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  • High resolution mass spectrometry for single cell analysis
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2020-01-21
    Muhammad Shemyal Nisar; Xiangwei Zhao
    更新日期:2020-01-21
  • 更新日期:2020-01-17
  • Electron attachment and electron ionization of helium droplets containing clusters of C60 and formic acid
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2020-01-16
    Masoomeh Mahmoodi-Darian; Elias Jabbour Al Maalouf; Samuel Zöttl; Paul Scheier; Olof Echt
    更新日期:2020-01-16
  • 更新日期:2020-01-13
  • 更新日期:2020-01-09
  • Design, construction and performance of a TOF-SIMS for analysis of trace elements in geological materials
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2020-01-02
    Tao Long; Stephen W.J. Clement; Hangqiang Xie; Dunyi Liu
    更新日期:2020-01-02
  • Comparative evaluation of two Fusarium oxysporum f. sp. lycopersici strains grown on two different carbon sources: LC-MS - based secretome study after in vivo 15N metabolic labeling
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2019-12-28
    Kazimierz Wrobel; Katarzyna Wrobel; Bianey Garcia Lara; Moises Guerrero Esperanza; Maria Isabel González Roncero; Alma Rosa Corrales Escobosa
    更新日期:2019-12-29
  • 更新日期:2019-12-25
  • Vacuum ultraviolet photoionization and ionic fragmentation of the isoxazole molecules
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2019-12-18
    Tomasz J. Wasowicz; Antti Kivimäki; Daniele Catone; Robert Richter
    更新日期:2019-12-19
  • Analytical determination of radioactive strontium and cesium by Thermal Ionization Mass Spectrometry
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2019-12-17
    M.P. Dion; Kellen W.E. Springer; Ryan I. Sumner; May-Lin P. Thomas; Gregory C. Eiden
    更新日期:2019-12-18
  • 更新日期:2019-12-02
  • Imaging of triglycerides in tissues using nanospray desorption electrospray ionization (Nano-DESI) mass spectrometry
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2019-11-27
    Daisy Unsihuay, Jiamin Qiu, Sneha Swaroop, Konstantin O. Nagornov, Anton N. Kozhinov, Yury O. Tsybin, Shihuan Kuang, Julia Laskin
    更新日期:2019-11-28
  • 更新日期:2019-11-28
  • Promoting carboxylate salts in the ESI source to simplify positive mode MS/MS sequencing of acid-terminated encoded polyurethanes
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2019-11-27
    Salomé Poyer, Benoit Eric Petit, Sofia Telitel, Denise Karamessini, Jean-François Lutz, Laurence Charles
    更新日期:2019-11-28
  • O- and N-glycosylation analysis of cell lines by ultrahigh resolution MALDI-FTICR-MS
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2019-11-26
    Gerda C.M. Vreeker, Simone Nicolardi, Katarina Madunic, Maximilianos Kotsias, Yuri E.M. van der Burgt, Manfred Wuhrer

    Glycosylation analysis from biological samples is often challenging due to the high complexity of the glycan structures found in these samples. In the present study N- and O- glycans from human colorectal cancer cell lines and human plasma were analyzed using ultrahigh resolution MALDI-FTICR-MS. N-glycans were enzymatically released from cell lines and plasma proteins, whereas beta-elimination was used for the release of O-glycans from the cells. The purified samples were mass analyzed using a 15T MALDI-FTICR-MS system, with additional MS/MS (collision-induced dissociation) experiments for O-glycan identifications. A total of 104 O-glycan and 62 N-glycan compositions were observed in the spectra obtained from colorectal cancer cell line samples. In the cell line N-glycan spectra, the highest intensity signals originated from high-mannose glycans, next to the presence of various complex type glycans. Notably, in the O-glycan spectra mono- and disaccharide signals were observed, which are difficult to detect using alternative glycomic platforms such as porous graphitized carbon LC-MS. In the N-glycan spectra from plasma, isobaric species were resolved in MALDI-FTICR-MS spectra using absorption mode whereas these overlapped in magnitude mode. The use of ultrahigh resolution MALDI-FTICR-MS for the analysis of glycans in complex mixtures enables us to confidently analyze glycans in the matrix region of the spectrum and to differentiate isobaric glycan species.

    更新日期:2019-11-27
  • Open search unveils modification patterns in formalin-fixed, paraffin-embedded thermo HCD and SCIEX TripleTOF shotgun proteomes
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2019-11-24
    David L. Tabb, Brandon D. Murugan, Javan Okendo, Omesan Nair, Jonathan M. Blackburn, Sindisiwe G. Buthelezi, Stoyan Stoychev

    The application of database search algorithms with very wide precursor mass tolerances for the “Open Search” paradigm has brought new efforts at post-translational modification discovery in shotgun proteomes. This approach has motivated the acceleration of database search tools by incorporating fragment indexing features. In this report, we compare open searches and sequence tag searches of high-resolution tandem mass spectra to seek a common “palette” of modifications when analyzing multiple formalin-fixed, paraffin-embedded (FFPE) tissues from Thermo Q-Exactive and SCIEX TripleTOF instruments. While open search in MSFragger produced some gains in identified spectra, careful FDR control limited the best result to 24% more spectra than narrow search (worst result: a loss of 9%). Open pFind produced high apparent sensitivity for PSMs, but entrapment sequences hinted that the actual error rate may be higher than reported by the software. Combining sequence tagging, open search, and chemical knowledge, we converged on this set of PTMs for our four FFPE sets: mono- and di-methylation (nTerm and Lys), single and double oxidation (Met and Pro), and variable carbamidomethylation (nTerm and Cys).

    更新日期:2019-11-26
  • Chromatographic purification of Ca and Mg from biological and geological samples for isotope analysis by MC-ICP-MS
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2019-11-23
    Zhian Bao, Chunlei Zong, Kaiyun Chen, Nan Lv, Honglin Yuan

    This study presented a chemical protocol for purification of calcium and magnesium from a single aliquot of biological and geological samples. The separation protocol was based on a two-step cation exchange chromatography using DGA resin and AG50W-X12 (200–400 mesh) resin. Calcium fraction was first collected using 0.25 mL of DGA resin, and Mg fraction was then collected using 0.5 mL of AG50W-X12 cation exchange resin. For Ca isotope analysis, the effect of acidity and concentration mismatch as well as the matrix effect were rigorously evaluated using the Neptune Plus MC-ICP-MS with a wet-plasma mode. Based on repeated measurements on BHVO-2 and NIST SRM 1400, the long-term reproducibility was evaluated at 0.08‰ (2SD) for δ44/42Ca915a. The δ26Mg ratios of the analyzed reference materials varied from -1.22‰ to 0.03‰ with the external precision better than 0.11‰ (2SD). The robustness of the protocol has been validated by replicated analyses of biological and geological standards. Calcium and magnesium isotopic ratios of all reference materials measured in this study agreed well with previous data within uncertainties. Therefore, the proposed method can be used for simultaneous determination of Ca and Mg isotopic ratios from a single aliquot of biological and geological samples.

