NIPIPI coincidences) that were recorded with cleaner signals than those of the negative‐ion/positive‐ion coincidences. The intensities of the most intense NIPIPI coincidence channels were recorded as a function of photon energy across the C 1s and F 1s excitations and ionization thresholds. We also observed dissociation channels involving the formation of one negative ion and three positive ions. Our results demonstrate that negative‐ion/positive‐ion coincidence spectroscopy is a very sensitive method to observe anions, which at inner‐shell edges are up to three orders of magnitude less probable dissociation products than cations.

    更新日期:2019-12-11
  • Immersion by Rotation‐Based Application of the Matrix for Fast and Reproducible Sample Preparations and Robust Results in Mass Spectrometry Imaging
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-11
    Johanna Schäfermann, Georg Kliewer, Jan Lösch, Hanna Bednarz, Marco Giampà, Karsten Niehaus

    Automated matrix deposition for matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) is crucial for producing reproducible analyte ion signals. Here we report an innovative method employing an automated immersion apparatus, which enables a robust matrix deposition within 5 minutes and with scalable throughput by using MAPS matrix and non‐polar solvents. MSI results received from mouse heart and rat brain tissues were qualitatively similar to those from nozzle sprayed samples with respect to peak number and quality of the ion images. Overall, the immersion‐method enables a fast and careful matrix deposition and has the future potential for implementation in clinical tissue diagnostics.

    更新日期:2019-12-11
  • Cover Picture
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-10
    更新日期:2019-12-11
  • δ34S for tracing the origin of cheese and detecting its authenticity
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-09
    Silvia Pianezze, Luana Bontempo, Matteo Perini, Agostino Tonon, Luca Ziller, Pietro Franceschi, Federica Camin

    Casein δ34S of 725 samples of cheese from all over the world were measured using IRMS. δ34S alone made it possible to establish characteristic ranges of values for two types of Italian cheese (Grana Padano PDO and Parmigiano Reggiano PDO) and for the different regions and provinces of both the Grana Padano PDO and the Parmigiano Reggiano PDO zones. Moreover, δ34S of PDO Italian samples were compared to both Italian (not PDO) and foreign competitive cheese samples. In all the cases, sulfur isotopic ratio analysis was a powerful tool to fix characteristic ranges of values for cheeses coming from different countries and to improve the information given by other isotopic parameters.

    更新日期:2019-12-09
  • Supercritical fluid chromatography coupled to mass spectrometry for lipidomics
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-09
    Stéphanie Boutet‐Mercey, Laurent Laboureur, Carlos Rincon, Juliette Jouhet, François Fenaille, Benoit Colsch, David Touboul, Céline Chollet, Marie Méjean
    更新日期:2019-12-09
  • Supercritical fluid chromatography coupled to mass spectrometry for lipidomics
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-11-08
    Céline Chollet, Stéphanie Boutet‐Mercey, Laurent Laboureur, Carlos Rincon, Marie Méjean, Juliette Jouhet, François Fenaille, Benoit Colsch, David Touboul

    Supercritical fluid chromatography (SFC) has experienced a particular revival in recent years thanks to the development of robust and efficient commercial systems. Because of its physico‐chemical properties, supercritical carbon dioxide (CO2) mixed with cosolvents and additives is particularly suitable for SFC to allow the elution of compounds of different polarities and more particularly complex lipids. Hyphenation with mass spectrometry (MS) is increasingly described in the literature but still requires many further developments in order to be as user‐friendly as coupling with liquid chromatography. The basic concepts of SFC and MS hyphenation will be first considered. Then a representative example of method development in lipidomics will be introduced. In conclusion, the challenges and future needs in this field of research will be discussed.

