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Su Chen - One of the best experts on this subject based on the ideXlab platform.
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structural elucidatIon of molecular species of pacific oyster ether amino phospholipids by normal phase liquid chromatography Negative Ion Electrospray IonizatIon and quadrupole multiple stage linear Ion trap mass spectrometry
Analytica Chimica Acta, 2012Co-Authors: Su Chen, Natalia A. Belikova, Papasani V. SubbaiahAbstract:Although marine oysters contain abundant amounts of ether-linked aminophospholipids, the structural identificatIon of the various molecular species has not been reported. We developed a normal-phase silica liquid chromatography/Negative-Ion Electrospray IonizatIon/quadrupole multiple-stage linear Ion-trap mass spectrometric (NPLC-NI-ESI/Q-TRAP-MS3) method for the structural elucidatIon of ether molecular species of serine and ethanolamine phospholipids from marine oysters. The major advantages of the approach are (i) to avoid incorrect selectIon of isobaric precursor Ions derived from different phospholipid classes in a lipid mixture, and to generate informative and clear MSn product Ion mass spectra of the species for the identificatIon of the sn-1 plasmanyl or plasmenyl linkages, and (ii) to increase precursor Ion intensities by “concentrating” lipid molecules of each phospholipid class for further structural determinatIon of minor molecular species. Employing a combinatIon of NPLC-NI-ESI/MS3 and NPLC-NI-ESI/MS2, we elucidated, for the first time, the chemical structures of docosahexaenoyl and eicosapentaenoyl plasmenyl phosphatidylserine (PS) species and differentiated up to six isobaric species of diacyl/alkylacyl/alkenylacyl phosphatidylethanolamine (PE) in the US pacific oysters. The presence of a high content of both omega-3 plasmenyl PS/plasmenyl PE species and multiple isobaric molecular species isomers is the noteworthy characteristic of the marine oyster. The simple and robust NPLC-NI-ESI/MSn-based methodology should be particularly valuable in the detailed characterizatIon of marine lipid dietary supplements with respect to omega-3 aminophospholipids.
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Structural elucidatIon of molecular species of pacific oyster ether amino phospholipids by normal-phase liquid chromatography/Negative-Ion Electrospray IonizatIon and quadrupole/multiple-stage linear Ion-trap mass spectrometry
Analytica Chimica Acta, 2012Co-Authors: Su Chen, Natalia A. Belikova, Papasani V. SubbaiahAbstract:Although marine oysters contain abundant amounts of ether-linked aminophospholipids, the structural identificatIon of the various molecular species has not been reported. We developed a normal-phase silica liquid chromatography/Negative-Ion Electrospray IonizatIon/quadrupole multiple-stage linear Ion-trap mass spectrometric (NPLC-NI-ESI/Q-TRAP-MS3) method for the structural elucidatIon of ether molecular species of serine and ethanolamine phospholipids from marine oysters. The major advantages of the approach are (i) to avoid incorrect selectIon of isobaric precursor Ions derived from different phospholipid classes in a lipid mixture, and to generate informative and clear MSn product Ion mass spectra of the species for the identificatIon of the sn-1 plasmanyl or plasmenyl linkages, and (ii) to increase precursor Ion intensities by “concentrating” lipid molecules of each phospholipid class for further structural determinatIon of minor molecular species. Employing a combinatIon of NPLC-NI-ESI/MS3 and NPLC-NI-ESI/MS2, we elucidated, for the first time, the chemical structures of docosahexaenoyl and eicosapentaenoyl plasmenyl phosphatidylserine (PS) species and differentiated up to six isobaric species of diacyl/alkylacyl/alkenylacyl phosphatidylethanolamine (PE) in the US pacific oysters. The presence of a high content of both omega-3 plasmenyl PS/plasmenyl PE species and multiple isobaric molecular species isomers is the noteworthy characteristic of the marine oyster. The simple and robust NPLC-NI-ESI/MSn-based methodology should be particularly valuable in the detailed characterizatIon of marine lipid dietary supplements with respect to omega-3 aminophospholipids.
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ValidatIon of liquid-liquid extractIon followed by flow-injectIon Negative Ion Electrospray mass spectrometry assay to Topiramate in human plasma.