    更新日期:2019-11-26
  • Power series expansion of axially symmetric toroidal harmonics for toroidal ion trap
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2019-11-21
    Appala Naidu Kotana, Atanu K. Mohanty
    更新日期:2019-11-21
  • A novel method for producing NH4+ reagent ions in the hollow cathode glow discharge ion source of PTR-MS instruments
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2019-11-09
    Markus Müller, Felix Piel, Rene Gutmann, Philipp Sulzer, Eugen Hartungen, Armin Wisthaler
    更新日期:2019-11-11
  • Ablation of tungsten surfaces in collisions with Ar+, He+ and N2+ cation projectiles in the presence of D2
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2019-11-06
    Lorenz Ballauf, Faro Hechenberger, Diethard K. Bohme, Paul Scheier
    更新日期:2019-11-07
  • 更新日期:2019-11-06
  • Rapid screening and identification of targeted or non-targeted antitussive adulterants in herbal medicines by Q-Orbitrap HRMS and screening database
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2019-11-01
    Changchuan Guo, Liping Gong, Weijian Wang, Jiawei Leng, Liming Zhou, Sheng Xing, Yanxia Zhao, Ruiqing Xian, Xunjie Zhang, Feng Shi
    更新日期:2019-11-01
  • Intrinsic Size Parameters for Palmitoylated and Carboxyamidomethylated Peptides.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2015-05-30
    Zhiyu Li,Jonathan M Dilger,Vikas Pejaver,David Smiley,Randy J Arnold,Sean D Mooney,Suchetana Mukhopadhyay,Predrag Radivojac,David E Clemmer

    Cross sections for 61 palmitoylated peptides and 73 cysteine-unmodified peptides are determined and used together with a previously obtained tryptic peptide library to derive a set of intrinsic size parameters (ISPs) for the palmitoyl (Pal) group (1.26 ± 0.04), carboxyamidomethyl (Am) group (0.92 ± 0.04), and the 20 amino acid residues to assess the influence of Pal- and Am-modification on cysteine and other amino acid residues. These values highlight the influence of the intrinsic hydrophobic and hydrophilic nature of these modifications on the overall cross sections. As a part of this analysis, we find that ISPs derived from a database of a modifier on one amino acid residue (CysPal) can be applied on the same modification group on different amino acid residues (SerPal and TyrPal). Using these ISP values, we are able to calculate peptide cross sections to within ± 2% of experimental values for 83% of Pal-modified peptide ions and 63% of Am-modified peptide ions. We propose that modification groups should be treated as individual contribution factors, instead of treating the combination of the particular group and the amino acid residue they are on as a whole when considering their effects on the peptide ion mobility features.

    更新日期:2019-11-01
  • Surface induced dissociation yields substructure of Methanosarcina thermophila 20S proteasome complexes.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2015-05-26
    Xin Ma,Joseph A Loo,Vicki H Wysocki

    Native mass spectrometry (MS) and surface induced dissociation (SID) have been applied to study the stoichiometry and quaternary structure of non-covalent protein complexes. In this study, Methanosarcina thermophila 20S proteasome, which consists of four stacked heptameric rings (α7β7β7α7 symmetry), has been selected to explore the SID dissociation pattern of a complicated stacked ring protein complex. SID produces both α and β subunits while collision induced dissociation (CID) produces only highly charged α subunit. In addition, the charge reduced 20S proteasome produces the α7β7 fragment, reflecting the stacked ring topology of the complex. The combination of SID and charge reduction is shown to be a powerful tool for the study of protein complex structure.

    更新日期:2019-11-01
  • Signal and Charge Enhancement for Protein Analysis by Liquid Chromatography-Mass Spectrometry with Desorption Electrospray Ionization.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2012-07-01
    Yan Liu,Zhixin Miao,Rajeswari Lakshmanan,Rachel R Ogorzalek Loo,Joseph A Loo,Hao Chen

    We recently reported the use of desorption electrospray ionization (DESI) as a novel interface to couple high-performance liquid chromatography (HPLC) with mass spectrometry (MS) (Chem. Commun. 2011, 47, 4171). One of the benefits of such an interface is that post-column derivatization of separated analytes can be integrated with ionization via a "reactive" DESI approach in which a derivatizing reagent is doped into the spray solvent. The reactive DESI interface allows analyte desorption/ionization from the end of the chromatographic column with prompt MS detection; a short time delay of ~20 ms was demonstrated. In this study, we extended this application by "supercharging" proteins following HPLC separation using a DESI spray solvent containing supercharging reagents, m-nitrobenzyl alcohol (m-NBA) or sulfolane. Proteins (insulin, ubiquitin, lysozyme and α-lactalbumin) eluted out of the LC column can be supercharged with the protein charge state distributions (CSDs) significantly increased (to higher charge), which would be advantageous for subsequent top-down MS analysis of proteins. Interestingly, supercharging combined with reactive DESI enhances tolerance towards trifluoroacetic acid (TFA), which is known to be a superior additive in the mobile phase for premium peptide/protein chromatographic separation but has severe signal suppression effects for conventional electrospray ionization (ESI). In comparison to electrosonic spray ionization (ESSI), a variant form of ESI, the sensitivity of protein analysis using LC/DESI-MS with the mobile phase containing TFA can be improved by up to 70-fold for lysozyme and α-lactalbumin by including m-NBA in the DESI spray solvent. Presumably, by reducing TFA dissociation in the droplet, supercharging agents lower trifluoroacetate anion concentrations and concomitantly reduce ion pairing to analyte cationic sites. The reduced ion pairing therefore decreases the TFA signal suppression effect. The supercharging capability and the reduction of TFA signal suppression suggest that LC/DESI-MS is a valuable method for protein analysis.

    更新日期:2019-11-01
  • Cation-Dependent Conformations in 25-Hydroxyvitamin D3-Cation Adducts Measured by Ion Mobility-Mass Spectrometry and Theoretical Modeling.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2018-07-24
    Christopher D Chouinard,Vinicius Wilian D Cruzeiro,Robin H J Kemperman,Nicholas R Oranzi,Adrian E Roitberg,Richard A Yost

    Ion mobility-mass spectrometry is a useful tool in separation of biological isomers, including clinically relevant analytes such as 25-hydroxyvitamin D3 (25OHD3) and its epimer, 3-epi-25-hydroxyvitamin D3 (epi25OHD3). Previous research indicates that these epimers adopt different gas-phase sodiated monomer structures, either the "open" or "closed" conformer, which allow 25OHD3 to be readily resolved in mixtures. In the current work, alternative metal cation adducts are investigated for their relative effects on the ratio of "open" and "closed conformers. Alkali and alkaline earth metal adducts caused changes in the 25OHD3 conformer ratio, where the proportion of the "open" conformer generally increases with the size of the metal cation in a given group. As such, the ratio of the "open" conformer, which is unique to 25OHD3 and absent for its epimer, can be increased from approximately 1:1 for the sodiated monomer to greater than 8:1 for the barium adduct. Molecular modeling and energy calculations agree with the experimental results, indicating that the Gibbs free energy of conversion from the "closed" to the "open" conformation decreased with increasing cation size, correlating with the variation in ratio between the conformers. This work demonstrates the effect of cation adducts on gas-phase conformations of small, flexible molecules and offers an additional strategy for resolution of clinically relevant epimers.

    更新日期:2019-11-01
  • Oxidative Post-Translational Modifications of an Amyloidogenic Immunoglobulin Light Chain Protein.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2018-01-24
    Yanyan Lu,Yan Jiang,Tatiana Prokaeva,Lawreen H Connors,Catherine E Costello

    Immunoglobulin light chain amyloidosis (AL) is a plasma cell disorder characterized by overproduction and deposition of monoclonal immunoglobulin (Ig) light chains (LC) or variable region fragments as amyloid fibrils in various organs and tissues. Much clinical evidence indicates that patients with AL amyloidosis sustain cardiomyocyte impairment and suffer from oxidative stress. We seek to understand the underlying biochemical pathways whose disruption or amplification during sporadic or sustained disease states leads to harmful physiological consequences and to determine the detailed structures of intermediates and products that serve as signposts for the biochemical changes and represent potential biomarkers. In this study, matrix-assisted laser desorption/ionization mass spectrometry provided extensive evidence for oxidative post-translational modifications (PTMs) of an amyloidogenic Ig LC protein from a patient with AL amyloidosis. Some of the tyrosine residues were heavily mono- or di-chlorinated. In addition, a novel oxidative conversion to a nitrile moiety was observed for many of the terminal aminomethyl groups on lysine side chains. In vitro experiments using model peptides, in-solution oxidation, and click chemistry demonstrated that hypochlorous acid produced by the myeloperoxidase - hydrogen peroxide - chloride system could be responsible for these and other, more commonly observed modifications.

