High Molecular Weight Ions Research Articles

A green and efficient synthetic strategy for the preparation of PBS ionomers with high molecular weight, high ionic group content and good combined properties

The conventional direct esterification and polycondensation is difficult to obtain kilogram scale of poly(butylene succinate) (PBS) ionomers with both high molecular weight and high ionic group content. Therefore, the investigation of relationship between the content of ion group and performance (such as mechanical properties) is impossible. In this work, the preparation of PBS ionomers with high molecular weight and high ion group content was achieved by transesterification method using sodium dimethyl isophthalate-5-sulfonate (SIPM) as the ionic monomer, and the polycondensation time decreased significantly with the increase of SIPM content. The mechanism of reducing the polycondensation time of PBS prepared by transesterification is proposed. The tensile strength, flexural strength and impact strength of PBS ionomers increased significantly with increasing SIPM content. At high ion group content, the formed multiplets-clusters among ion groups, which act as reversible physical crosslinking points and nano-fillers, substantially improved the mechanical properties. The tensile strength, flexural strength and impact strength improved and reached to 50.1 MPa, 40.9 MPa and 13.1 kJ/m2 at high ion group content from 34.2 MPa, 24.1 MPa and 5.8 kJ/m2 for PBS, respectively. It showed a totally opposite trend from the previous research. In addition, the hydrophilicity and processing properties of PBS ionomers improved significantly with the increase of the ion group content, and the contact angle reduced to 41.1° after the introduction of ions.

Chemical Composition of Gas-Phase Positive Ions during Laboratory Simulations of Titan’s Haze Formation

The organic haze in the atmosphere of Saturn’s moon Titan affects the moon’s atmospheric and surface properties. Ions are known to play an important role in haze formation chemistry; however, the role of ions in laboratory simulations of haze formation is poorly characterized. Here, we use a high-resolution time-of-flight mass spectrometer with an atmospheric pressure interface to chemically characterize the ambient gas-phase cations formed as haze is produced by the far ultraviolet photolysis of CH4 in N2. These experiments show that the chemical composition of the cations is complex. High molecular weight ions up to m/z 400 are observed, with organic nitrogen ions, including ions with multiple nitrogen atoms, accounting for the majority of the identified ion peaks. Many of the ions identified in this work have been observed in Titan’s upper atmosphere by the Cassini Ion and Neutral Mass Spectrometer. While the chemistry in this study is likely more representative of Titan’s lower atmosphere than of its ...

Imaging Mass Spectrometry of Endogenous Polypeptides and Secondary Metabolites from Galls Induced by Root-Knot Nematodes in Tomato Roots.

Nematodes are devastating pests that infect most cultivated plant species and cause considerable agricultural losses worldwide. The understanding of metabolic adjustments induced during plant-nematode interaction is crucial to generate resistant plants or to select more efficient molecules to fight against this pest. Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) has been used herein for in situ detection and mapping endogenous polypeptides and secondary metabolites from nematode-induced gall tissue. One of the major critical features of this technique is sample preparation; mainly, the generation of intact sections of plant cells with their rigid cell walls and vacuolated cytoplasm. Our experimental settings allowed us to obtain sections without contamination of exogenous ions or diffusion of molecules and to map the differential presence of low and high molecular weight ions in uninfected roots compared with nematode-induced galls. We predict the presence of lipids in both uninfected roots and galls, which was validated by MALDI time-of-flight tandem mass spectrometry and high-resolution mass spectrometry analysis of lipid extracts. Based on the isotopic ion distribution profile, both esters and glycerophospholipids were predicted compounds and may be playing an important role in gall development. Our results indicate that the MALDI-MSI technology is a promising tool to identify secondary metabolites as well as peptides and proteins in complex plant tissues like galls to decipher molecular processes responsible for infection and maintenance of these feeding sites during nematode parasitism.

