Showing papers on "Electrospray ionization published in 2012"
TL;DR: The present review has described the development of Electrospray Ionization mass spectrometry (ESI-MS) during the last 25 years in the study of various properties of different types of biological molecules.
Abstract: The Electrospray Ionization (ESI) is a soft ionization technique extensively used for production of gas phase ions (without fragmentation) of thermally labile large supramolecules. In the present review we have described the development of Electrospray Ionization mass spectrometry (ESI-MS) during the last 25 years in the study of various properties of different types of biological molecules. There have been extensive studies on the mechanism of formation of charged gaseous species by the ESI. Several groups have investigated the origin and implications of the multiple charge states of proteins observed in the ESI-mass spectra of the proteins. The charged analytes produced by ESI can be fragmented by activating them in the gas-phase, and thus tandem mass spectrometry has been developed, which provides very important insights on the structural properties of the molecule. The review will highlight recent developments and emerging directions in this fascinating area of research.
519 citations
TL;DR: It could be shown that a dilution of extracts by a factor of 25-40 reduces ion suppression to less than 20% if the initial suppression is ≤80%, and for stronger matrix effects or complete elimination of suppression, higher dilution factors were needed.
Abstract: In this study, the relationship between matrix concentration and suppression of electrospray ionization (matrix effects) was investigated. Ion suppression of pesticides present in QuEChERS extracts was used as an example. Residue-free extracts of four different commodities, avocado, black tea, orange, and rocket (arugula), were fortified with 39 pesticides each. For many of the resulting 156 pesticide/matrix combinations, considerable matrix effects were observed if the coextracted matrix of 8 mg of equivalent sample (in the case of tea: 1.6 mg) was injected with the undiluted extracts. The reduction of these matrix effects was measured at 10 levels of dilution up to 1000-fold. The results obtained indicate a linear correlation between matrix effects and the logarithm of matrix concentration (or dilution factor) until the zero-effect level of further dilution was reached. Using the logarithmic equations, it could be shown that a dilution of extracts by a factor of 25–40 reduces ion suppression to less tha...
276 citations
TL;DR: A method using reversed-phase ultra high performance liquid chromatography (UPLC) coupled with electrospray ionization tandem mass spectrometry (ESI/MSMS) to simultaneously quantify 28 urinary VOC metabolites as biomarkers of exposure is developed.
208 citations
TL;DR: The implementation of the direct ESI-MS assay for the determination of protein–ligand binding stoichiometry and affinity is described and common sources of error encountered with these measurements are outlined.
197 citations
TL;DR: The elemental compositions deduced from the UHRMS analysis confirm the conclusion from the previous study that biomass burning and SOA formation are both important sources of HULIS in the PRD region.
Abstract: The HUmic-LIke Substances (HULIS) fraction isolated from aerosol samples collected at a rural location of the Pearl River Delta Region (PRD), China, during the harvest season was analyzed by both positive and negative mode electrospray ionization (ESI) coupled with an ultrahigh resolution mass spectrometer (UHRMS). With the remarkable resolving power and mass accuracy of ESI-UHRMS, thousands of elemental formulas were identified. Formulas detected in the positive (ESI+) and the negative (ESI-) mode complement each other due to differences in the ionization mechanism, and the use of both provides a more complete characterization of HULIS. Compounds composed of C, H, and O atoms were preferentially detected in ESI- by deprotonation, implying their acidic properties. Tandem MS and Kendrick Mass Defect analysis implies that carboxyl groups are abundant in the CHO compounds. This feature is similar to those of natural fulvic acids, but relatively smaller molecular weights are observed in the HULIS samples. A g...
188 citations
TL;DR: Single crystal X-ray crystallography and electrospray ionization mass spectrometry (ESI-MS) unequivocally determined the cluster formula to be [Au(24)(PPh(3))(10)(SC(2)H(4)Ph)(5)X(2)](+), where X = Cl and/or Br.
Abstract: We report the synthesis and total structure determination of a Au(24) nanocluster protected by mixed ligands of phosphine and thiolate. Single crystal X-ray crystallography and electrospray ionization mass spectrometry (ESI-MS) unequivocally determined the cluster formula to be [Au(24)(PPh(3))(10)(SC(2)H(4)Ph)(5)X(2)](+), where X = Cl and/or Br. The structure consists of two incomplete (i.e., one vertex missing) icosahedral Au(12) units joined by five thiolate linkages. This structure shows interesting differences from the previously reported vertex-sharing biicosahedral [Au(25)(PPh(3))(10)(SC(2)H(4)Ph)(5)X(2)](2+) nanocluster protected by the same type and number of phosphine and thiolate ligands. The optical absorption spectrum of Au(24) nanocluster was theoretically reproduced and interpreted.