    更新日期:2019-11-01
  • CD34 Antigen: Determination of Specific Sites of Phosphorylation In Vitro and In Vivo.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2011-04-19
    Leesa J Deterding,Jason G Williams,Margaret M Humble,Robert M Petrovich,Sung-Jen Wei,Carol S Trempus,Matthew B Gates,Feng Zhu,Robert C Smart,Raymond W Tennant,Kenneth B Tomer

    CD34, a type I transmembrane glycoprotein, is a surface antigen which is expressed on several cell types, including hematopoietic progenitors, endothelial cells, as well as mast cells. Recently, CD34 has been described as a marker for epidermal stem cells in mouse hair follicles, and is expressed in outer root sheath cells of the human hair follicle. Although the biological function and regulation of CD34 is not well understood, it is thought to be involved in cell adhesion as well as possibly having a role in signal transduction. In addition, CD34 was shown to be critical for skin tumor development in mice, although the exact mechanism remains unknown.Many proteins' functions and biological activities are regulated through post-translational modifications. The extracellular domain of CD34 is heavily glycosylated but the role of these glycans in CD34 function is unknown. Additionally, two sites of tyrosine phosphorylation have been reported on human CD34 and it is known that CD34 is phosphorylated, at least in part, by protein kinase C; however, the precise location of the sites of phosphorylation has not been reported. In an effort to identify specific phosphorylation sites in CD34 and delineate the possible role of protein kinase C, we undertook the identification of the in vitro sites of phosphorylation on the intracellular domain of mouse CD34 (aa 309-382) following PKC treatment. For this work, we are using a combination of enzymatic proteolysis and peptide sequencing by mass spectrometry. After which the in vivo sites of phosphorylation of full-length mouse CD34 expressed from HEK293F cells were determined. The observed in vivo sites of phosphorylation, however, are not consensus PKC sites, but our data indicate that one of these sites may possibly be phosphorylated by AKT2. These results suggest that other kinases, as well as PKC, may have important signaling functions in CD34.

    更新日期:2019-11-01
  • A Minimalist Approach to MALDI Imaging of Glycerophospholipids and Sphingolipids in Rat Brain Sections.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2009-12-04
    Hay-Yan J Wang,Shelley N Jackson,Jeremy Post,Amina S Woods

    Matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a powerful tool that has allowed researchers to directly probe tissue molecular structure and drug content with minimal manipulations, while maintaining anatomical integrity. In the present work glycerophospholipids and sphingolipids images were acquired from 16 µm thick coronal rat brain sections using MALDI-MS. Images of phosphatidylinositol 38:4 (PI 38:4), suifatide 24:1 (ST 24:1), and hydroxyl sulfatide 24:1 (ST 24:1 (OH)) were acquired in negative ion mode, while the images of phosphatidylcholine 34:1 (PC 34:1), potassiated phosphatidylcholines 32:0 (PC32:0 + K(+)) and 36:1 (PC 36:1 +K(+)) were acquired in positive ion mode. The images of PI 38:4 and PC 36:1+K(+) show the preferential distribution of these two lipids in gray matter; and the images of two sulfatides and PC 32:0+K(+) show their preferential distribution in white matter. In addition, the gray cortical band and its adjacent anatomical structures were also identified by contrasting their lipid makeup. The resulting images were compared to lipid images acquired by secondary ion mass spectrometry (SIMS). The suitability of TLC sprayers, Collison Nebulizer, and artistic airbrush were also evaluated as means for matrix deposition.

    更新日期:2019-11-01
  • Ion-Ion Reactions with Fixed-Charge Modified Proteins to Produce Ions in a Single, Very High Charge State.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2009-10-06
    Brian L Frey,Casey J Krusemark,Aaron R Ledvina,Joshua J Coon,Peter J Belshaw,Lloyd M Smith

    Electrospray ionization (ESI) of denatured proteins produces a mass spectrum with a broad distribution of multiply charged ions. Attaching fixed positive charges, specifically quaternary ammonium groups, to proteins at their carboxylic acid groups generates substantially higher charge states compared to the corresponding unmodified proteins in positive-mode ESI. Ion-ion reactions of these modified proteins with reagent anions leads to charge reduction by proton transfer. These proton transfer reactions cannot remove charge from the quaternary ammonium groups, which do not have a proton to transfer to the anion. Thus, one might expect charge reduction to stop at a single charge state equal to the number of fixed charges on the modified protein. However, ion-ion reactions yield charge states lower than this number of fixed charges due to anion attachment (adduction) to the proteins. Charge reduction via ion-molecule reactions involving gas-phase bases also give adducts on the modified protein ions in low charge states. Such adducts are avoided by keeping the ions in charge states well above the number of fixed charges. In the present work protein ions were selectively "parked" within an ion trap mass spectrometer in a high charge state by mild radiofrequency excitation that dramatically slows their ion-ion reaction rate-a technique termed "ion parking". The combination of ion parking with the fixed-charge modified proteins permits generation of a large population of ions in a single, very high charge state.

    更新日期:2019-11-01
  • Characterization of applied fields for ion mobility separations in traveling wave based structures for lossless ion manipulations (SLIM).
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2019-08-31
    Ahmed M Hamid,Aneesh Prabhakaran,Sandilya V B Garimella,Yehia M Ibrahim,Richard D Smith

    Ion mobility (IM) is rapidly gaining attention for the separation and analysis of biomolecules due to the ability to distinguish the shapes of ions. However, conventional constant electric field drift tube IM separations have limited resolving power, constrained by practical limitations on the path length and maximum applied voltage. The implementation of traveling waves (TW) in IM removes the latter limitation, allowing higher resolution to be achieved using extended path lengths. Both of these can be readily obtained in structures for lossless ion manipulations (SLIM), which are fabricated from arrays of electrodes patterned on two parallel surfaces where potentials are applied to generate appropriate electric fields between the surfaces. Here we have investigated the relationship between the primary SLIM variables, such as electrode dimensions, inter-surface gap, and the applied TW voltages, that directly impact the fields experienced by ions. Ion trajectory simulations and theoretical calculations have been utilized to understand the dependence of SLIM geometry and effective electric fields on IM resolution. The variables explored impact both ion confinement and the observed IM resolution using SLIM modules.

    更新日期:2019-11-01
  • A Review of Tandem Mass Spectrometry Characterization of Adenosine Diphosphate-Ribosylated Peptides.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2012-05-09
    Shawna M Hengel,David R Goodlett

    The use of tandem mass spectrometry to identify and characterize sites of protein adenosine diphosphate (ADP) ribosylation will be reviewed. Specifically, we will focus on data acquisition schemes and fragmentation techniques that provide peptide sequence and modification site information. Also discussed are uses of synthetic standards to aid characterization, and an enzymatic method that converts ADP-ribosylated peptides into ribosyl mono phosphorylated peptides making identification amenable to traditional phosphopeptide characterization methods. Finally the potential uses of these techniques to characterize poly ADP-ribosylation sites, and inherent challenges, are addressed.

    更新日期:2019-11-01
  • Subnanogram proteomics: impact of LC column selection, MS instrumentation and data analysis strategy on proteome coverage for trace samples.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2018-03-27
    Ying Zhu,Rui Zhao,Paul D Piehowski,Ronald J Moore,Sujung Lim,Victoria J Orphan,Ljiljana Paša-Tolić,Wei-Jun Qian,Richard D Smith,Ryan T Kelly

    One of the greatest challenges for mass spectrometry (MS)-based proteomics is the limited ability to analyze small samples. Here we investigate the relative contributions of liquid chromatography (LC), MS instrumentation and data analysis methods with the aim of improving proteome coverage for sample sizes ranging from 0.5 ng to 50 ng. We show that the LC separations utilizing 30-μm-i.d. columns increase signal intensity by >3-fold relative to those using 75-μm-i.d. columns, leading to 32% increase in peptide identifications. The Orbitrap Fusion Lumos MS significantly boosted both sensitivity and sequencing speed relative to earlier generation Orbitraps (e.g., LTQ-Orbitrap), leading to a ~3-fold increase in peptide identifications and 1.7-fold increase in identified protein groups for 2 ng tryptic digests of the bacterium S. oneidensis. The Match Between Runs algorithm of open-source MaxQuant software further increased proteome coverage by ~ 95% for 0.5 ng samples and by ~42% for 2 ng samples. Using the best combination of the above variables, we were able to identify >3,000 proteins from 10 ng tryptic digests from both HeLa and THP-1 mammalian cell lines. We also identified >950 proteins from subnanogram archaeal/bacterial cocultures. The present ultrasensitive LC-MS platform achieves a level of proteome coverage not previously realized for ultra-small sample loadings, and is expected to facilitate the analysis of subnanogram samples, including single mammalian cells.