Rapid Communications in Mass Spectrometry, 2001Co-Authors: Su Chen, Paul M. CarveyAbstract:This paper describes the development and validatIon of a method for the quantitative analysis of Topiramate (2,3:4,5-bis-O-(1-methylethylidene)-β-D-fructopyranose sulfamate), a new antiepileptic drug, in human plasma using liquid-liquid extractIon followed by flow-injectIon Negative Ion Electrospray mass spectrometry. Using Prednisone (1,4-pregnadiene-17-α,21-diol-3,11,20-trIone [10 µg/mL]) as an internal standard, calibratIon curves for Topiramate were linear over a range of 1 to 30 µg/mL in human plasma and were highly reliable (r2 = 0.9991). The lower limit of quantitatIon of the assay was 2 µg/mL in human plasma. PrecisIon (%CV
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validatIon of liquid liquid extractIon followed by flow injectIon Negative Ion Electrospray mass spectrometry assay to topiramate in human plasma
Rapid Communications in Mass Spectrometry, 2001Co-Authors: Su Chen, Paul M. CarveyAbstract:This paper describes the development and validatIon of a method for the quantitative analysis of Topiramate (2,3:4,5-bis-O-(1-methylethylidene)-β-D-fructopyranose sulfamate), a new antiepileptic drug, in human plasma using liquid-liquid extractIon followed by flow-injectIon Negative Ion Electrospray mass spectrometry. Using Prednisone (1,4-pregnadiene-17-α,21-diol-3,11,20-trIone [10 µg/mL]) as an internal standard, calibratIon curves for Topiramate were linear over a range of 1 to 30 µg/mL in human plasma and were highly reliable (r2 = 0.9991). The lower limit of quantitatIon of the assay was 2 µg/mL in human plasma. PrecisIon (%CV <15%) and accuracy (<20%) for both intra- and inter-day validatIons were satisfactory. The method has been used in clinical pharmacology research. Copyright © 2001 John Wiley & Sons, Ltd.
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Rapid approach to the quantitative determinatIon of Topiramate (2,3:4,5-bis-O-(1-methylethylidene)-β-D-fructopyranose sulfamate) in human plasma by liquid–liquid extractIon and flow-injectIon Negative-Ion Electrospray mass spectrometry
Rapid Communications in Mass Spectrometry, 1999Co-Authors: Su Chen, Paul M. CarveyAbstract:Topiramate, a sulfamate-substituted monosaccharide (2,3:4,5-bis-O-(1-methylethylidene)-β-D-fructopyranose sulfamate), is a new antiepileptic drug, which has been approved for adjunctive therapy in adult patients with partial-onset seizures. Liquid-liquid extractIon followed by flow-injectIon Negative-Ion Electrospray mass spectrometry was evaluated as a means for the quantitative analysis of Topiramate in human plasma. Prednisone (1,4-pregnadiene-17-α,21-diol-3,11,20-trIone [15 µg/mL]) was used as the internal standard because its solubility and molecular weight are similar to those of Topiramate. CalibratIon curves for Topiramate were linear over a range of 1 to 30 µg/mL plasma (signal-to-noise ratio >4) and were highly reliable (r2 = 0.994). This approach offers several advantages: (i) the extractIon of Topiramate from human plasma using chloroform is simple and reproducible; (ii) the quantitative determinatIon of Topiramate, in the presence of an internal standard, by flow-injectIon Negative-Ion Electrospray mass spectrometry with selected-Ion recording, is rapid and accurate and does not require chromatographic separatIon; (iii) the assay possesses adequate sensitivity (2–25 µg/mL) for the quantitative analysis of Topiramate in plasma from patients. Copyright © 1999 John Wiley & Sons, Ltd.
Wengang Chai - One of the best experts on this subject based on the ideXlab platform.
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Profiling of Human Milk Oligosaccharides for Lewis Epitopes and Secretor Status by Electrostatic RepulsIon Hydrophilic InteractIon Chromatography Coupled with Negative-Ion Electrospray Tandem Mass Spectrometry.