176 citations
TL;DR: An LC-MS based method for the profiling and characterization of ceramide species in the upper layer of human skin resulted in an accurate mass retention time library for targeted profiling of skin ceramides and demonstrated that targeted data processing results in an improved repeatability versus untargeted data processing.
Abstract: An LC-MS based method for the profiling and characterization of ceramide species in the upper layer of human skin is described. Ceramide samples, collected by tape stripping of human skin, were analyzed by reversed-phase liquid chromatography coupled to high-resolution quadrupole time-of-flight mass spectrometry operated in both positive and negative electrospray ionization mode. All known classes of ceramides could be measured in a repeatable manner. Furthermore, the data set showed several undiscovered ceramides, including a class with four hydroxyl functionalities in its sphingoid base. High-resolution MS/MS fragmentation spectra revealed that each identified ceramide species is composed of several skeletal isomers due to variation in carbon length of the respective sphingoid bases and fatty acyl building blocks. The resulting variety in skeletal isomers has not been previously demonstrated. It is estimated that over 1000 unique ceramide structures could be elucidated in human stratum corneum. Ceramide species with an even and odd number of carbon atoms in both chains were detected in all ceramide classes. Acid hydrolysis of the ceramides, followed by LC-MS analysis of the end-products, confirmed the observed distribution of both sphingoid bases and fatty acyl groups in skin ceramides. The study resulted in an accurate mass retention time library for targeted profiling of skin ceramides. It is furthermore demonstrated that targeted data processing results in an improved repeatability versus untargeted data processing (72.92% versus 62.12% of species display an RSD < 15%).
165 citations
TL;DR: Recently researchers have established direct linkages between gas-phase data obtained via ESI-MS and processes occurring in solution, and these results reveal qualitative and quantitative correlations between E SI-MS measurements and solution properties.
Abstract: Mechanistic studies form the basis for a better understanding of chemical processes, helping researchers develop more sustainable reactions by increasing the yields of the desired products, reducing waste production, and lowering the consumption of resources and energy overall. Conventional methods for the investigation of reaction mechanisms in solution include kinetic studies, isotope labeling, trapping of reactive intermediates, and advanced spectroscopic techniques. Within the past decade, electrospray ionization mass spectrometry (ESI-MS) has provided an additional tool for mechanistic studies because researchers can directly probe liquid samples by mass spectrometry under gentle conditions.Specifically, ESI-MS allows researchers to identify the molecular entities present in solution over the course of a chemical transformation. ESI-MS is particularly useful for investigations of organic reactions or metal catalysis that involve ionic intermediates. Accordingly, researchers are increasingly using ESI...
163 citations
TL;DR: Optimization of experimental parameters including emitter capillary size, solvent composition, solvent flow rate, mass spectrometry scan-rate and step-size is shown here to improve the resolution available in the study of biological tissue from 180 μm to about 35 μm using an unmodified commercial mass Spectrometer.
Abstract: Desorption electrospray ionization imaging allows biomarker discovery and disease diagnosis through chemical characterization of biological samples in their native environment. Optimization of experimental parameters including emitter capillary size, solvent composition, solvent flow rate, mass spectrometry scan-rate and step-size is shown here to improve the resolution available in the study of biological tissue from 180 μm to about 35 μm using an unmodified commercial mass spectrometer. Mouse brain tissue was used to optimize and measure resolution based on known morphological features and their known relationships to major phospholipid components. Features of approximately 35 μm were resolved and correlations drawn between features in grey matter (principally PS (18:0/22:6), m/z 834) and in white matter (principally ST (24:1), m/z 888). The improved spatial resolution allowed characterization of the temporal changes in lipid profiles occurring within mouse ovaries during the ovulatory cycle. An increase in the production of phosphatidylinositol (PI 38:4) m/z 885 and associated fatty acids such as arachidonic acid (FA 20:4) m/z 303 and adrenic acid (FA 22:4) m/z 331was seen with the postovulatory formation of the corpus luteum.