    更新日期:2019-11-01
  • Portable FAIMS: Applications and Future Perspectives.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2018-01-18
    Michael T Costanzo,Jared J Boock,Robin H J Kemperman,Michael S Wei,Christopher R Beekman,Richard A Yost

    Miniaturized mass spectrometry (MMS) is optimal for a wide variety of applications that benefit from field-portable instrumentation. Like MMS, field asymmetric ion mobility spectrometry (FAIMS) has proven capable of providing in situ analysis, allowing researchers to bring the lab to the sample. FAIMS compliments MMS very well, but has the added benefit of operating at atmospheric pressure, unlike MS. This distinct advantage makes FAIMS uniquely suited for portability. Since its inception, FAIMS has been envisioned as a field-portable device, as it affords less expense and greater simplicity than many similar methods. Ideally, these are simple, robust devices that may be operated by non-professional personnel, yet still provide adequate data when in the field. While reducing the size and complexity tends to bring with it a loss of performance and accuracy, this is made up for by the incredibly high throughput and overall convenience of the instrument. Moreover, the FAIMS device used in the field can be brought back to the lab, and coupled to a conventional mass spectrometer to provide any necessary method development and compound validation. This work discusses the various considerations, uses, and applications for portable FAIMS instrumentation, and how the future of each applicable field may benefit from the development and acceptance of such a device.

    更新日期:2019-11-01
  • Quantitative imaging of deuterated metabolic tracers in biological tissues with nanoscale secondary ion mass spectrometry.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2017-12-26
    Christelle Guillermier,J Collin Poczatek,Walter R Taylor,Matthew L Steinhauser

    In the field of secondary ion mass spectrometry at nanometer scale (NanoSIMS), configuration of parallel detectors to routinely measure isotope ratios in sub-100 nm domains brings classical stable isotope tracer studies from the whole tissue level down to the suborganelle level. Over the past decade, the marriage of stable isotope tracers with NanoSIMS has been applied to a range of fundamental biological questions that were largely inaccessible by other means. Although multiplexed measurement of different stable isotope tracers is feasible, in practice there remains a gap in the current analytical capacity to efficiently measure stable isotopes commonly utilized in tracer studies. One such example is the measurement of deuterated tracers. The most obvious approach to measuring deuterium/hydrogen isotope ratios is at mass 2/1. However, the radius of the magnetic sector limits concomitant measurement of other masses critical to multiplexed exploration of biological samples. Here we determine the experimental parameters to measure deuterated tracers in biological samples using the C2H- polyatomic ion species (C2D-/C2H-) while operating the NanoSIMS at a reduced Mass Resolving Power of 14,000. Through control of the sputtering parameters, we demonstrate that there is an analytical window during which the C2D-/C2H- isotope ratio can be measured with sufficient precision for biological studies where the degree of D-labeling is typically well above natural abundance. We provide validation of this method by comparing the C2D measurement of D-water labeling in the murine small intestine relative to measurements of native D/H conducted in the same analytical fields. Additional proof-of-concept demonstrations include measurement of D-water, D-glucose, and D-thymidine in biological specimens. Therefore, this study provides a practical template for deuterium-based tracer studies in biological systems.

    更新日期:2019-11-01
  • Single Particle Analyzer of Mass: A Charge Detection Mass Spectrometer with a Multi-Detector Electrostatic Ion Trap.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2017-11-14
    Andrew G Elliott,Samuel I Merenbloom,Satrajit Chakrabarty,Evan R Williams

    A new charge detection mass spectrometer that combines array detection and electrostatic ion trapping to repeatedly measure the masses of single ions is described. This instrument has four detector tubes inside an electrostatic ion trap with conical electrodes (cone trap) to provide multiple measurements of an ion on each pass through the trap resulting in a signal gain over a conventional trap with a single detection tube. Simulations of a cone trap and a dual ion mirror trap design indicate that more passes through the trap per unit time are possible with the latter. However, the cone trap has the advantages that ions entering up to 2 mm off the central axis of the trap are still trapped, the trapping time is less sensitive to the background pressure, and only a narrow range of energies are trapped so it can be used for energy selection. The capability of this instrument to obtain information about the molecular weight distributions of heterogeneous high molecular weight samples is demonstrated with 8 MDa polyethylene glycol (PEG) and 50 and 100 nm amine modified polystyrene nanoparticle samples. The measured mass distribution of the PEG sample is centered at 8 MDa. The size distribution obtained from mass measurements of the 100 nm nanoparticle sample is similar to the size distribution obtained from transmission electron microscopy (TEM) images, but most of the smaller nanoparticles observed in TEM images of the 50 nm nanoparticles do not reach a sufficiently high charge to trigger the trap on a single pass and be detected by the mass spectrometer. With the maximum trapping time set to 100 ms, the charge uncertainty is as low as ±2 charges and the mass uncertainty is approximately 2% for PEG and polystyrene ions.

    更新日期:2019-11-01
  • 1,2,3,4,6-penta-O-galloyl-β-D-glucopyranose Binds to the N-terminal Metal Binding Region to Inhibit Amyloid β-protein Oligomer and Fibril Formation.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2017-10-24
    Natália E C de Almeida,Thanh D Do,Nichole E LaPointe,Michael Tro,Stuart C Feinstein,Joan-Emma Shea,Michael T Bowers

    The early oligomerization of amyloid β-protein (Aβ) is a crucial step in the etiology of Alzheimer's disease (AD), in which soluble and highly neurotoxic oligomers are produced and accumulated inside neurons. In search of therapeutic solutions for AD treatment and prevention, potent inhibitors that remodel Aβ assembly and prevent neurotoxic oligomer formation offer a promising approach. In particular, several polyphenolic compounds have shown anti-aggregation properties and good efficacy on inhibiting oligomeric amyloid formation. 1,2,3,4,6-penta-O-galloyl-β-D-glucopyranose is a large polyphenol that has been shown to be effective at inhibiting aggregation of full-length Aβ1-40 and Aβ1-42, but has the opposite effect on the C-terminal fragment Aβ25-35. Here, we use a combination of ion mobility coupled to mass spectrometry (IMS-MS), transmission electron microscopy (TEM) and molecular dynamics (MD) simulations to elucidate the inhibitory effect of PGG on aggregation of full-length Aβ1-40 and Aβ1-42. We show that PGG interacts strongly with these two peptides, especially in their N-terminal metal binding regions, and suppresses the formation of Aβ1-40 tetramer and Aβ1-42 dodecamer. By exploring multiple facets of polyphenol-amyloid interactions, we provide a molecular basis for the opposing effects of PGG on full-length Aβ and its C-terminal fragments.

    更新日期:2019-11-01
  • Gas-Phase Protein Salt Bridge Stabilities from Collisional Activation and Electron Transfer Dissociation.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2017-10-24
    Zhe Zhang,Richard W Vachet

    The gas phase structures of several proteins have been studied by electron transfer dissociation (ETD) with and without prior collisional heating after electrospraying these proteins from native-like solutions into a quadrupole ion trap mass spectrometer. Without prior collisional heating, we find that ETD fragmentation is mostly limited to regions of the protein that are not spanned by the salt bridges known to form in solution. When protein ions are collisionally heated before ETD, new product ions are observed, and in almost all cases, these new ions arise from protein regions that are spanned by the salt bridges. Together these results confirm the existence of salt bridges in protein ions and demonstrate that a sufficient amount energy is required to disrupt these salt bridges in the gas phase. More interestingly, we also show that different salt bridges require different collisional activation voltages to be disrupted, suggesting that they have variable stabilities in the gas phase. These stabilities appear to be influenced by the gas-phase basicities of the involved residues and the presence of nearby charged residues. We also find that higher collisional activation voltages are needed to enable the formation of new product from sites spanned by multiple salt bridges.