Analytical Chemistry, 2019Co-Authors: Jingyu Yan, Junjie Ding, Gaowa Jin, Zhimou Guo, Zhao-jun Duan, Fan Yang, Han Zhou, Wengang ChaiAbstract:Human milk oligosaccharides (HMOs) are one of the most abundant ingredients in breast milk, and they play a beneficial role for newborns and are important for infant health. The peripheral fucosylated sequences of HMOs, such as the histo-blood group ABH(O) and Lewis a, b, x, and y antigens, are determined by the expressIon of the secretor (Se) and Lewis (Le) genes in the mammary gland, and are often the recognitIon motifs and serve as decoy receptors for microbes. In this work, we developed a method for determinatIon of secretor status and Lewis blood phenotype and assignment of Lewis blood-group epitopes. The method was based on electrostatic repulsIon/hydrophilic interactIon chromatography coupled with tandem mass spectrometry (ERLIC-MS/MS). A specifically designed statIonary phase, aspartic acid-bonded silica (ABS), was used to separate the acidic and neutral HMOs by electrostatic repulsIon followed by HILIC. Negative-Ion Electrospray MS/MS was then used for analysis of secretor status and Lewis blood phenotypes and assignment of important epitopes of HMOs from the lactating mothers by selecting a specific set of unique fragment Ions.
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Profiling of Human Milk Oligosaccharides for Lewis Epitopes and Secretor Status by Electrostatic RepulsIon Hydrophilic InteractIon Chromatography Coupled with Negative-Ion Electrospray Tandem Mass Spectrometry
2019Co-Authors: Jingyu Yan, Junjie Ding, Gaowa Jin, Zhimou Guo, Zhao-jun Duan, Fan Yang, Han Zhou, Wengang ChaiAbstract:Human milk oligosaccharides (HMOs) are one of the most abundant ingredients in breast milk, and they play a beneficial role for newborns and are important for infant health. The peripheral fucosylated sequences of HMOs, such as the histo-blood group ABH(O) and Lewis a, b, x, and y antigens, are determined by the expressIon of the secretor (Se) and Lewis (Le) genes in the mammary gland, and are often the recognitIon motifs and serve as decoy receptors for microbes. In this work, we developed a method for determinatIon of secretor status and Lewis blood phenotype and assignment of Lewis blood-group epitopes. The method was based on electrostatic repulsIon/hydrophilic interactIon chromatography coupled with tandem mass spectrometry (ERLIC–MS/MS). A specifically designed statIonary phase, aspartic acid-bonded silica (ABS), was used to separate the acidic and neutral HMOs by electrostatic repulsIon followed by HILIC. Negative-Ion Electrospray MS/MS was then used for analysis of secretor status and Lewis blood phenotypes and assignment of important epitopes of HMOs from the lactating mothers by selecting a specific set of unique fragment Ions
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Assignment by Negative-Ion Electrospray Tandem Mass Spectrometry of the Tetrasaccharide Backbones of Monosialylated Glycans Released from Bovine Brain Gangliosides.
Journal of The American Society for Mass Spectrometry, 2018Co-Authors: Wengang Chai, Yibing Zhang, Barbara Mulloy, Laura Mauri, Maria Grazia Ciampa, Sandro Sonnino, Ten FeiziAbstract:Gangliosides, as plasma membrane-associated sialylated glycolipids, are antigenic structures and they serve as ligands for adhesIon proteins of pathogens, for toxins of bacteria, and for endogenous proteins of the host. The detectability by carbohydrate-binding proteins of glycan antigens and ligands on glycolipids can be influenced by the differing lipid moieties. To investigate glycan sequences of gangliosides as recognitIon structures, we have underway a program of work to develop a “gangliome” microarray consisting of isolated natural gangliosides and neoglycolipids (NGLs) derived from glycans released from them, and each linked to the same lipid molecule for arraying and comparative microarray binding analyses. Here, in the first phase of our studies, we describe a strategy for high-sensitivity assignment of the tetrasaccharide backbones and applicatIon to identificatIon of eight of monosialylated glycans released from bovine brain gangliosides. This approach is based on Negative-Ion Electrospray mass spectrometry with collisIon-induced dissociatIon (ESI-CID-MS/MS) of the desialylated glycans. Using this strategy, we have the data on backbone regIons of four minor components among the monosialo-ganglioside-derived glycans; these are of the ganglio-, lacto-, and neolacto-series.