139 citations
TL;DR: Study shows that supported Ag and Au NPs may be employed in sustainable environmental remediation, as they can be used at room temperature in aqueous solutions without the use of additional stimulus such as UV light.
Abstract: Application of nanoparticles (NPs) in environmental remediation such as water purification requires a detailed understanding of the mechanistic aspects of the interaction between the species involved. Here, an attempt was made to understand the chemistry of noble metal nanoparticle–pesticide interaction, as these nanosystems are being used extensively for water purification. Our model pesticide, chlorpyrifos (CP), belonging to the organophosphorothioate group, is shown to decompose to 3,5,6-trichloro-2-pyridinol (TCP) and diethyl thiophosphate at room temperature over Ag and Au NPs, in supported and unsupported forms. The degradation products were characterized by absorption spectroscopy and electrospray ionization mass spectrometry (ESI MS). These were further confirmed by ESI tandem mass spectrometry. The interaction of CP with NP surfaces was investigated using transmission electron microscopy, energy dispersive analysis of X-rays, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). XPS rev...
136 citations
TL;DR: Polyphenol profile of Citrus juices of sweet orange, tangerine, lemon and grapefruit from Spanish cultivars was obtained by High-Performance Liquid Chromatography with Diode Array Detection coupled to Electrospray ionization and Triple Quadrupole Mass Spectrometry.
TL;DR: A new method for the nontargeted quantitation of polar lipid classes separated by hydrophilic interaction liquid chromatography (HILIC) followed by positive-ion electrospray ionization mass spectrometry (ESI-MS) using a single internal lipid standard to which all class specific response factors (RFs) are related to.
Abstract: The identification and quantitation of a wide range of lipids in complex biological samples is an essential requirement for the lipidomic studies. High-performance liquid chromatography–mass spectrometry (HPLC/MS) has the highest potential to obtain detailed information on the whole lipidome, but the reliable quantitation of multiple lipid classes is still a challenging task. In this work, we describe a new method for the nontargeted quantitation of polar lipid classes separated by hydrophilic interaction liquid chromatography (HILIC) followed by positive-ion electrospray ionization mass spectrometry (ESI-MS) using a single internal lipid standard to which all class specific response factors (RFs) are related to. The developed method enables the nontargeted quantitation of lipid classes and molecules inside these classes in contrast to the conventional targeted quantitation, which is based on predefined selected reaction monitoring (SRM) transitions for selected lipids only. In the nontargeted quantitatio...
TL;DR: It is demonstrated that n-octylethyl ammonium hexafluorophosphate (G) can thread through the cavity of 1,4-dimethoxypillar[5]arene to form a [2]pseudorotaxane with a binding constant of 1.09 (±0.31) × 10(3) M(-1) in chloroform.
TL;DR: A solid phase microextraction, multistep elution, transient isotachophoresis (tITP) capillary electrophoresis-tandem mass spectrometry (CE-MS/MS) procedure which employs a high sensitivity porous electrospray ionization (ESI) sprayer for the proteomic analysis of a moderately complex protein mixture is described.
Abstract: We describe a solid phase microextraction (SPME), multistep elution, transient isotachophoresis (tITP) capillary electrophoresis–tandem mass spectrometry (CE–MS/MS) procedure which employs a high sensitivity porous electrospray ionization (ESI) sprayer for the proteomic analysis of a moderately complex protein mixture. In order to improve comprehensiveness and sensitivity over a previously reported proteomic application of the ESI sprayer, we evaluated preconcentration with SPME and multistep elution prior to tITP stacking and CE separation. To maximize separation efficiency, we primarily employed electrokinetic methods for elution and separation after loading the sample by application of pressure. Conditions were developed for optimum simultaneous electrokinetic elution and sample stacking using a tryptic digest of 16 proteins to maximize peptide identifications and minimize band broadening. We performed comparative proteomic analysis of a dilution series using CE and nanoflow liquid chromatography (nLC)...
TL;DR: How conjunction of mass spectrometry with related techniques and methodologies such as ion mobility, hydrogen-deuterium exchange (HDX), protein footprinting or chemical cross-linking can provide us with structural information useful for drug development is discussed.