    更新日期:2019-11-01
  • Understanding Curli Amyloid-Protein Aggregation by Hydrogen-Deuterium Exchange and Mass Spectrometry.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2017-10-24
    Hanliu Wang,Qin Shu,Don L Rempel,Carl Frieden,Michael L Gross

    Bacteria within Curli biofilms are protected from environmental pressures (e.g., disinfectants, antibiotics), and this is responsible for intractable infections. Understanding aggregation of the major protein component of Curli, CsgA, may uncover disease-associated amyloidogenesis mechanisms. Here, we report the application of pulsed hydrogen-deuterium exchange and mass spectrometry (HDX-MS) to study CsgA aggregation, thereby obtaining region-specific information. By following time-dependent peptide signal depletion, presumably a result of insoluble fibril formation, we acquired sigmoidal profiles that are specific for regions (region-specific) of the protein. These signal-depletion profiles not only provide an alternative aggregation measurement, but also give insight on soluble species in the aggregation. The HDX data present as bimodal isotopic distributions, one representing a highly disordered species whereas the other a well-structured one. Although the extents of deuterium uptake of the two species remain the same with time, the relative abundance of the lower mass, less-exchanged species increases in a region-specific manner. The same region-specific aggregation properties also pertain to different aggregation conditions. Although CsgA is an intrinsically disordered protein, within the fibril it is thought to consist of five imperfect β-strand repeating units (labeled R1-R5). We found that the exterior repeating units R1 and R5 have higher aggregation propensities than do the interior units R2, R3, and R4. We also employed TEM to obtain complementary information of the well-structured species. The results provide insight on aggregation and a new approach for further application of HDX-MS to unravel aggregation mechanisms of amyloid proteins.

    更新日期:2019-11-01
  • Ion Mobility-Mass Spectrometry Reveals Evidence of Specific Complex Formation between Human Histone Deacetylase 8 and Poly-r(C)-binding Protein 1.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2017-10-07
    Shuai Niu,Byung Chul Kim,Carol A Fierke,Brandon T Ruotolo

    Histone deacetylase 8, part of a broad class of proteins responsible for regulating transcription and many other cellular processes and directly linked to a host of human disease through its mis-function, has been canonically described as a zinc-based mettalo-enzyme for many years. Recent evidence, however, has linked this protein to iron incorporation, loaded through transient interactions with the poly r(C)-binding protein 1, a metallo-chaperone and storage protein. In this report, we construct and deploy an electrospray-mass spectrometry based assay aimed at quantifying the interaction strength between these two weakly-associated proteins, as well as the zinc and iron associated form of the histone deacetylase. Despite challenges derived from artifact protein complexes derived from the electrospray process, we use carefully-constructed positive and negative control experiments, along with detailed measurements of protein ionization efficiency to validate our dissociation constant measurements for protein dimers in this size range. Furthermore, our data strongly support that complexes between histone deacetylase 8 and poly r(C)-binding protein 1 are specific, and that they are equally strong when both zinc and iron-loaded proteins are involved, or perhaps mildly promoted in the latter case, suggesting an in vivo role for the non-canonical, iron-incorporated histone deacetylase.

    更新日期:2019-11-01
  • Effects of ESI conditions on kinetic trapping of the solution-phase protonation isomer of p-aminobenzoic acid in the gas phase.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2017-08-07
    Amanda L Patrick,Adam P Cismesia,Larry F Tesler,Nicolas C Polfer

    The effects of electrospray ionization (ESI) solvent and source temperature on the relative abundance of the preferred solution-phase (N-protonated; i.e. amine) versus preferred gas-phase (O-protonated; i.e., acid) isomers of p-aminobenzoic acid (PABA) were investigated. When PABA was electrosprayed from protic solvents (i.e., methanol/water), the infrared multiple photon dissociation (IRMPD) spectrum recorded was consistent with that for O-protonation, according to both calculations and previous studies. When aprotic solvent (i.e., acetonitrile) was used, a different spectrum was recorded and was assigned to the N-protonated isomer. As the amine is the preferred protonation site in solution, this suggests that an isomerization takes place under certain conditions. Photodissociation at the diagnostic band for the O-protonated isomer (NH2 stretching mode) was used to quantify the relative contributions of each isomer to ion signal as a function of ESI conditions. For mixtures of methanol and acetonitrile, the relative contribution of the O-protonated gas-phase structure increased as a function of methanol content. Yet, substituting methanol for water resulted in a marked decrease of isomerization to the O-protonated structure. The source temperature (i.e., temperature of a heated desolvation capillary) was found to play a key role in determining the extent of isomerization, with higher temperatures yielding increased presence of gas-phase structures. These results are consistent with a protic bridge mechanism, in which the ESI droplet temperatures, dependent on endothermic desolvation and radiative heating from the capillary, may determine the isomerization yield.

    更新日期:2019-11-01
  • Protonated N-Alkyl-2-nitroanilines Undergo Intramolecular Oxidation of the Alkyl Chain upon Collisional Activation.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2017-02-01
    Justin Paulose,June Cyriac,George Mathai,Daryl Giblin,Michael L Gross

    The collisional activation of protonated N-propyl-2-nitroaniline obtained by electrospray ionization shows two major competitive dissociation pathways: the elimination of the elements of propionic acid, [M + H - C3H6O2]+ to give an m/z 107 ion, and of the elements of ethanol, [M + H - C2H6O]+ to give an m/z 135 ion. The mechanistic study reported here addresses these unusual fragmentations to reveal that both occur via a common intermediate formed by the transfer of an oxygen atom from the nitro group to the first carbon atom of the propyl group, allowing elimination of propionic acid and (H2O + ethene), respectively. The corresponding loss of CH4O does not occur when the propyl group is replaced by an ethyl group, but elimination of the elements of propanol does occur when propyl is replaced by a butyl group. Further, the product ions of m/z 107 and 135 are also formed when the propyl chain is replaced with a hexyl group.

    更新日期:2019-11-01
  • Molecular Characterization of Myelin Protein Zero in Xenopus laevis Peripheral Nerve: Equilibrium between Non-covalently Associated Dimer and Monomer.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2007-12-01
    Bo Xie,Xiaoyang Luo,Cheng Zhao,Christina Marie Priest,Shiu-Yung Chan,Peter B O' Connor,Daniel A Kirschner,Catherine E Costello

    Myelin protein zero (P0), a glycosylated single-pass transmembrane protein, is essential in the formation and maintenance of peripheral nervous system (PNS) compact myelin. P0 in Xenopus (xP0) exists primarily as a dimeric form that remains stable after various physical and chemical treatments. In exploring the nature of the interactions underlying the dimer stability, we found that xP0 dimer dissociated into monomer during continuous elution gel electrophoresis and conventional SDS-PAGE, indicating that the dimer is stabilized by non-covalent interactions. Furthermore, as some of the gel-purified monomer re-associated into dimer on SDS-PAGE gels, there is likely a dynamic equilibrium between xP0 dimer and monomer in vivo. Because the carbohydrate and fatty acyl moieties may be crucial for the adhesion role of P0, we used sensitive mass spectrometry approaches to elucidate the detailed N-glycosylation and S-acylation profiles of xP0. Asn92 was determined to be the single, fully-occupied glycosylation site of xP0, and a total of 12 glycans was detected that exhibited new structural features compared with those observed from P0 in other species: (1) the neutral glycans were composed mainly of high mannose and hybrid types; (2) five of twelve were acidic glycans, among which three were sialylated and the other two were sulfated; (3) none of the glycans had core fucosylation; and (4) no glucuronic acid, hence no HNK-1 epitope, was detected. The drastically different carbohydrate structures observed here support the concept of the species-specific variation in N-glycosylation of P0. Cys152 was found to be acylated with stearoyl (C18:0), whereas palmitoyl (C16:0) is the corresponding predominant fatty acyl group on P0 from higher vertebrates. We propose that the unique glycosylation and acylation patterns of Xenopus P0 may underlie its unusual dimerization behaviour. Our results should shed light on the understanding of the phylogenetic development of P0's adhesion role in PNS compact myelin.