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profiling of sialylated oligosaccharides in mammalian milk using online solid phase extractIon hydrophilic interactIon chromatography coupled with Negative Ion Electrospray mass spectrometry
Analytical Chemistry, 2018Co-Authors: Jingyu Yan, Wengang Chai, Junjie Ding, Gaowa Jin, Zhen Long, Zhimou Guo, Xinmiao LiangAbstract:Sialylated oligosaccharides are important components in mammalian milk. They play a key role in the health and growth of infants by helping to shape up infant's gastrointestinal microbiota and defense against infectIon by various pathogenic agents. A detailed knowledge of the structures, compositIons, and quantities of the sialylated milk oligosaccharides (SMOs) is a prerequisite for understanding their biological roles. However, because of the presence of very large amounts of lactose and neutral oligosaccharides, accurate analysis of SMOs is difficult. A pretreatment step is required to remove lactose and neutral oligosaccharides but conventIonal off-line pretreatment methods are time-consuming and of poor reproducibility. In this presentatIon, we linked solid-phase extractIon (SPE) with hydrophilic interactIon chromatography (HILIC) followed by mass spectrometry (MS) identificatIon for the analysis of SMOs. A SPE column with electrostatic repulsIon functIon was used for removal of lactose and neutral oligosaccharides, a HILIC analytical column for separatIon of the SMOs, and Negative-Ion Electrospray IonizatIon tandem MS was used for their identificatIon and sequencing. The success of the established online SPE-HILIC-MS method was demonstrated by profiling of SMOs in human to investigate detailed SMO changes during lactatIon period and in animals to compare the difference in SMO contents among the different species.
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Profiling of Sialylated Oligosaccharides in Mammalian Milk Using Online Solid Phase ExtractIon-Hydrophilic InteractIon Chromatography Coupled with Negative-Ion Electrospray Mass Spectrometry
2018Co-Authors: Jingyu Yan, Wengang Chai, Junjie Ding, Gaowa Jin, Zhen Long, Zhimou Guo, Xinmiao LiangAbstract:Sialylated oligosaccharides are important components in mammalian milk. They play a key role in the health and growth of infants by helping to shape up infant’s gastrointestinal microbiota and defense against infectIon by various pathogenic agents. A detailed knowledge of the structures, compositIons, and quantities of the sialylated milk oligosaccharides (SMOs) is a prerequisite for understanding their biological roles. However, because of the presence of very large amounts of lactose and neutral oligosaccharides, accurate analysis of SMOs is difficult. A pretreatment step is required to remove lactose and neutral oligosaccharides but conventIonal off-line pretreatment methods are time-consuming and of poor reproducibility. In this presentatIon, we linked solid-phase extractIon (SPE) with hydrophilic interactIon chromatography (HILIC) followed by mass spectrometry (MS) identificatIon for the analysis of SMOs. A SPE column with electrostatic repulsIon functIon was used for removal of lactose and neutral oligosaccharides, a HILIC analytical column for separatIon of the SMOs, and Negative-Ion Electrospray IonizatIon tandem MS was used for their identificatIon and sequencing. The success of the established online SPE-HILIC-MS method was demonstrated by profiling of SMOs in human to investigate detailed SMO changes during lactatIon period and in animals to compare the difference in SMO contents among the different species
Paul M. Carvey - One of the best experts on this subject based on the ideXlab platform.
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ValidatIon of liquid-liquid extractIon followed by flow-injectIon Negative Ion Electrospray mass spectrometry assay to Topiramate in human plasma.