Abstract: The initial stages of drug discovery are increasingly reliant on development and improvement of analytical methods to investigate protein–protein and protein–ligand interactions. For over 20 years, mass spectrometry (MS) has been recognized as providing a fast, sensitive and high-throughput methodology for analysis of weak non-covalent complexes. Careful control of electrospray ionization conditions has enabled investigation of the structure, stability and interactions of proteins and peptides in a solvent free environment. This critical review covers the use of mass spectrometry for kinetic, dynamic and structural studies of proteins and protein complexes. We discuss how conjunction of mass spectrometry with related techniques and methodologies such as ion mobility, hydrogen–deuterium exchange (HDX), protein footprinting or chemical cross-linking can provide us with structural information useful for drug development. Along with other biophysical techniques, such as NMR or X-ray crystallography, mass spectrometry provides a powerful toolbox for investigation of biological problems of medical relevance (204 references).
TL;DR: The results have successfully demonstrated the capability of selective and quantitative analysis of cell-based drug absorption and metabolites with high stability, sensitivity, and repeatability on the chip-ESI-MS system.
Abstract: In this work, a stable isotope labeling assisted microfluidic chip electrospray ionization mass spectrometry (SIL-chip–ESI-MS) platform for qualitative and quantitative analysis of cell metabolism was developed. Microfluidic cell culture, drug-induced cell apoptosis analysis, and cell metabolism measurements were performed simultaneously on the specifically designed device. MCF-7 cells were cultivated in vitro and exposed in anticancer agent (genistein and genistein-d2) for cell-based drug assay. A dual-isotopic labeling was presented for effective qualitative analysis of multiplex metabolites. Interestingly, three coeluting pairs of isotopomers appeared with an m/z difference of two. Despite complex biological matrixes, they can be easily recognized and identified by chip–ESI-MS/MS, which significantly facilitates candidate biomarker discovery. The quantitative performance of this system was evaluated using genistein as a model drug by means of stable isotope dilution analysis. The linear equation obtain...
TL;DR: Overall, the UHPLC/ESI Q-Orbitrap has demonstrated great performance for quantification and confirmation of pesticide residues in fresh fruits and vegetables.
Abstract: This paper presents an application of ultrahigh-performance liquid chromatography and electrospray ionization quadrupole Orbitrap high-resolution mass spectrometry (UHPLC/ESI Q-Orbitrap) for determination of 166 pesticide residues in fruits and vegetables. Pesticides were extracted from the samples using the QuEChERS (quick, easy, cheap, effective, rugged, and safe) procedure. UHPLC/ESI Q-Orbitrap MS (i.e., full MS scan) acquired full MS data for quantification, and UHPLC/ESI Q-Orbitrap dd-MS2 (i.e., data-dependent scan) obtained product-ion spectra for confirmation. UHPLC/ESI Q-Orbitrap MS quantification was achieved using matrix-matched standard calibration curves with isotopically labeled standards or chemical analogues as internal standards. The method performance characteristics that included overall recovery, intermediate precision, and measurement uncertainty were evaluated according to a nested experimental design. For the matrices studied, about 90.3–91.5% of the pesticides had recoveries between...
TL;DR: This approach identified more than twice as many proteins as the previous record for capillary electrophoresis proteome analysis, suggesting CE-ESI-MS/MS is a useful tool for the analysis of proteome samples of intermediate complexity.
Abstract: We demonstrate the use of capillary zone electrophoresis with an electrokinetically pumped sheath-flow electrospray interface for the analysis of a tryptic digest of a sample of intermediate protein complexity, the secreted protein fraction of Mycobacterium marinum. For electrophoretic analysis, 11 fractions were generated from the sample using reverse-phase liquid chromatography; each fraction was analyzed by CZE-ESI-MS/MS, and 334 peptides corresponding to 140 proteins were identified in 165 min of mass spectrometer time at 95% confidence (FDR < 0.15%). In comparison, 388 peptides corresponding to 134 proteins were identified in 180 min of mass spectrometer time by triplicate UPLC-ESI-MS/MS analyses, each using 250 ng of the unfractionated peptide mixture, at 95% confidence (FDR < 0.15%). Overall, 62% of peptides identified in CZE-ESI-MS/MS and 67% in UPLC-ESI-MS/MS were unique. CZE-ESI-MS/MS favored basic and hydrophilic peptides with low molecular masses. Combining the two data sets increased the number of unique peptides by 53%. Our approach identified more than twice as many proteins as the previous record for capillary electrophoresis proteome analysis. CE-ESI-MS/MS is a useful tool for the analysis of proteome samples of intermediate complexity.