    更新日期:2019-11-01
  • Top-Down Protein Identification using a Time-of-Flight Mass Spectrometer and Data Independent Acquisition.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2019-05-21
    Rajeswari Lakshmanan,Joseph A Loo

    Top-down mass spectrometry and direct dissociation of gas phase intact proteins have been demonstrated to be a powerful platform for identifying proteins from complex mixtures and for elucidating post-translational modifications (PTMs). Fragmentation of proteins in the atmospheric pressure/vacuum interface of the electrospray ionization mass spectrometer is an effective dissociation technique that can be utilized for on-line HPLC top-down analysis. We demonstrate the capability to perform intact protein identifications in a single-stage time-of- flight (TOF) mass spectrometer in a data independent (DIA) acquisition fashion by rapidly switching the in-source dissociation (ISD) energy during protein elution from a liquid chromatography (LC) column. The intact protein and product ion masses obtained at low and high ISD energies, respectively, were measured using a TOF mass analyzer. By coupling on-line protein separations to dissociation in the atmospheric pressure/vacuum interface region of the mass spectrometer, we identified proteins in simple complexity mixtures, including subunits from the human 20S proteasome complex, and PTMs such as phosphorylation and N-terminal acetylation events. This proof-of-principle study demonstrates that a data-independent pseudo- MS/MS method could be a relatively in-expensive platform for top-down MS.

    更新日期:2019-11-01
  • Mass spectrometric analysis of the N-glycoproteome in statin-treated liver cells with two lectin-independent chemical enrichment methods.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2018-08-28
    Haopeng Xiao,Ju Eun Hwang,Ronghu Wu

    Protein N-glycosylation is essential for mammalian cell survival and is well-known to be involved in many biological processes. Aberrant glycosylation is directly related to human disease including cancer and infectious diseases. Global analysis of protein N-glycosylation will allow a better understanding of protein functions and cellular activities. Mass spectrometry (MS)-based proteomics provides a unique opportunity to site-specifically characterize protein glycosylation on a large scale. Due to the complexity of biological samples, effective enrichment methods are critical prior to MS analysis. Here, we compared two lectin-independent methods to enrich glycopeptides for the global analysis of protein N-glycosylation by MS. The first boronic acid-based enrichment (BA) method benefits from the universal and reversible interactions between boronic acid and sugars; the other method utilizes metabolic labeling and click chemistry (MC) to incorporate a chemical handle into glycoproteins for future affinity enrichment. We comprehensively compared the performance of the two methods in the identification and quantification of glycoproteins in statin-treated liver cells. Based on the current results, the BA method is more universal in enriching glycopeptides, while with the MC method, cell surface glycoproteins were highly enriched, and the quantification results appear to be more dynamic because only the newly-synthesized glycoproteins were analyzed. In addition, we normalized the glycosylation site ratios by the corresponding parent protein ratios to reflect the real modification changes. In combination with MS-based proteomics, effective enrichment methods will vertically advance protein glycosylation research.

    更新日期:2019-11-01
  • Infrared Multiple Photon Dissociation Spectroscopy of Cationized Canavanine: Side-Chain Substitution Influences Gas-Phase Zwitterion Formation†.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2018-07-03
    Zachary M Smith,Vincent Steinmetz,Jonathan Martens,Jos Oomens,John C Poutsma

    Infrared multiple photon dissociation spectroscopy was performed on protonated and cationized canavanine (Cav), a non-protein amino acid oxy-analog of arginine. Infrared spectra in the XH stretching region (3000 - 4000 cm-1) were obtained at the Centre Laser Infrarouge d'Orsay (CLIO) facility. Comparison of the experimental infrared spectra with scaled harmonic frequencies at the B3LYP/6-31+G(d,p) level of theory indicates that canavanine is in a canonical neutral form in CavH+, CavLi+, and CavNa+; therefore, these cations are charge-solvated structures. The infrared spectrum of CavK+ is consistent with a mixture of Cav in canonical and zwitterionic forms leading to both charge-solvated and salt-bridged cationic structures. The Cav moiety in CavCs+ is shown to be zwitterionic, forming a salt-bridged structure for the cation. Infrared spectra in the fingerprint region (1000 - 2000 cm-1) obtained at the FELIX Laboratory in Nijmegen, Netherlands support these assignments. These results show that that a single oxygen atom substitution in the side chain reduces the stability of the zwitterion compared to that of the protein amino acid arginine (Arg), which has been shown previously to adopt a zwitterionic structure in ArgNa+ and ArgK+. This difference can be explained in part due to the decreased basicity of Cav (PA = 1001 kJ/mol) as compared to arginine (PA = 1051 kJ/mol), but not entirely, as lysine, which has nearly the same proton affinity as Cav, (~993 kJ/mol) forms only canonical structures with Na+, K+, and Cs+. A major difference between the zwitterionic forms of ArgM+ and CavM+ is that the protonation site is on the side chain for Arg and on the N-terminus for Cav. This results in systematically weaker salt bridges in the Cav zwitterions. In addition, the presence of another hydrogen-bonding acceptor atom in the side chain contributes to the stability of the canonical structures for the smaller alkali cations.

    更新日期:2019-11-01
  • Two-Dimensional Separation Using High-pH and Low-pH Reversed Phase Liquid Chromatography for Top-down Proteomics.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2019-05-18
    Zhe Wang,Hongyan Ma,Kenneth Smith,Si Wu

    Advancements in chromatographic separation are critical to in-depth top-down proteomics of complex intact protein samples. Reversed-phase liquid chromatography is the most prevalent technique for top-down proteomics. However, in cases of high complexities and large dynamic ranges, 1D-RPLC may not provide sufficient coverage of the proteome. To address these challenges, orthogonal separation techniques are often combined to improve the coverage and the dynamic range of detection. In this study, a "salt-free" high-pH RPLC was evaluated as an orthogonal dimension of separation to conventional low-pH RPLC with top-down MS. The RPLC separations with low-pH conditions (pH=2) and high-pH conditions (pH=10) were compared to confirm the good orthogonality between high-pH and low-pH RPLC's. The offline 2D RPLC-RPLC-MS/MS analyses of intact E. coli samples were evaluated for the improvement of intact protein identifications as well as intact proteoform characterizations. Compared to the 163 proteins and 328 proteoforms identified using a 1D RPLC-MS approach, 365 proteins and 886 proteoforms were identified using the 2D RPLC-RPLC top-down MS approach. Our results demonstrate that the 2D RPLC-RPLC top-down approach holds great potential for in-depth top-down proteomics studies by utilizing the high resolving power of RPLC separations and by using mass spectrometry compatible buffers for easy sample handling for online MS analysis.

    更新日期:2019-11-01
  • Protonation of Curcumin Triggers Sequential Double Cyclization in the Gas-Phase: An Electrospray Mass Spectrometry and DFT Study.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2019-05-14
    June Cyriac,Justin Paulose,M George,R Srinivas,Daryl Giblin,Michael L Gross

    ESI-protonated natural curcumin (1) undergoes gas-phase cyclization and dissociates via competitive expulsions of 2-methoxy phenol and C4H4O2 (diketene or an isomer). Evidence from mechanistic mass spectrometry and from Density Functional Theory (DFT) reveals that a two-step sequential cyclization occurs for the protonated molecule prior to the unusual loss of the elements of 2-methoxy phenol. Furthermore, the presence of the methoxy group at postion-3 is essential for the second cyclization. The transformation of curcumin upon protonation in the gas phase may be predictive of its solution chemistry and explain how curcumin plays a protective role in biology.