Rapid Communications in Mass Spectrometry, 2001Co-Authors: Su Chen, Paul M. CarveyAbstract:This paper describes the development and validatIon of a method for the quantitative analysis of Topiramate (2,3:4,5-bis-O-(1-methylethylidene)-β-D-fructopyranose sulfamate), a new antiepileptic drug, in human plasma using liquid-liquid extractIon followed by flow-injectIon Negative Ion Electrospray mass spectrometry. Using Prednisone (1,4-pregnadiene-17-α,21-diol-3,11,20-trIone [10 µg/mL]) as an internal standard, calibratIon curves for Topiramate were linear over a range of 1 to 30 µg/mL in human plasma and were highly reliable (r2 = 0.9991). The lower limit of quantitatIon of the assay was 2 µg/mL in human plasma. PrecisIon (%CV
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validatIon of liquid liquid extractIon followed by flow injectIon Negative Ion Electrospray mass spectrometry assay to topiramate in human plasma
Rapid Communications in Mass Spectrometry, 2001Co-Authors: Su Chen, Paul M. CarveyAbstract:This paper describes the development and validatIon of a method for the quantitative analysis of Topiramate (2,3:4,5-bis-O-(1-methylethylidene)-β-D-fructopyranose sulfamate), a new antiepileptic drug, in human plasma using liquid-liquid extractIon followed by flow-injectIon Negative Ion Electrospray mass spectrometry. Using Prednisone (1,4-pregnadiene-17-α,21-diol-3,11,20-trIone [10 µg/mL]) as an internal standard, calibratIon curves for Topiramate were linear over a range of 1 to 30 µg/mL in human plasma and were highly reliable (r2 = 0.9991). The lower limit of quantitatIon of the assay was 2 µg/mL in human plasma. PrecisIon (%CV <15%) and accuracy (<20%) for both intra- and inter-day validatIons were satisfactory. The method has been used in clinical pharmacology research. Copyright © 2001 John Wiley & Sons, Ltd.
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Rapid approach to the quantitative determinatIon of Topiramate (2,3:4,5-bis-O-(1-methylethylidene)-β-D-fructopyranose sulfamate) in human plasma by liquid–liquid extractIon and flow-injectIon Negative-Ion Electrospray mass spectrometry
Rapid Communications in Mass Spectrometry, 1999Co-Authors: Su Chen, Paul M. CarveyAbstract:Topiramate, a sulfamate-substituted monosaccharide (2,3:4,5-bis-O-(1-methylethylidene)-β-D-fructopyranose sulfamate), is a new antiepileptic drug, which has been approved for adjunctive therapy in adult patients with partial-onset seizures. Liquid-liquid extractIon followed by flow-injectIon Negative-Ion Electrospray mass spectrometry was evaluated as a means for the quantitative analysis of Topiramate in human plasma. Prednisone (1,4-pregnadiene-17-α,21-diol-3,11,20-trIone [15 µg/mL]) was used as the internal standard because its solubility and molecular weight are similar to those of Topiramate. CalibratIon curves for Topiramate were linear over a range of 1 to 30 µg/mL plasma (signal-to-noise ratio >4) and were highly reliable (r2 = 0.994). This approach offers several advantages: (i) the extractIon of Topiramate from human plasma using chloroform is simple and reproducible; (ii) the quantitative determinatIon of Topiramate, in the presence of an internal standard, by flow-injectIon Negative-Ion Electrospray mass spectrometry with selected-Ion recording, is rapid and accurate and does not require chromatographic separatIon; (iii) the assay possesses adequate sensitivity (2–25 µg/mL) for the quantitative analysis of Topiramate in plasma from patients. Copyright © 1999 John Wiley & Sons, Ltd.
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rapid approach to the quantitative determinatIon of topiramate 2 3 4 5 bis o 1 methylethylidene β d fructopyranose sulfamate in human plasma by liquid liquid extractIon and flow injectIon Negative Ion Electrospray mass spectrometry
Rapid Communications in Mass Spectrometry, 1999Co-Authors: Su Chen, Paul M. CarveyAbstract:Topiramate, a sulfamate-substituted monosaccharide (2,3:4,5-bis-O-(1-methylethylidene)-β-D-fructopyranose sulfamate), is a new antiepileptic drug, which has been approved for adjunctive therapy in adult patients with partial-onset seizures. Liquid-liquid extractIon followed by flow-injectIon Negative-Ion Electrospray mass spectrometry was evaluated as a means for the quantitative analysis of Topiramate in human plasma. Prednisone (1,4-pregnadiene-17-α,21-diol-3,11,20-trIone [15 µg/mL]) was used as the internal standard because its solubility and molecular weight are similar to those of Topiramate. CalibratIon curves for Topiramate were linear over a range of 1 to 30 µg/mL plasma (signal-to-noise ratio >4) and were highly reliable (r2 = 0.994). This approach offers several advantages: (i) the extractIon of Topiramate from human plasma using chloroform is simple and reproducible; (ii) the quantitative determinatIon of Topiramate, in the presence of an internal standard, by flow-injectIon Negative-Ion Electrospray mass spectrometry with selected-Ion recording, is rapid and accurate and does not require chromatographic separatIon; (iii) the assay possesses adequate sensitivity (2–25 µg/mL) for the quantitative analysis of Topiramate in plasma from patients. Copyright © 1999 John Wiley & Sons, Ltd.