Sulfonated Phenylene/Quinquephenylene/Perfluoroalkylene Terpolymers as Proton Exchange Membranes for Fuel Cells

A novel series of terpolymers (SQF) containing sulfophenylene, quinquephenylene, and perfluoroalkylene groups in the polymer main chain were designed and synthesized as proton exchange membranes for fuel cells. The terpolymers with high molecular weight (Mw = 179–207 kDa, Mn = 41–50 kDa) and different ion exchange capacity (IEC) values (1.70, 2.56, and 3.34 mequiv g–1) gave flexible self-standing membranes by solution casting. Compared to the two-component (sulfophenylene and quinquephenylene segments) copolymer membranes, the incorporation of the third component, perfluoroalkylene groups, resulted in better water utilization for the proton conduction, while it did not alter the other properties such as gas permeability and mechanical strength. The selected membrane (SQF-3 with IEC = 2.56 mequiv g–1) exhibited high fuel cell performance under high- and low-humidity conditions with maximum power density reaching 0.97 W cm–2 at 100% RH (relative humidity) and 0.82 W cm–2 at 30% RH, respectively, at a curren...

Potential of capillary electrophoresis mass spectrometry for the characterization and monitoring of amine-derivatized naphthenic acids from oil sands process-affected water

Capillary electrophoresis coupled to mass spectrometry (CE–MS) was used for the analysis of naphthenic acid fraction compounds (NAFCs) of oil sands process-affected water (OSPW). A standard mixture of amine-derivatized naphthenic acids is injected directly onto the CE column and analyzed by CE–MS in less than 15min. Time of flight MS analysis (TOFMS), optimized for high molecular weight ions, showed NAFCs between 250 and 800m/z. With a quadrupole mass analyzer, only low-molecular weight NAFCs (between 100 and 450m/z) are visible under our experimental conditions. Derivatization of NAFCs consisted of two-step amidation reactions mediated by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), or mediated by a mixture of EDC and N-hydroxysuccinimide, in dimethyl sulfoxide, dichloromethane or ethyl acetate. The optimum background electrolyte composition was determined to be 30% (V/V) methanol in water and 2% (V/V) formic acid. NAFCs extracted from OSPW in the Athabasca oil sands region were used to demonstrate the feasibility of CE–MS for the analysis of NAFCs in environmental samples, showing that the labeled naphthenic acids are in the mass range of 350 to 1500m/z.

Ladder-type aromatic block copolymers containing sulfonated triphenylphosphine oxide moieties as proton conductive membranes

The synthesis and characterization of ladder-type aromatic block copolymers containing sulfonated triphenylphosphine oxide moieties (LadP-SPE) are reported. Through aromatic nucleophilic substitution polycondensation and Pd-catalyzed intrapolymer Heck reaction, the target copolymers LadP-SPE with high molecular weight (Mn = 47–50 kDa, Mw = 289–579 kDa) and different ion exchange capacity (IEC) values (1.04, 1.84 and 2.22 meq g−1, by titration) were prepared. By solution casting method, all the copolymers gave transparent and bendable membranes. The membrane with IEC = 2.22 meq g−1 exhibited high proton conductivity in wide range of relative humidity (RH) at 80 °C (ca. 1.6 mS cm−1 at 20% RH and 351.2 mS cm−1 at 95% RH). Moreover, the stiff ladder structure strengthened the molecular chain which contributed to the membrane with high IEC value and water uptake to have desirable mechanical stability up to 90% RH at 80 °C.

The Use of Shift Reagents in Ion Mobility-Mass Spectrometry: Studies on the Complexation of an Active Pharmaceutical Ingredient with Polyethylene Glycol Excipients

Gas-phase ion mobility studies of mixtures containing polyethylene glycols (PEG) and an active pharmaceutical ingredient (API), lamivudine, have been carried out using electrospray ionization-ion mobility spectrometry-quadrupole-time-of-flight mass spectrometry (ESI-IMS-Q-TOF). In addition to protonated and cationized PEG oligomers, a series of high molecular weight ions were observed and identified as noncovalent complexes formed between lamivudine and PEG oligomers. The noncovalent complex ions were dissociated using collision induced dissociation (CID) after separation in the ion mobility drift tube to recover the protonated lamivudine free from interfering matrix ions and with a drift time associated with the precursor complex. The potential of PEG excipients to act as "shift reagents," which enhance selectivity by moving the mass/mobility locus to an area of the spectrum away from interferences, is demonstrated for the analysis of lamivudine in a Combivir formulation containing PEG and lamivudine.