    更新日期:2019-11-01
  • Specific N-Linked Glycosylation Patterns in Areas of Necrosis in Tumor Tissues.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2019-04-30
    Danielle A Scott,Kim Norris-Caneda,Laura Spruill,Evelyn Bruner,Yuko Kono,Peggi M Angel,Anand S Mehta,Richard R Drake

    Tissue necrosis is a form of cell death common in advanced and aggressive solid tumors, and is associated with areas of intratumoral chronic ischemia. The histopathology of necrotic regions appear as a scaffold of cellular membrane remnants, reflective of the hypoxia and cell degradation events associated with this cellular death pathway. Changes in the glycosylation of cell surface proteins is another common feature of cancer progression. Using a recently developed mass spectrometry imaging approach to evaluate N-linked glycan distributions in human formalin-fixed clinical cancer tissues, differences in the glycan structures of regions of tumor, stroma and necrosis were evaluated. While the structural glycan classes detected in the tumor and stromal regions are typically classified as high mannose or branched glycans, the glycans found in necrotic regions displayed limited branching, contained sialic acid modifications and lack fucose modifications. While this phenomenon was initially classified in breast cancer tissues, it has been also seen in cervical, thyroid and liver cancer samples. These changes in glycosylation within the necrotic regions could provide further mechanistic insight to necrotic changes in cancer tissue and provide new research directions for identifying prognostic markers of necrosis.

    更新日期:2019-11-01
  • Multiple TOF/TOF Events in a Single Laser Shot for Multiplexed Lipid Identifications in MALDI Imaging Mass Spectrometry.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2019-03-25
    Boone M Prentice,Josiah C McMillen,Richard M Caprioli

    Tandem mass spectrometry (MS/MS) is often used to identify lipids in matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI IMS) workflows. The molecular specificity afforded by MS/MS is crucial on MALDI time-of-flight (TOF) platforms that generally lack high resolution accurate mass measurement capabilities. Unfortunately, imaging MS/MS workflows generally only monitor a single precursor ion over the imaged area, limiting the throughput of this methodology. Herein, we demonstrate that multiple TOF/TOF events performed in each laser shot can be used to improve the throughput of imaging MS/MS. This is shown to enable the simultaneous identification of multiple phosphatidylcholine lipids in rat brain tissue. Uniquely, the separation in time achieved for the precursor ions in the TOF-1 region of the instrument is maintained for the fragment ions as they are analyzed in TOF-2, allowing for the differentiation of fragment ions of the exact same m/z derived from different precursor ions (e.g., the m/z 163 fragment ion from precursor ion m/z 772.5 is easily distinguished from the m/z 163 fragment ion from precursor ion m/z 826.5). This multiplexed imaging MS/MS approach allows for the acquisition of complete fragment ion spectra for multiple precursor ions per laser shot.

    更新日期:2019-11-01
  • Multiple solution structures of the disordered peptide indolicidin from IMS-MS analysis.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2019-03-25
    Neelam Khanal,Maissa M Gaye,David E Clemmer

    The solution-favored conformations of the 13-residue disordered peptide, indolicidin (Ile1-Leu2-Pro3-Trp4-Lys5-Trp6-Pro7-Trp8-Trp9-Pro10-Trp11-Arg12-Arg13), are evaluated using electrospray ionization (ESI) coupled to ion mobility spectrometry-mass spectrometry (IMS-MS). The ESI-IMS-MS distributions for the dominant [M+4H]4+ ions indicate that three populations of structures coexist in a range of aqueous to non-aqueous solutions (water:dioxane, water:trifluoroethanol, and water:hexafluoroisopropanol). Conformer types and their relative abundances change in response to different solution environments suggesting that the gas phase conformers reflect on the solution populations present in different solvent environments. Collisional activation of isolated gas phase conformations with IMS-IMS-MS experiments provides additional insight about the relative stabilities of different structural types in the absence of solvent. Simulated annealing studies suggest that proline configuration may be important for the presence of multiple conformations.

    更新日期:2019-11-01
  • Discovery and targeted monitoring of polychlorinated biphenyl metabolites in blood plasma using LC-TIMS-TOF MS.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2018-06-20
    Kendra J Adams,Natalie F Smith,Cesar E Ramirez,Francisco Fernandez-Lima

    In the present work, the potential for rapid, targeted analysis of hydroxylated metabolites of polychlorinated biphenyls (OH-PCBs) in diluted human blood plasma using liquid chromatography coupled with trapped ion mobility spectrometry and TOF high resolution mass spectrometry (LC-TIMS-TOF MS) was evaluated. Experimental OH-PCB collisional cross section (CCSN2) and gas-phase candidate structures (<3% error) are reported for the first time and used, in addition to the LC retention time and accurate m/z, as OH-PCB identification features in order to increase the detection selectivity. The proposed LC-TIMS-TOF MS workflow combines a "dilute-and-shoot" sample preparation strategy, a robust liquid chromatography step, a high-resolving power mobility separation (R ~ 150-250) and high-resolution mass spectrometry (R ~ 30-40k) for the separation, identification and quantification of common OH-PCB isomers with limits of detection comparable to traditional workflows (e.g., LOD and LOQ of ~10 pg/mL and ~50 pg/mL, respectively). The higher selectivity and low detection limits provides multiple advantages compared to current methodologies that typically require long, labor-intensive preparation and/or derivatization steps prior to gas or liquid chromatography-mass spectrometry.

    更新日期:2019-11-01
  • Conformational Landscapes of Ubiquitin, Cytochrome c, and Myoglobin: Uniform Field Ion Mobility Measurements in Helium and Nitrogen Drift Gas.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2018-06-20
    Jody C May,Ewa Jurneczko,Sarah M Stow,Isabel Kratochvil,Stefan Kalkhof,John A McLean

    In this study, a commercial uniform field drift tube ion mobility-mass spectrometer (IM-MS) was utilized to measure the gas-phase conformational populations of three well-studied proteins: ubiquitin (8566 Da), cytochrome c (12,359 Da), and myoglobin in both apo and holo forms (16,951 and 17,567 Da, respectively) in order to evaluate the use of this technology for broadscale structural proteomics applications. Proteins were electrosprayed from either acidic organic (pH ~3) or aqueous buffered (pH ~6.6) solution phase conditions, which generated a wide range of cation charge states corresponding to both extended (unfolded) and compact (folded) gas-phase conformational populations. Corresponding collision cross section (CCS) measurements were compiled for significant ion mobility peak features observed at each charge state in order to map the conformational landscapes of these proteins in both helium and nitrogen drift gases. It was observed that the conformational landscapes were similar in both drift gases, with differences being attributed primarily to ion heating during helium operation due to the necessity of operating the instrument with higher pressure differentials. Higher resolving powers were observed in nitrogen, which allowed for slightly better structural resolution of closely-spaced conformer populations. The instrumentation was found to be particularly adept at measuring low abundance conformers which are only present under gentle conditions which minimize ion heating. This work represents the single largest ion mobility CCS survey published to date for these three proteins with 266 CCS values and 117 ion mobility spectra, many of which have not been previously reported.

    更新日期:2019-11-01
  • Novel Peptide Ion Chemistry Associated with Gold (I) Cationization: Preferential Cleavage at Lysine Residues.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2018-06-09
    David J Foreman,Stella K Betancourt,Alice L Pilo,Scott A McLuckey

    Novel peptide ion chemistry associated with gold (I) cationization is described. Cation switching ion/ion reactions, involving gold dichloride reagent anion, [AuCl2]-, are used to replace protons with a gold (I) cation on a polypeptide. Collision induced dissociation of aurated, lysine-containing peptides results in the elimination of gold hydride and ammonia, generating a [M - H - NH3]+ oxidized species. The oxidized product is likely a cyclic iminium ion. This fragmentation pathway is specific to lysine side-chains as polypeptides containing arginine or histidine in the absence of lysine were not observed to form the oxidized product. While oxidation can occur on N-terminal, internal, and C-terminal lysine residues, it is observed to a lesser extent at lysines found at internal and C-terminal positions. However, isolation and subsequent activation of the [M - H - NH3]+ species derived from the internal or C-terminal positions results in preferential cleavage N-terminal to the oxidized lysine residue. This chemistry has been demonstrated using a variety of model peptides and has also been applied to the analysis of melittin.

