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International Journal of Mass Spectrometry

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...
July 2017: International Journal of Mass Spectrometry
Pengfei Li, William D Hoffmann, Glen P Jackson
We herein demonstrate an approach to gas phase ion manipulation that provides MS(3)-level CID spectra of phospholipid radical cations that are almost independent of the original charging adduct ions. In the MS(2) He-MAD spectra of the protonated, sodiated and potassiated adducts of POPC, the different adducts induce different primary fragmentation pathways and provide significantly different spectra, as is commonly observed by other activation methods. In separate experiments, the even-electron adduct ions ([M+H](+), [M+Na](+), [M+K](+)) of 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) were first converted to radical cations [POPC](+(•)) by using helium metastable atom-activated dissociation (He-MAD) to eject the charging adduct ions, then exposed to low-energy collision induced dissociation (CID) to induce extensive fragmentation along the acyl chains...
June 1, 2016: International Journal of Mass Spectrometry
Si Cheng, Jun Wang, Yi Cai, Joseph A Loo, Hao Chen
Desorption electrospray ionization mass spectrometry (DESI-MS) is a recent and important advance in the field that has extensive applications in surface analysis of solid samples but has also been extended to analysis of liquid samples. The liquid sample DESI typically employs a piece of fused silica capillary to transfer liquid sample for ionization. In this study, we present the improvement of liquid sample DESI-MS by replacing the sample transfer silica capillary with a trap column filled with chromatographic stationary phase materials (e...
December 3, 2015: International Journal of Mass Spectrometry
Dominika Strzelecka, Stephen W Holman, Claire E Eyers
Dimethyl sulfoxide (DMSO) has been advocated as a beneficial additive to electrospray solvents for peptide analysis due to the improved ionisation efficiency conferred. Previous reports have shown that the resultant improvements in peptide ion signal intensities are non-uniform. As a result, it was hypothesised that inclusion of DMSO in electrospray solvents could be detrimental to the outcome of intensity-based label-free absolute quantification approaches, specifically the top 3 method. The effect of DMSO as a mobile phase additive in top 3 label-free quantification was therefore evaluated...
November 30, 2015: International Journal of Mass Spectrometry
Dalila Bensaddek, Armel Nicolas, Angus I Lamond
Despite many recent advances in instrumentation, the sheer complexity of biological samples remains a major challenge in large-scale proteomics experiments, reflecting both the large number of protein isoforms and the wide dynamic range of their expression levels. However, while the dynamic range of expression levels for different components of the proteome is estimated to be ∼10(7-8), the equivalent dynamic range of LC-MS is currently limited to ∼10(6). Sample pre-fractionation has therefore become routinely used in large-scale proteomics to reduce sample complexity during MS analysis and thus alleviate the problem of ion suppression and undersampling...
November 30, 2015: International Journal of Mass Spectrometry
Onrapak Reamtong, Krongkan Srimuang, Naowarat Saralamba, Polkit Sangvanich, Nicholas P J Day, Nicholas J White, Mallika Imwong
Malaria is a mosquito borne infectious disease caused by protozoa of genus Plasmodium. There are five species of Plasmodium that are found to infect humans. Plasmodium falciparum can cause severe malaria leading to higher morbidity and mortality of malaria than the other four species. Antimalarial resistance is the major obstacle to control malaria. Mefloquine was used in combination with Artesunate for uncomplicated P. falciparum in South East Asia and it has developed and established mefloquine resistance in this region...
November 30, 2015: International Journal of Mass Spectrometry
Thomas G Watkinson, Antonio N Calabrese, Fabrice Giusti, Manuela Zoonens, Sheena E Radford, Alison E Ashcroft
Membrane proteins (MPs) are essential for numerous important biological processes. Recently, mass spectrometry (MS), coupled with an array of related techniques, has been used to probe the structural properties of MPs and their complexes. Typically, detergent micelles have been employed for delivering MPs into the gas-phase, but these complexes have intrinsic properties that can limit the utility of structural studies of MPs using MS methods. Amphipols (APols) have advantages over detergent micelles and have been shown to be capable of delivering native MPs into the gas-phase...