    更新日期:2019-12-09
  • Positive and negative ions of the amino acid histidine formed in low‐energy electron collisions
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-11-06
    Rebecca Meißner, Linda Feketeová, Andreas Bayer, Johannes Postler, Paulo Limão‐Vieira, Stephan Denifl

    Histidine is an aromatic amino acid crucial for the biological functioning of proteins and enzymes. When biological matter is exposed to ionising radiation, highly energetic particles interact with the surrounding tissue which leads to efficient formation of low‐energy electrons. In the present study, the interaction of low‐energy electrons with gas‐phase histidine is studied at a molecular level in order to extend the knowledge of electron‐induced reactions with amino acids. We report both on the formation of positive ions formed by electron ionisation and negative ions induced by electron attachment. The experimental data were complemented by quantum chemical calculations. Specifically, the free energies for possible fragmentation reactions were derived for the τ and the π tautomer of histidine to get insight into the structures of the formed ions and the corresponding neutrals. We report the experimental ionisation energy of (8.48 ± 0.03) eV for histidine which is in good agreement with the calculated vertical ionisation energy. In the case of negative ions, the dehydrogenated parent anion is the anion with the highest mass observed upon dissociative electron attachment. The comparison of experimental and computational results was also performed in view of a possible thermal decomposition of histidine during the experiments, since the sample was sublimated in the experiment by resistive heating of an oven. Overall, the present study demonstrates the effects of electrons as secondary particles in the chemical degradation of histidine. The reactions induced by those electrons differ when comparing positive and negative ion formation. While for negative ions, simple bond cleav ages prevail, the observed fragment cations exhibit partly restructuring of the molecule during the dissociation process.

    更新日期:2019-12-09
  • Identification of bifucosylated glycoforms using low‐energy CID spectra
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-10-09
    András Ács, Lilla Turiák, Ágnes Révész, Károly Vékey, László Drahos

    We have used tandem mass spectrometry (MS/MS)‐based analysis of glycopeptides in order to identify the composition and structure of rare glycoforms. The results illustrate utility of low‐energy MS/MS for structure identification. We have shown the presence of bifucosylated and trifucosylated glycoforms in human α‐1‐acid glycoprotein (AGP), a major plasma glycoprotein. Fucosylation in the case of AGP always occurs on the antennae; core fucosylation was not observed.

    更新日期:2019-12-09
  • Solid phase microextraction as a powerful alternative for screening of secondary metabolites in actinomycetes
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-10-18
    Vinicius Ricardo Acquaro Junior, Júlia Pereira Rodrigues, Luiz Alberto Beraldo Moraes

    Actinobacteria are one of the most promising producers of medically and industrially relevant secondary metabolites. However, screening of such compounds in actinobacteria growth demands simple, fast, and efficient extraction procedures that enable detection and precise quantification of biologically active compounds. In this regard, solid phase microextraction (SPME) emerges as an ideal extraction technique for screening of secondary metabolites in bacteria culture due to its non‐exhaustive, minimally invasive, and non‐destructive nature: its integrated sample preparation workflow; balanced coverage feature; metabolism quenching capabilities; and superior cleanup, as well as its versatility in configuration, which enables automation and high throughput applications. The current work provides a comparison of micro‐scale and direct immersion SPME (DI‐SPME) for screening of secondary metabolites, describes the optimization of the developed DI‐SPME method, and introduces the developed technique for mapping of target secondary metabolites as well as its direct coupling to mass spectrometry for such applications. The optimized DI‐SPME method provided higher amounts of extracted ions and intensity signals, yielding superior extraction and desorption efficiency as compared with micro‐scale extraction. Studied compounds presented stability on the coating for 24 h at room temperature. The DI‐SPME mapping approach revealed that lysolipin I and the lienomycin analog are distributed along the center and edges of the colony, respectively. Direct coupling of SPME to MS provided a similar ions profile as SPME‐LC‐MS while enabling a significant decrease in analysis time, demonstrating its suitability for such applications. DI‐SPME is herein presented as an alternative to micro‐scale extraction for screening of secondary metabolites in actinobacteria solid medium, as well as a feasible alternative to DESI‐IMS for mapping of biologic radial distribution of secondary metabolites and cell life cycle studies. Lastly, the direct coupling of DI‐SPME to MS is presented as a fast, powerful technique for high throughput analysis of secondary metabolites in this medium.