    更新日期:2019-11-01
  • Enhancing Sensitivity of Liquid Chromatography-Mass Spectrometry of Peptides and Proteins Using Supercharging Agents.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2018-05-12
    Michael Nshanian,Rajeswari Lakshmanan,Hao Chen,Rachel R Ogorzalek Loo,Joseph A Loo

    Trifluoroacetic acid (TFA) is often used as a mobile phase modifier to enhance reversed phase chromatographic performance. TFA adjusts solution pH and is an ion-pairing agent, but it is not typically suitable for electrospray ionization-mass spectrometry (ESI-MS) and liquid chromatography/MS (LC/MS) because of its significant signal suppression. Supercharging agents elevate peptide and protein charge states in ESI, increasing tandem MS (MS/MS) efficiency. Here, LC/MS protein supercharging was effected by adding agents to LC mobile phase solvents. Significantly, the ionization suppression generally observed with TFA was, for the most part, rescued by supercharging agents, with improved separation efficiency (higher number of theoretical plates) and lowered detection limits.

    更新日期:2019-11-01
  • Parallel detection in a single ICR cell: Spectral averaging and improved S/N without increased acquisition time.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2018-05-08
    Sung-Gun Park,Gordon A Anderson,James E Bruce

    Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) is well-renowned for its ultrahigh resolving power and mass measurement accuracy. As with other types of analytical instrumentation, achievable signal-to-noise ratio (S/N) is an important analytical figure of merit with FTICR-MS. S/N can be improved with higher magnetic fields and longer time-domain signal acquisition periods. However, serial signal averaging of spectra or time-domain signals acquired with multiple ion populations is most commonly used to improve S/N. On the other hand, serial acquisition and averaging of multiple scans significantly increases required data acquisition time and is often incompatible with on-line chromatographic separations. In this study, we investigated the potential for increased S/N by averaging 4 spectra that were acquired in parallel with a single ICR cell with 4 pairs of dipole detection electrodes, each with an independent pre-amplifier. This spectral averaging was achieved with no need for multiple ion accumulation events nor multiple, serial excitation and detection events. These efforts demonstrated that parallel signal acquisition with 4 detector electrode pairs produces S/N 1.76-fold higher than that from a single detection electrode pair. With parallel detection, improved S/N was achieved with no observable loss in resolving power (100,000) as compared with that from a single detection electrode pair. These results demonstrate that parallel detection of multiple induced image current signals with multiple preamplifiers exists as a viable option for future instrumentation to increase achievable S/N and sensitivity. This approach may have general utility especially where conventional serial signal averaging is impractical.

    更新日期:2019-11-01
  • Proteome changes in the aging Drosophila melanogaster head.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2019-03-25
    Christopher J Brown,Thomas Kaufman,Jonathan C Trinidad,David E Clemmer

    A combination of liquid chromatography, ion mobility spectrometry, mass spectrometry, and database searching techniques were used to characterize the proteomes of four biological replicates of adult Drosophila melanogaster heads at seven time points across their lifespans. Based on the detection of tryptic peptides, the identities of 1281 proteins were determined. An estimate of the abundance of each protein, based on the three most intense peptide ions, shows that the quantified species vary in concentration over a factor of ~103. Compared to initial studies in the field of Drosophila proteomics, our current results show an eight-fold higher temporal protein coverage with increased quantitative accuracy. Across the lifespan, we observe a range of trends in the abundance of different proteins, including: an increase in abundance of proteins involved in oxidative phosphorylation, and the tricarboxylic acid cycle; a decrease in proteasomal proteins, as well as ribosomal proteins; and, many types of proteins, which remain relatively unchanged. For younger flies, proteomes are relatively similar within their age group. For older flies, proteome similarity decreases within their age group. These combined results illustrate a correlation between increasing age and decreasing proteostasis.

    更新日期:2019-11-01
  • Comprehensive urinary metabolomic characterization of a genetically induced mouse model of prostatic inflammation.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2019-03-16
    Ling Hao,Yatao Shi,Samuel Thomas,Chad M Vezina,Sagar Bajpai,Arya Ashok,Charles J Bieberich,William A Ricke,Lingjun Li

    Dysfunction of the lower urinary tract commonly afflicts the middle-aged and aging male population. The etiology of lower urinary tract symptoms (LUTS) is multifactorial. Benign prostate hyperplasia, fibrosis, smooth muscle contractility, and inflammation likely contribute. Here we aim to characterize the urinary metabolomic profile associated with prostatic inflammation, which could inform future personalized diagnosis or treatment, as well as mechanistic research. Quantitative urinary metabolomics was conducted to examine molecular changes following induction of inflammation via conditional Interleukin-1β expression in prostate epithelia using a novel transgenic mouse strain. To advance method development for urinary metabolomics, we also compared different urine normalization methods and found that normalizing urine samples based on osmolality prior to LC-MS most completely separated urinary metabolite profiles of mice with and without prostate inflammation via principal component analysis. Global metabolomics was combined with advanced machine learning feature selection and classification for data analysis. Key dysregulated metabolites and pathways were identified and were relevant to prostatic inflammation, some of which overlapped with our previous study of human LUTS patients. A binary classification model was established via the support vector machine algorithm to accurately differentiate control and inflammation groups, with an area-under-the-curve value of the receiver operating characteristic of 0.81, sensitivity of 0.974 and specificity of 0.995, respectively. This study generated molecular profiles of non-bacterial prostatic inflammation, which could assist future efforts to stratify LUTS patients and develop new therapies.

    更新日期:2019-11-01
  • High-precision molybdenum isotope analysis by negative thermal ionization mass spectrometry.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2016-08-20
    Emily A Worsham,Richard J Walker,Katherine R Bermingham

    Procedures for the separation, purification, and high-precision analysis of mass-independent isotopic variations in molybdenum (Mo) using negative thermal ionization mass spectrometry are reported. Separation and purification of Mo from silicate and metal matrices are achieved using a two-stage anion exchange chromatographic procedure. Molybdenum is ionized as the MoO3 - species using a double filament assembly. The MoO3 - ion beams are collected using Faraday cup detectors equipped with a mixed array of amplifiers utilizing 1011 and 1012 Ω resistors, which allows for in situ measurement and correction of oxygen isobars. The long-term external reproducibility of 97Mo/96Mo, the most precisely measured Mo isotope ratio, is ±5.4 ppm (2SD), based on the repeated analyses of the Alfa Aesar Specpure ® Mo plasma standard and using 98Mo/96Mo for fractionation correction. The long-term external reproducibilities of 92Mo/96Mo, 94Mo/96Mo, 95Mo/96Mo, and 100Mo/96Mo are ±107, 37, 23, and 32 ppm (2SD), respectively. With this precision, smaller differences in Mo isotopic compositions can be resolved than have been previously possible.

    更新日期:2019-11-01
  • High-precision analysis of 182W/184W and 183W/184W by negative thermal ionization mass spectrometry: Per-integration oxide corrections using measured 18O/16O.
    Int. J. Mass Spectrom. (IF 1.658) Pub Date : 2017-03-01
    Gregory J Archer,Andrea Mundl,Richard J Walker,Emily A Worsham,Katherine R Bermingham

    Here we describe a new analytical technique for the high-precision measurement of 182W/184W and 183W/184W using negative thermal ionization mass spectrometry (N-TIMS). We improve on the recently reported method of Trinquier et al. (2016), which described using Faraday cup collectors coupled with amplifiers utilizing 1013 Ω resistors to continuously monitor the 18O/16O of WO3 - and make per-integration oxide corrections. In our study, we report and utilize a newly measured oxygen mass fractionation line, as well as average 17O/16O and 18O/16O, which allow for more accurate per-integration oxide interference corrections. We also report a Faraday cup and amplifier configuration that allows 18O/16O to be continuously monitored for WO3 - and ReO3 -, both of which are ionized during analyses of W using Re ribbon. The long-term external precision of 182W/184W is 5.7 ppm and 3.7 ppm (2SD) when mass bias corrected using 186W/184W and 186W/183W, respectively. For 183W/184W mass bias is corrected using 186W/184W, yielding a long-term external precision of 6.6 ppm. An observed, correlated variation in 182W/184W and 183W/184W, when mass bias corrected using 186W/184W, is most likely the result of Faraday cup degradation over months-long intervals.

    更新日期:2019-11-01
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