November 30, 2015: International Journal of Mass Spectrometry
Zhou Peng, Scott A McLuckey
The formation of peptide bonds is of great importance from both a biological standpoint and in routine organic synthesis. Recent work from our group demonstrated the synthesis of peptides in the gas-phase via ion/ion reactions with sulfo-NHS reagents, which resulted in conjugation of individual amino acids or small peptides to the N-terminus of an existing 'anchor' peptide. Here, we demonstrate a complementary approach resulting in the C-terminal extension of peptides. Individual amino acids or short peptides can be prepared as reagents by incorporating gas phase-labile protecting groups to the reactive C-terminus and then converting the N-terminal amino groups to the active ketenimine reagent...
November 30, 2015: International Journal of Mass Spectrometry
Chang Ho Sohn, Sheng Yin, Ivory Peng, Joseph A Loo, J L Beauchamp
The mechanisms of electron capture and electron transfer dissociation (ECD and ETD) are investigated by covalently attaching a free-radical hydrogen atom scavenger to a peptide. The 2,2,6,6-tetramethylpiperidin-l-oxyl (TEMPO) radical was chosen as the scavenger due to its high hydrogen atom affinity (ca. 280 kJ/mol) and low electron affinity (ca. 0.45 ev), and was derivatized to the model peptide, FQX(TEMPO)EEQQQTEDELQDK. The X(TEMPO) residue represents a cysteinyl residue derivatized with an acetamido-TEMPO group...
November 15, 2015: International Journal of Mass Spectrometry
Philip D Compton, Luca Fornelli, Neil L Kelleher, Owen S Skinner
Dissociation of gaseous protein complexes produced by native electrospray often induces an asymmetric partitioning of charge between ejected subunits. We present a simple asymmetric charge partitioning factor (ACPF) to quantify the magnitude of asymmetry in this effect. When applied to monomer ejection from the cytochrome c dimer and β-amylase tetramer, we found that the ~60-70% of precursor charge ending up in the ejected monomers corresponds to ACPFs of 1.38 and 2.51, respectively. Further, we used site-specific fragmentation from electron transfer dissociation (ETD) to identify differences in fragmentation and characterize domains of secondary-structure present in the dimer, ejected monomers, and monomers obtained directly from electrospray ionization (ESI)...
November 15, 2015: International Journal of Mass Spectrometry
Robert E Deimler, Madlen Sander, Glen P Jackson
The fragmentation pattern of several protonated 1+ phosphatidylcholines (PCs) were studied using low energy collision induced dissociation (CID) and helium metastable atom-activated dissociation (He-MAD). He-MAD of the protonated compounds produced a dominant phosphocholine head group at m/z 184 as well as typical sn-1 and sn-2 glycerol fragments such as [M+H-Rx-1CHC=O](+) and [M+H-Rx-1CO2H](+). Within the aliphatic chain, He-MAD showed fragments consistent with high-energy collision induced dissociation (HE-CID) and products/pathways consistent with Penning ionization of the 1+ precursor ions to their respective radical dications...
November 15, 2015: International Journal of Mass Spectrometry
Piriya Wongkongkathep, Huilin Li, Xing Zhang, Rachel R Ogorzalek Loo, Ryan R Julian, Joseph A Loo
The application of ion pre-activation with 266 nm ultraviolet (UV) laser irradiation combined with electron capture dissociation (ECD) is demonstrated to enhance top-down mass spectrometry sequence coverage of disulfide bond containing proteins. UV-based activation can homolytically cleave a disulfide bond to yield two separated thiol radicals. Activated ECD experiments of insulin and ribonuclease A containing three and four disulfide bonds, respectively, were performed. UV-activation in combination with ECD allowed the three disulfide bonds of insulin to be cleaved and the overall sequence coverage to be increased...
November 15, 2015: International Journal of Mass Spectrometry
Xiang Yu, Nadezda P Sargaeva, Christopher J Thompson, Catherine E Costello, Cheng Lin
Deamidation and the subsequent formation of isoaspartic acid (isoAsp) are common modifications of asparagine (Asn) residues in proteins. Differentiation of isoAsp and Asp residues is a challenging task owing to their similar chemical properties and identical molecular mass. Recent studies showed that they can be differentiated using electron capture dissociation (ECD) which generates diagnostic fragments c'+57 and z(•)-57 specific to the isoAsp residue. However, the ECD approach is only applicable towards multiply charged precursor ions and generally does not work for β-amino acids other than isoAsp...