Selective Ion Filtering by Digital Thresholding: A Method To Unwind Complex ESI-Mass Spectra and Eliminate Signals from Low Molecular Weight Chemical Noise

In this work, we present a simple method by which to preferentially detect either high molecular weight or low molecular weight ions generated by electrospray ionization. This approach, termed selective ion filtering by digital thresholding (SIFdT) is demonstrated on a commercial ESI-TOF instrument that employs a fast digitizer coupled to a microchannel plate detector. The digital representation of each individual scan is digitally filtered prior to spectral coaddition. As larger, more highly charged ions induce a more intense response than low molecular weight singly charged species, a digital threshold can be set that precludes the detection of singly charged species yet permits the efficient detection of larger, more highly charged species. In this work, we demonstrate the applicability of this approach to eliminate low molecular weight chemical noise in ESI-TOF spectra of oligonucleotide and protein ions, demonstrate improved dynamic range for analyte solutions containing high levels of low MW constituents, and show that spectra acquired at different digital thresholds can be subtracted to yield spectra of low molecular weight constituents with improved mass measurement accuracies. A notional scheme is presented in which an alternative digitization approach is employed using multiple differentially thresholded data streams to allow improved internal mass calibration and higher resolution ion partitioning.

Analysis of Megadalton Ions Using Cryodetection MALDI Time-of-Flight Mass Spectrometry

Presented are initial results from the first commercially available matrix-assisted laser desorption/ionization time-of-flight mass spectrometer specifically designed for the sensitive detection of very high mass ions (macromizer, Comet AG). This new instrument utilizes a 16-element superconducting tunnel junction detector coupled with a fully adjustable gimbal-mounted ion source/focusing region that allows unparalleled sensitivity for detection of singly charged high molecular weight ions. Using this new technology, the singly charged ions in the megadalton region are detected from immunoglobulin M and von Willebrand factor proteins. This detector technology also measures the kinetic energy of the particles impacting the detector, which can be correlated to the charge of the particles. Immunoglobulin G and streptavidin were used to demonstrate the ability of the macromizer instrument to detect high-mass ions and to discern the charge state of the ions.

Methods for Generating Protein Molecular Ions in ToF-SIMS

One of the greatest challenges in mass spectrometry lies in the generation and detection of molecular ions that can be used to directly identify the protein from the molecular weight of the molecular ion. Typically, proteins are large (MW > 1000), nonvolatile, and/or thermally labile, but the vaporization process produced by many mass spectrometry techniques including time-of-flight secondary ion mass spectrometry (ToF-SIMS) is inherently limited to generating ions from smaller compounds or fragments of the parent molecule, making the identification of proteins complex. The application of specific molecules to aid in the generation of high molecular weight ions in ToF-SIMS has been recognized for some time. In this study we have developed a matrix-SAM substrate preparation technique based on the self-assembly of a matrix-like molecule, mercaptonicotinic acid (MNA), on gold. We then compare this substrate with two existing ToF-SIMS sample preparation techniques, cationized alkane thiol and matrix-enhanced SIMS (MESIMS). The results of this study illustrate that while there is a range of methods that can be used to improve the molecular ion yield of proteins in ToF-SIMS, their efficacy and reproducibility vary considerably and crucially are linked to the sample preparation and/or protein application methods used. Critically, the MNA modified substrate was able to simultaneously induce molecular ions for each protein present in a multicomponent solution, suggesting that this sample preparation technique may have future application in proteomics and DNA analysis.

On-line photo-derivatization with flow injection and liquid chromatography–atmospheric pressure electrospray mass spectrometry for the identification of indoles

The application of on-line photochemistry with flow injection (FI) and liquid chromatography (LC) in conjunction with atmospheric pressure electrospray mass spectrometry (LC–APESI–MS) for the identification of similar indole derivatives is reported here. The photo-transformation of the indole compounds is strongly affected by the substituent groups on the aromatic and heterocyclic rings. Upon photolysis for 2.5 min, the mass spectrum of tryptamine (Try) which has no OH substituent on the aromatic ring does not differ greatly from that obtained without photolysis. However, after photolysis of serotonin (Ser) which has one OH group on C5 of the aromatic ring, the mass spectrum indicates the formation of dimers and higher molecular weight ions. The fragmentation pattern of 5-hydroxytryptophol (Phol) without photolysis resembles that of Ser with a base peak of m/ z 160. Upon photolysis using MeOH–H 2O (10/90), Phol is found to form a base peak at m/ z 375 (100%) and a major peak at m/ z 214 (66%) in addition to other ions with lower abundance. Melatonin (Mel) and tryptophan (Phan) upon photolysis are found to form high molecular weight ions with a relative low abundance. The mass spectrum of indole-3-acetic acid (Inaa) with on-line photolysis also shows different ions that are not formed without photolysis.