Alan G Marshall - One of the best experts on this subject based on the ideXlab platform.
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characterizatIon of pine pellet and peanut hull pyrolysis bio oils by Negative Ion Electrospray IonizatIon fourier transform Ion cyclotron resonance mass spectrometry
Energy & Fuels, 2012Co-Authors: Jacqueline M Jarvis, Ryan P Rodgers, Amy M Mckenna, Roger N Hilten, Alan G MarshallAbstract:Pyrolysis of solid biomass, in this case pine pellets and peanut hulls, generates a hydrocarbon-rich liquid product (bio-oil) consisting of oily and aqueous phases. Here, each phase is characterized by Negative-Ion Electrospray IonizatIon Fourier transform Ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) to yield unique elemental compositIons for thousands of compounds. Bio-oils are dominated by Ox species: few oxygens per molecule for the oily phase and many more oxygens per molecules for the aqueous phase. Thus, the increased oxygen content per molecule accounts for its water solubility. Peanut hull bio-oil is much more compositIonally complex and contains more nitrogen-containing compounds than pine pellet bio-oil. Bulk C, H, N, O, and S measurements confirm the increased levels of nitrogen-containing species identified in the peanut hull pyrolysis oil by FT-ICR MS. The ability of FT-ICR MS to identify and assign unique elemental compositIons to compositIonally complex bio-oils based on ultrah...
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effect of thermal treatment on acidic organic species from athabasca bitumen heavy vacuum gas oil analyzed by Negative Ion Electrospray fourier transform Ion cyclotron resonance ft icr mass spectrometry
Energy & Fuels, 2009Co-Authors: Donald F Smith, Ryan P Rodgers, Parviz Rahimi, Alem Teclemariam, Alan G MarshallAbstract:We examine suspected molecular transformatIons of thermally treated Athabasca bitumen heavy vacuum gas oil (HVGO) by ultrahigh-resolutIon Negative-Ion Electrospray IonizatIon Fourier transform Ion cyclotron resonance mass spectrometry. Liquid products from HVGOs treated under an inert N2 atmosphere at temperatures of 300, 325, 350, and 400 °C were each characterized by class (heteroatom content), type (double-bond equivalents = number of rings plus double bonds to carbon), and carbon number distributIon. In additIon, the inert N2 sweep gas of the autoclave was collected, condensed, and analyzed. The total acid number (TAN) of the HVGO liquid products decreases with an increasing treatment temperature (from 4.13 at 300 °C to 1.46 at 400 °C), indicative of potential carboxylic acid decompositIon. The highly abundant O2 class contains species with DBE = 3; however, no compositIonal changes occur with increased treatment temperature. A bimodal DBE distributIon is observed for the S1O2 class, suggesting two po...
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identificatIon of acidic nso compounds in crude oils of different geochemical origins by Negative Ion Electrospray fourier transform Ion cyclotron resonance mass spectrometry
Organic Geochemistry, 2002Co-Authors: Christine A Hughey, Ryan P Rodgers, Alan G Marshall, Kuangnan Qian, Winston K RobbinsAbstract:Abstract We present the selective IonizatIon, resolutIon and identificatIon of acidic NSO compounds in three crude oils of different geochemical origins by Negative Ion Electrospray IonizatIon (ESI) Fourier transform Ion cyclotron resonance mass spectrometry (FT-ICR MS). Selective IonizatIon by ESI affords direct detectIon of neutral nitrogen compounds and carboxylic acids in petroleum without pre-chromatographic isolatIon. Ultra-high resolutIon/mass accuracy allows detailed and positive identificatIon of acidic NSO compounds in the crude oils. Observed compositIonal differences reflect known crude oil properties/histories. Collectively, ∼14,000 masses, spanning 18 different heteroatomic classes, are identified unequivocally, demonstrating the potential of ESI-FT-ICR MS for geochemical applicatIons.