November 15, 2015: International Journal of Mass Spectrometry
Isaac Agyekum, Anish B Patel, Chengli Zong, Geert-Jan Boons, Jonathan Amster
The present work focuses on the assignment of uronic acid stereochemistry in heparan sulfate (HS) oligomers. The structural elucidation of HS glycosaminoglycans is the subject of considerable importance due to the biological and biomedical significance of this class of carbohydrates. They are highly heterogeneous due to their non-template biosynthesis. Advances in tandem mass spectrometry activation methods, particularly electron detachment dissociation (EDD), has led to the development of methods to assign sites of sulfo modification in glycosaminoglycan oligomers, but there are few reports of the assignment of uronic acid stereochemistry, necessary to distinguish glucuronic acid (GlcA) from iduronic acid (IdoA)...
November 15, 2015: International Journal of Mass Spectrometry
Stefan Ralser, Johannes Postler, Martina Harnisch, Andrew M Ellis, Paul Scheier
The availability of high resolution mass spectrometry in the study of atomic and molecular clusters opens up challenges for the interpretation of the data. In complex systems each resolved mass peak may contain contributions from multiple species because of the isotope structure of constituent elements and because a multitude of different types of clusters with different compositions are present. A computational procedure which can help to identify a specific cluster from this complex dataset and quantify its relative abundance would be extremely helpful to many who work in this field...
March 15, 2015: International Journal of Mass Spectrometry
Huong T H Nguyen, Christopher J Shaffer, Aaron R Ledvina, Joshua J Coon, František Tureček
The serine residue displays specific effects on the dissociations of peptide fragment cation-radicals of the z (+•) type which are produced by electron transfer dissociation. Energy-resolved collision-induced dissociation (ER-CID), time-resolved infrared multiphoton dissociation (TR-IRMPD), and single-photon UV photodissociation at 355 nm revealed several competitive dissociation pathways consisting of loss of OH radical, water, and backbone cleavages occurring at N-terminal and C-terminal positions relative to the serine residue...
February 15, 2015: International Journal of Mass Spectrometry
Lucía Geis-Asteggiante, Avantika Dhabaria, Nathan Edwards, Suzanne Ostrand-Rosenberg, Catherine Fenselau
Top-down analysis is reported for a portion of the protein cargo of exosomes shed by myeloid-derived suppressor cells that participate in intracellular signaling in the tumor microenvironment. Instrument mass resolution limited the study to proteins of molecular masses below 30 kDa. A two-step fractionation strategy was used, including open tubular gel electrophoresis and C3 reverse phase high performance liquid chromatography. Twenty-one unique proteins were identified among more than 200 proteoforms, and comprising primarily two functionally important protein families: the S100 proinflammatory mediators and an abundance of histones...
February 15, 2015: International Journal of Mass Spectrometry
Joseph A Hankin, Robert C Murphy, Robert M Barkley, Miguel A Gijón
The tandem mass spectrometry, ion mobility, and normal phase HPLC of isomeric phosphatidylglycerol (PG) and bis(monoacylglycerol)phosphate (BMP) have been investigated in this study with the objective of differentiating these unique classes of lipids. Measurement of ion mobility using the traveling wave method for negative molecular and product ions from isomeric PG and BMP yielded identical results, but different ion mobilities were observed for positive product ions arising from collision-induced dissociation (CID)...
February 15, 2015: International Journal of Mass Spectrometry
Chunxiang Yao, Jun Yu, Linda Taylor, Peter Polgar, Mark E McComb, Catherine E Costello
Pulmonary arterial hypertension (PAH) is a disease characterized by increased pulmonary vascular resistance and remodeling. Increase in the population of vascular smooth muscle cells is among the key events contributing to the remodeling. Endothelin-1 (ET-1), a potent vasoconstrictor, is linked to the etiology and progression of PAH. Here we analyze changes in protein expressions in response to ET-1 in pulmonary arterial smooth muscle cells (PASMC) from a healthy Control (non-PAH) and a PAH subject presenting a bone morphogenetic protein type II receptor (BMPR2) mutation with exon 1-8 deletion...
February 15, 2015: International Journal of Mass Spectrometry
Brendan Prideaux, Mariam S ElNaggar, Matthew Zimmerman, Justin M Wiseman, Xiaohua Li, Véronique Dartois
A multi-modal mass spectrometry imaging (MSI) and profiling approach has been applied to assess the partitioning of the anti-TB fluoroquinolone levofloxacin into pulmonary lesions. Matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) and a commercial liquid microjunction surface sampling technology (LMJ-SSP), or flowprobe, have been used to both spatially profile and image drug distributions in lung tissue sections from TB-infected rabbits following oral administration of a single human-equivalent dose...
February 1, 2015: International Journal of Mass Spectrometry
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