    更新日期:2019-12-09
  • Analysis of tetrahydrocannabinol derivative from cannabis‐infused chocolate by QuEChERS‐thin layer chromatography‐desorption electrospray ionization mass spectrometry
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-11-08
    Maryam Yousefi‐Taemeh, Demian R. Ifa

    Recently in Canada and some states of the United States, marijuana (cannabis) has become fully legalized and regulated, for both medical and recreational purposes. This fact is going to make cannabis products such as edibles even more popular than ever before. Therefore, it is assumed that there will be a high demand for analytical methods, which are accurate and sensitive enough to be used in different forensic and pharmaceutical cannabis–related applications. Cannabis derivatives have an extreme range and number of constituents with possible interactions with one another. Thus, this characteristic leads to their vast and highly complex chemistry, which requires robust analytical tools to be able to precisely and accurately quantify and qualify them. We developed and validated an analytical method using desorption electrospray ionization (DESI)–mass spectrometry (MS) to accurately detect, characterize, and quantify cannabinoids and also offer an easy, cost‐effective, and reliable technique, which can be performed in a short time for infused edibles in complex matrices such as chocolate. We evaluated a quantitative analysis of tetrahydrocannabinol (THC) in cannabis‐infused chocolate with thin‐layer chromatography (TLC)–DESI‐MS and QuEChERS extraction method. Both techniques of TLC and QuEChERS are cost‐effective and can be run in short time.

    更新日期:2019-12-09
  • Structural characterization of the ligstroside aglycone isoforms in virgin olive oils by liquid chromatography–high‐resolution Fourier‐transform mass spectrometry and H/Dexchange
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-11-08
    Ramona Abbattista, Ilario Losito, Cristina De Ceglie, Graziana Basile, Cosima D. Calvano, Francesco Palmisano, Tommaso R.I. Cataldi

    A systematic structural characterization of the isomeric forms related to ligstroside aglycone (LA), one of the most relevant secoiridoids contained in virgin olive oils, was performed using reverse phase liquid chromatography with electrospray ionization Fourier‐transform single and tandem mass spectrometry, operated in negative ion mode (RPLC‐ESI(−)‐FTMS and FTMS/MS). The high mass resolution and accuracy provided by the adopted orbital trap mass analyzer enabled the recognition of more than 10 different isomeric forms of LA in virgin olive oil extracts. They were related to four different types of molecular structure, two of which including a dihydropyranic ring bearing one or two aldehydic groups, whereas the others corresponded to dialdehydic open‐structure forms, differing just for the position of a C═C bond. The contemporary presence of enolic or dienolic tautomers associated to most of these compounds, stable at room temperature (23°C), was also assessed through RPLC‐ESI‐FTMS analyses operated under H/D exchange conditions, ie, by using D2O instead of H2O as co‐solvent of acetonitrile in the RPLC mobile phase. As discussed in the paper, the results obtained for LA indicated a remarkable structural similarity with oleuropein aglycone (OA), the most abundant secoiridoid of olive oil, whose isoforms had been previously characterized using the same analytical approach.

    更新日期:2019-12-09
  • MALDI imaging directed laser ablation tissue microsampling for data independent acquisition proteomics
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-05
    Kelin Wang, Fabrizio Donnarumma, Michael E. Pettit, Carson W. Szot, Touradj Solouki, Kermit K. Murray

    A multimodal workflow for mass spectrometry imaging was developed that combines MALDI imaging with protein identification and quantification by liquid chromatography tandem mass spectrometry (LC‐MS/MS). Thin tissue sections were analyzed by MALDI imaging, and the regions of interest (ROI) were identified using a smoothing and edge detection procedure. A midinfrared laser at 3‐μm wavelength was used to remove the ROI from the brain tissue section after MALDI mass spectrometry imaging (MALDI MSI). The captured material was processed using a single‐pot solid‐phase‐enhanced sample preparation (SP3) method and analyzed by LC‐MS/MS using ion mobility (IM) enhanced data independent acquisition (DIA) to identify and quantify proteins; more than 600 proteins were identified. Using a modified database that included isoform and the post‐translational modifications chain, loss of the initial methionine, and acetylation, 14 MALDI MSI peaks were identified. Comparison of the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of the identified proteins was achieved through an evolutionary relationships classification system.