Richard B. Cole - One of the best experts on this subject based on the ideXlab platform.
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“Best Match” Model and Effect of Na+/H+ Exchange on AnIon Attachment to Peptides and Stability of Formed Adducts in Negative Ion Electrospray Mass Spectrometry
Journal of The American Society for Mass Spectrometry, 2013Co-Authors: Xiaohua Liu, Richard B. ColeAbstract:The “Best Match” model has been extended to account for the role that Na+/H+ exchange plays on anIon attachment in Negative Ion Electrospray. Without any Na+/H+ exchange on (Glu) fibrinopeptide B, the higher basicity anIons F− and CH3COO− can hardly form observable adducts; however, after multiple Na+/H+ exchanges, adduct formatIon is enabled. Moreover, dissociatIon pathways of CF3COO− adducts with singly deprotonated peptides that have undergone 0 to 3 Na+/H+ exchanges exhibit a shift in CID product Ions from losing predominately CF3COOH (case of 0 Na+/H+ exchanges) to losing predominately CF3COO− (case of 3 Na+/H+ exchanges). These phenomena can be ratIonalized by considering that Na+ catIons exchange at, and serve to “block”, the most acidic sites, thereby forcing implicated anIons to attach to lower acidity protons. In additIon to forming Ion pairs with carboxylate groups, Na+ also participates in formatIon of tri-atomic Ions of the form ANaA− during adduct dissociatIon. The fact that low gas-phase basicity (GB) anIons preferentially form ANaA− species, even though high GB anIons form more stable tri-atomic species, indicates that the monatomic Ions were not in close contact in the initial adduct. The propensity for formatIon of stable anIonic adducts is dependent on the degree of matching between anIon GBs and GBapp of deprotonated sites on the peptide. The GBapp is raised dramatically as the charge state of the peptide increases via a through-space effect. The presence of Na+ on carboxylate sites substantially decreases the GBapp by neutralizing these sites, while slightly increasing the intrinsic GBs by an inductive effect.
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characterizatIon of an exceptIon to the even electron rule upon low energy collisIon induced decompositIon in Negative Ion Electrospray tandem mass spectrometry
Journal of Mass Spectrometry, 2010Co-Authors: Zhenzhen Mo, Nalaka S Rannulu, Bing Guan, Srinivasan Kannupal, Bruce C Gibb, Richard B. ColeAbstract:Electrospray-generated precursor Ions usually follow the ‘even-electron rule’ and yield ‘closed shell’ fragment Ions. We characterize an exceptIon to the ‘even-electron rule.’ In Negative Ion Electrospray mass spectrometry (ES-MS), 2-(ethoxymethoxy)-3-hydroxyphenol (2-hydroxyl protected pyrogallol) easily formed a deprotonated molecular Ion (M-H)− at m/z 183. Upon low-energy collisIon induced decompositIon (CID), the m/z 183 precursor yielded a radical Ion at m/z 124 as the base peak. The radical anIon at m/z 124 was still the major fragment at all tested collisIon energies between 0 and 50 eV (Elab). Supported by computatIonal studies, the appearance of the radical anIon at m/z 124 as the major product Ion can be attributed to the combinatIon of a low reverse activatIon barrier and resonance stabilizatIon of the product Ions. Furthermore, our data lead to the proposal of a novel alternative radical formatIon pathway in the protectIon group removal of pyrogallol. Copyright © 2009 John Wiley & Sons, Ltd.
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StabilizatIon of anIonic adducts in Negative Ion Electrospray mass spectrometry.