TL;DR: For the first time, a mixed-mode solid-phase extraction with fractionation of basic analytes from neutral and acidic species during cartridge elution and liquid chromatography-quadrupole-time-of-flight mass spectrometry was combined for the quantitative determination of 24 illicit drugs and metabolites in urban sewage samples.
Abstract: For the first time, a mixed-mode solid-phase extraction with fractionation of basic analytes from neutral and acidic species during cartridge elution and liquid chromatography–quadrupole-time-of-flight mass spectrometry (LC–QTOF-MS) was combined for the quantitative determination of 24 illicit drugs and metabolites in urban sewage samples. The effects of several sample preparation and instrumental parameters in the sensitivity and selectivity of the quantitative method are thoroughly discussed. Under final working conditions, recoveries above 63% and 82% were attained for all species in raw and treated sewage, respectively; whereas, the limits of quantification of the method, defined for a signal-to-noise of 10 (S/N = 10), ranged from 2 to 50 ng L–1. Sequential elution of mixed-mode cartridges allowed a significant reduction of matrix effects observed during electrospray ionization of basic drugs versus those measured for hydrophilic balance reversed-phase sorbents and the same mixed-mode polymer without ...
TL;DR: Phenolic acids and flavonol O-glycosides were extracted from the peels of jocote fruits (Spondias purpurea L., Anacardiaceae) harvested in Costa Rica and characterized using ultra highperformance liquid chromatography coupled with diode array and electrospray ionization mass spectrometric detection (UHPLC-DAD-ESI-MSn).
TL;DR: The procedure of sample preparation and LC-QTOF-MS analysis proved to be a robust and sensitive routine method in which the qualitative screening for a wide variety of toxic substances in hair is combined with the quantitative determination of selected illegal drugs.
TL;DR: This work presents optimized electrospray ionization mass spectrometry (ESI-MS) instrumental parameters for the maximal transmission of the intact cluster and makes the first formula assignment for a ligand-protected Ag cluster of Ag(32)(SG)(19).
Abstract: Mass spectrometry has played a key role in identifying the members of a series of gold clusters, which has enabled the development of magic-number cluster theory. The successes of the gold cluster system have yet to be repeated in another metal cluster system, however. Silver clusters in particular have proven to be challenging due to their relative instability compared with gold clusters. Using the well-characterized gold nanocluster, Au25(SG)18, we present optimized electrospray ionization mass spectrometry (ESI-MS) instrumental parameters for the maximal transmission of the intact cluster. Parameters shown to have the largest effect on intact cluster transmission/detection include trap and transfer collision energy, source temperature, and cone gas flow rate. Herein we describe a general strategy to acquire mass spectra of fragile metal clusters with reliable mass assignments. By also optimizing sample solution conditions, high-quality ESI mass spectra of a prototypical silver:glutathione (Ag:SG) clust...
TL;DR: In this paper, the authors present a review of CE-ESI-MS interfaces, including their major advantages, drawbacks, and fields of application, and discuss the electrochemical reactions involved in the ESI and CE processes.
TL;DR: The SPE-LC/tqMS method was successfully applied to quantify 13 HAcAms in drinking water samples for the first time, and first indentified tribromo acetamide and chloroiodoacetamide as DBPs in drinkingWater.
TL;DR: A red pine fast pyrolysis bio-oil was subjected to sequential solvent fractionation into n-hexane soluble (HS), ether soluble (ES), ether insoluble (EIS), dichloromethane solvers (DS), and methanol soluble (MeS) fractions, which indicated the presence of acids, aldehydes, ketones, alcohols, phenols, and anhydromonosaccharides.
Abstract: A red pine fast pyrolysis bio-oil was subjected to sequential solvent fractionation into n-hexane soluble (HS), ether soluble (ES), ether insoluble (EIS), dichloromethane soluble (DS), and methanol soluble (MeS) fractions. The volatile components of bio-oil were analyzed by gas chromatography–mass spectrometry (GC–MS), indicating the presence of acids, aldehydes, ketones, alcohols, phenols, and anhydromonosaccharides, which consisted of methoxy, hydroxy, and carbonyl functional groups. These results imply that the bio-oil was similar to the most reported fast pyrolysis bio-oil samples in molecular composition. The bio-oil and its five subfractions were analyzed by negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The predominant compounds in bio-oil were O2–O17 class species with 1–22 double-bond equivalent (DBE) values and 4–39 carbon numbers. The most abundant class species in biocrude oil, HS, ES, EIS, DS, and MeS subfractions were O7, O...