Electrospray Mass Spectrometry of Borane Salts: Observation of High Molecular Weight Ion Clusters

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectrospray Mass Spectrometry of Borane Salts: Observation of High Molecular Weight Ion ClustersCornelis E. C. A. Hop, Dovas A. Saulys, and Donald F. GainesCite this: Inorg. Chem. 1995, 34, 8, 1977–1978Publication Date (Print):April 1, 1995Publication History Published online1 May 2002Published inissue 1 April 1995https://doi.org/10.1021/ic00112a003RIGHTS & PERMISSIONSArticle Views136Altmetric-Citations16LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (288 KB) Get e-AlertsSupporting Info (2)»Supporting Information Supporting Information Get e-Alerts

A novel GC/MS derivatization method for amphetamines.

Many widely used methods for derivatizing drugs of the amphetamine group for GC/MS are problematic. The difficulties with these methods include incompatibility with other derivatizing agents, short column life, lack of abundant high molecular weight ions, and the potential for interference from other drugs. The present procedure is an effort to reduce some of these problems by the use of a novel derivatizing agent, N-methyl-N-t-butyldimethylsilyl trifluoroacetamide (MTBSTFA). We describe here an MTBSTFA derivatization method for amphetamine (AMP) and methamphetamine (MAMP) that leads to stable derivatives that are well-separated from potential interferences and features high molecular weight fragments suitable for selected ion monitoring. The procedure is linear to approximately 3000 ng/mL for both AMP and MAMP and appears to be both precise and sensitive. Furthermore, it seems to have no adverse effect on column life.

Identification of methamphetamines and over-the-counter sympathometic amines by full-scan GC-ion trap MS with electron impact and chemical ionization.

An underivatized methane chemical ionization (CI) assay for measuring amphetamines in urine was evaluated against derivatized electron impact (EI) assays using a gas chromatograph-ion trap mass spectrometer. The full-scan CI mass spectra of methamphetamine, ephedrine/pseudoephedrine, and phentermine were compared with the full scan and three-ion EI mass spectra of heptafluorobutyric anhydride (HFBA) and 4-carbethoxyhexafluorobutyryl chloride (CB) derivatives. The fragmentation patterns for these compounds were nearly identical for the three major high molecular weight ions (m/z 254, 210, and 169 for EI-HFBA derivatives, and m/z 308, 262, and 280 for EI-CB derivatives). The CI mass spectra of the underivatized drugs contained more discernible differences at the higher molecular weights, including m/z 119, 148, and 150 for methamphetamine, 148, 166, and 176 for ephedrine/pseudoephedrine, and 91, 133, and 150 for phentermine. The within-run precision ranged from 7-9% for CI versus 5-6% for EI with HFBA derivatization (mean 500 ng/mL, n = 5). The limits of detection (LOD) for amphetamine and methamphetamine were 2.4 and 8.6 ng/mL, respectively, for CI versus 0.7 and 1.4 ng/mL for EI. The limits of quantitation (LOQ) were 4.5 and 19.1 ng/mL for CI versus 1.4 and 5.7 ng/mL for EI. The use of full-scan mass spectral analysis with either electron impact or chemical ionization provides additional qualitative data that may be helpful for measuring methamphetamine in the presence of other sympathomimetic amines.

α- D-Glucopyranosyl flouride as a D-glucopyranosyl donor for a glycosyltransferase complex from streptococcus mutans FA1

α- D-Glucopyranosyl fluoride can serve as the D-glucopyranosyl donor for the glycosyltransferase from Streptococcus mutans. The products of the reaction are a D-glucan of high molecular weight and fluoride ion. The rate of reaction was measured by an electrode specific for the fluoride ion. The reaction was inhibited by the substrate at concentrations >30m M, but was not affected by fluoride ion. There was little inhibition of the reaction by a series of monosaccharides, except for 2-amino-2-deoxy D-glucose, D-mannitol, and 3-deoxy- D- ribo-hexose. Maltose, isomaltose, isomaltotriose, and D-fructose all stimulated the release of fluoride from α- D-glucopyranosyl fluoride.