Analytical Chemistry, 2002Co-Authors: Yang Cai, Richard B. ColeAbstract:Attachment of small anIons to neutral molecules is an important IonizatIon mechanism in Negative Ion Electrospray mass spectrometry. In this report, the tendency for different anIons to remain attached to selected analyte compound classes has been systematically investigated. A ratIonale for the formatIon and stability of preferred anIonic adducts is proposed in light of thermodynamic consideratIons. A series of collisIon-induced dissociatIon experiments reveals that the gas-phase basicities of the deprotonated analyte molecule ([M − H]-) and the anIon moiety play important roles in determining the stability of anIonic adducts. Adducts of the form [M − H]-···H+···[anIon]- manifest increased stability when the two anIons have similar gas-phase basicities. Within certain limitatIons, the difference in ΔG° values for proton combinatIon with [M − H]- and with [anIon]- can be used as a first-order predictor of adduct stability. In additIon, stability increases with the rising gas-phase basicities of the two mo...
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Ranking of gas-phase acidities and chloride affinities of monosaccharides and linkage specificity in collisIon-induced decompositIons of Negative Ion Electrospray-generated chloride adducts of oligosaccharides
Journal of the American Society for Mass Spectrometry, 2001Co-Authors: Junhua Zhu, Richard B. ColeAbstract:Negative Ion Electrospray-tandem mass spectrometry has been employed to study chloride adducts of saccharide molecules. DecompositIons of [M + Cl]^− obtained under identical low-energy collisIon conditIons allow the approximate ranking of chloride affinities and gas-phase acidities of a series of isomeric monosaccharides. The ketohexoses are found to be more acidic than the aldohexoses. Chloride adduct decompositIons are examined for a glucopyranosyl fructose and a glucopyranosyl glucose series. For each disaccharide series, the linkage positIon is shown to markedly influence the favored pathways of [M + Cl]^− decompositIons, initiated either by loss of neutral HCl to form [M − H]^− and possibly leading to further (consecutive) decompositIons, or by loss of M to form Cl^−. Upon formatIon of [M − H]^−, both cross-ring cleavages and glycosidic bond decompositIons were observed in varying degrees for the two series of disaccharides. Remarkably, for three non-reducing polysaccharides that each contain a terminal sucrose group at the “downstream” end, chlorine-containing product Ions arising from cleavage of the Glcα−2Fru linkage have been observed. Apart from Cl^−, chlorine-containing product Ions are not observed for any of the other disaccharides investigated, and they appear to be specifically diagnostic of a terminal Glcα-2Fru linkage. Their appearance is ratIonalized based upon a substantially reduced tendency for HCl loss from these non-reducing polysaccharides.
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FormatIon and decompositIons of chloride adduct Ions, [M + Cl]^−, in Negative Ion Electrospray IonizatIon mass spectrometry
Journal of the American Society for Mass Spectrometry, 2000Co-Authors: Junhua Zhu, Richard B. ColeAbstract:The ability to promote chloride-attachment Ions of the form [M + Cl]^− in Negative Ion Electrospray IonizatIon mass spectrometry (ESI-MS) has been developed using chlorinated solvents such as chloroform and carbon tetrachloride. This approach expands the current capabilities of Negative Ion ESI-MS by enabling detectIon of analytes that lack acidic sites and thus exhibit weak [M − H]^− signals. In contrast to the remote-site collisIon-induced dissociatIon (CID) often observed in positive Ion ESI-MS/MS for alkali metal catIon adducts, the decompositIon of chloride adducts usually proceeds via competitive dissociatIons to form Cl^−, which is not structurally informative, or [M − H]^−. The latter can provide structural informatIon via consecutive decompositIons. For compounds having higher gas-phase acidities than HCl, a low CID collisIon energy can promote the formatIon of [M − H]^−, whereas for the majority of compounds with lower gas phase acidities than HCl, higher collisIon energies generally improve the relative yield of [M − H]^−. Because chloride attachment occurs primarily at electrophilic hydrogens, the daughter Ion ratio, Cl^−/[M − H]^−, depends primarily upon the difference in gas phase acidity between the analyte molecule and HCl. At higher collisIon energies, entropic factors take on increased importance in determining the product ratio. The difference between the Δ S ^0 terms for formatIon of Cl^− and formatIon of [M − H]− has been estimated for a series of substituted phenols and a series of acetic acid analogs. Finally, a novel neutral loss of CH_3Cl from glycerophosphocholine and from ganglioside GM3 methyl ester is reported.