    更新日期:2019-12-05
  • Correlation of molecular and morphologic effects of thermoembolization in a swine model using mass spectrometry imaging
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-05
    Chunxiao Guo, Dodge L. Baluya, Emily A. Thompson, Elizabeth M. Whitley, Erik N.K. Cressman

    Hepatocellular carcinoma is a growing worldwide problem with a high mortality rate. This malignancy does not respond well to chemotherapy, and most patients present late in their disease at which time surgery is no longer an option. Over the past three decades, minimally invasive methods have evolved to treat unresectable disease and prolong survival. Intra‐arterial embolization techniques are used for large or multiple tumors but have distressingly high levels of local recurrence and can be costly to implement. A new method called thermoembolization was recently reported, which destroys target tissue by combining reactive exothermic chemistry with an extreme local change in pH and ischemia. Described herein are experiments performed using this technique in vivo in a swine model. A microcatheter was advanced under fluoroscopic guidance into a branch of the hepatic artery to deliver a targeted dose of dichloroacetyl chloride dissolved in ethiodized oil into the liver. The following day, the animals were imaged by computed tomography and euthanized. Assessing the reaction product distribution and establishing a correlation with the effects are important for understanding the effects. This presented a significant challenge, however, as the reagent used does not contain a chromophore and is not otherwise readily detectable. Mass spectrometry imaging was employed to determine spatial distribution in treated samples. Additional insights on the biology were obtained by correlating the results with histology, immunohistochemistry, and immunofluorescence. The results are encouraging and may lead to a therapy with less local recurrence and improved overall survival for patients with this disease.

    更新日期:2019-12-05
  • MALDI imaging mass spectrometry of β‐ and γ‐crystallins in the ocular lens
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-05
    David M. Anderson, Mitchell G. Nye‐Wood, Kristie L. Rose, Paul J. Donaldson, Angus C. Grey, Kevin L. Schey

    Lens crystallin proteins make up 90% of expressed proteins in the ocular lens and are primarily responsible for maintaining lens transparency and establishing the gradient of refractive index necessary for proper focusing of images onto the retina. Age‐related modifications to lens crystallins have been linked to insolubilization and cataractogenesis in human lenses. Matrix‐assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) has been shown to provide spatial maps of such age‐related modifications. Previous work demonstrated that, under standard protein IMS conditions, α‐crystallin signals dominated the mass spectrum and age‐related modifications to α‐crystallins could be mapped. In the current study, a new sample preparation method was optimized to allow imaging of β‐ and γ‐crystallins in ocular lens tissue. Acquired images showed that γ‐crystallins were localized predominately in the lens nucleus whereas β‐crystallins were primarily localized to the lens cortex. Age‐related modifications such as truncation, acetylation, and carbamylation were identified and spatially mapped. Protein identifications were determined by top‐down proteomics analysis of lens proteins extracted from tissue sections and analyzed by LC‐MS/MS with electron transfer dissociation. This new sample preparation method combined with the standard method allows the major lens crystallins to be mapped by MALDI IMS.

    更新日期:2019-12-05
  • Visualizing the agreement of peptide assignments between different search engines
    J. Mass Spectrom. (IF 2.267) Pub Date : 2019-12-03
    Annelies Agten, Joris Van Houtven, Manor Askenazi, Tomasz Burzykowski, Kris Laukens, Dirk Valkenborg

    There is a trend in the analysis of shotgun proteomics data that aims to combine information from multiple search engines to increase the number of peptide annotations in an experiment. Typically, the degree of search engine complementarity and search engine agreement is visually illustrated by means of Venn diagrams that present the findings of a database search on the level of the nonredundant peptide annotations. We argue this practice to be not fit‐for‐purpose since the diagrams do not take into account and often conceal the information on complementarity and agreement at the level of the spectrum identification. We promote a new type of visualization that provides insight on the peptide sequence agreement at the level of the peptide‐spectrum match (PSM) as a measure of consensus between two search engines with nominal outcomes. We applied the visualizations and percentage sequence agreement to an in‐house data set of our benchmark organism, Caenorhabditis elegans, and illustrated that when assessing the agreement between search engine, one should disentangle the notion of PSM confidence and PSM identity. The visualizations presented in this manuscript provide a more informative assessment of pairs of search engines and are made available as an R function in the Supporting Information.

    更新日期:2019-12-03
Contents have been reproduced by permission of the publishers.
导出
全部期刊列表>>
2020新春特辑
限时免费阅读临床医学内容
ACS材料视界
科学报告最新纳米科学与技术研究
清华大学化学系段昊泓
自然科研论文编辑服务
中国科学院大学楚甲祥
上海纽约大学William Glover
中国科学院化学研究所
课题组网站
X-MOL
北京大学分子工程苏南研究院
华东师范大学分子机器及功能材料
中山大学化学工程与技术学院
试剂库存
天合科研
down
wechat
bug