TL;DR: The annotation of the human adult urinary metabolome and metabolite identification from electrospray ionization mass spectrometry (ESI-MS)-based metabolomics data sets and features of biological interest are annotated.
Abstract: Metabolic profiles of biofluids obtained by atmospheric pressure ionization mass spectrometry-based technologies contain hundreds to thousands of features, most of them remaining unknown or at least not characterized in analytical systems. We report here on the annotation of the human adult urinary metabolome and metabolite identification from electrospray ionization mass spectrometry (ESI-MS)-based metabolomics data sets. Features of biological interest were first of all annotated using the ESI-MS database of the laboratory. They were also grouped, thanks to software tools, and annotated using public databases. Metabolite identification was achieved using two complementary approaches: (i) formal identification by matching chromatographic retention times, mass spectra, and also product ion spectra (if required) of metabolites to be characterized in biological data sets to those of reference compounds and (ii) putative identification from biological data thanks to MS/MS experiments for metabolites not available in our chemical library. By these means, 384 metabolites corresponding to 1484 annotated features (659 in negative ion mode and 825 in positive ion mode) were characterized in human urine samples. Of these metabolites, 192 and 66 were formally and putatively identified, respectively, and 54 are reported in human urine for the first time. These lists of features could be used by other laboratories to annotate their ESI-MS metabolomics data sets.
TL;DR: In this paper, negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) was used to yield unique elemental compositions for thousands of compounds.
Abstract: 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...
TL;DR: A simple and reliable HILIC-Fourier transform (FT)-ESI-MS platform to characterize and compare two currently marketed LMWH products using the top-down approach requiring no special sample preparation steps is presented.
Abstract: Low molecular heparins (LMWHs) are structurally complex, heterogeneous, polydisperse, and highly negatively charged mixtures of polysaccharides. The direct characterization of LMWH is a major challenge for currently available analytical technologies. Electrospray ionization (ESI) liquid chromatography-mass spectrometry (LC-MS) is a powerful tool for the characterization complex biological samples in the fields of proteomics, metabolomics, and glycomics. LC-MS has been applied to the analysis of heparin oligosaccharides, separated by size exclusion, reversed phase ion-pairing chromatography, and chip-based amide hydrophilic interaction chromatography (HILIC). However, there have been limited applications of ESI-LC-MS for the direct characterization of intact LMWHs (top-down analysis) due to their structural complexity, low ionization efficiency, and sulfate loss. Here we present a simple and reliable HILIC-Fourier transform (FT)-ESI-MS platform to characterize and compare two currently marketed LMWH products using the top-down approach requiring no special sample preparation steps. This HILIC system relies on cross-linked diol rather than amide chemistry, affording highly resolved chromatographic separations using a relatively high percentage of acetonitrile in the mobile phase, resulting in stable and high efficiency ionization. Bioinformatics software (GlycReSoft 1.0) was used to automatically assign structures within 5-ppm mass accuracy.
TL;DR: This study demonstrates the identification and separation of N- and O-protonated 4-ABA using DMS, with structural assignments verified by the presence of distinct peaks in the DMS ionogram.
Abstract: Here, we present the separation of two ions that differ only by the site of protonation of the analyte molecule using differential mobility spectrometry (DMS). Protonated 4-aminobenzoic acid molecules (4-ABA) generated by positive-mode electrospray ionization [ESI(+)] can exist with the proton residing on either the amine nitrogen (N-protonated) or the carboxylic acid oxygen (O-protonated), and the protonation site can differ on the basis of the solvent system used. In this study, we demonstrate the identification and separation of N- and O-protonated 4-ABA using DMS, with structural assignments verified by: (1) the presence of distinct peaks in the DMS ionogram, (2) the observed effects resulting from altering the ESI(+) solvent system, (3) the observed 13C NMR chemical shifts arising from altering the solvent system, (4) the observation of distinct MS/MS fragmentation patterns for the two DMS-separated ions, (5) the unique hydrogen–deuterium exchange behavior for these ions, and (6) the fundamental beha...
TL;DR: Mass spectrometric analysis of a banyan endophyte, Bacillus subtilis K1, extract revealed a complex mixture of lipopeptides, iturins, surfactins, and fengycins, where four major sites of heterogeneity are identified.