Methods of ionization

Polymers have a wide range of applications depending on their composition, size, and architecture. Varying any of these three characteristics can greatly impact the resulting chemical, physical, and mechanical properties. While many techniques are available to determine polymer composition and size, determining the exact polymer architecture is more challenging. Herein, tandem mass spectrometry (MS/MS) and ion mobility mass spectrometry (IM-MS) methods are utilized to derive crucial architectural information about dithiol-yne comb polymers. Based on their unique fragmentation products and IM drift times, dithiol-yne oligomers with distinct architectures were successfully differentiated and characterized. Additionally, experimental collision cross-sections (Ω) derived via IM-MS were compared to theoretically extracted Ω values from molecular dynamics simulated structures to deduce the architectural motif of these comb oligomers. Overall, this work demonstrates the benefits of combining various mass spectrometry techniques in order to gain a complete understanding of a complex polymer mixture.

With the dramatic increase in the number of new chemical entities (NCEs) arising from combinatorial chemistry and modern high-throughput bioassays, novel bioanalytical techniques are required for the rapid determination of the metabolic stability and metabolites of these NCEs. Knowledge of the metabolic site(s) of the NCEs in early drug discovery is essential for selecting compounds with favorable pharmacokinetic credentials and aiding medicinal chemists in modifying metabolic "soft spots". In development, elucidation of biotransformation pathways of a drug candidate by identifying its circulatory and excretory metabolites is vitally important to understand its physiological effects. Mass spectrometry (MS) and nuclear magnetic resonance (NMR) have played an invaluable role in the structural characterization and quantification of drug metabolites. Indeed, liquid chromatography (LC) coupled with atmospheric pressure ionization (API) MS has now become the most powerful tool for the rapid detection, structure elucidation, and quantification of drug-derived material within various biological fluids. Often, however, MS alone is insufficient to identify the exact position of oxidation, to differentiate isomers, or to provide the precise structure of unusual and/or unstable metabolites. In addition, an excess of endogenous material in biological samples often suppress the ionization of drug-related material complicating metabolite identification by MS. In these cases, multiple analytical and wet chemistry techniques, such as LC-NMR, enzymatic hydrolysis, chemical derivatization, and hydrogen/deuterium-exchange (H/D-exchange) combined with MS are used to characterize the novel and isomeric metabolites of drug candidates. This review describes sample preparation and introduction strategies to minimize ion suppression by biological matrices for metabolite identification studies, the application of various LC-tandem MS (LC-MS/MS) techniques for the rapid quantification and identification of drug metabolites, and future trends in this field.

ADVERTISEMENT RETURN TO ISSUEPREVReviewNEXTHigh-sensitivity Analytical Approaches for the Structural Characterization of GlycoproteinsWilliam R. Alley, Jr.†‡, Benjamin F. Mann†‡, and Milos V. Novotny*†‡§View Author Information† Department of Chemistry, Indiana University, Bloomington, Indiana, United States‡ National Center for Glycomics and Glycoproteomics, Indiana University, Bloomington, Indiana, United States§ Indiana University School of Medicine, Indiana University, Indianapolis, Indiana, United States*E-mail: [email protected]. Phone: (812) 855-4532. Fax: (812) 855-8300.Cite this: Chem. Rev. 2013, 113, 4, 2668–2732Publication Date (Web):March 27, 2013Publication History Received4 September 2012Published online27 March 2013Published inissue 10 April 2013https://pubs.acs.org/doi/10.1021/cr3003714https://doi.org/10.1021/cr3003714review-articleACS PublicationsCopyright © 2013 American Chemical SocietyRequest reuse permissionsArticle Views6426Altmetric-Citations263LEARN 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 InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Carbohydrates,Chemical biology,Chemical structure,Monomers,Peptides and proteins Get e-Alerts

Objective To find differential expression proteins in patients with T cell non-Hodgkin’ s lymphoma (T-NHL) by using surface-enhanced laser desorption and ionization time-of-flight mass spectrometry (SELDI-TOF-MS) technique and study their related clinical application value and prospect.Methods Serum protein of 36 T-NHL patients and 30 DLBCL patients were detected by the SELD1-TOF-MS technique and weak cation exchange (wcx-2) chip.Lactate dehydrogenase (LDH) was detected by biochemistry method.Beta2-microglobulin (β2-MG) was detected by enzyme-linked immunesorbent assay (ELISA).The significant different protein spectrometry were analyzed between DLBCL patients and T-NHL patients.The correlation analysis with protein spectrometry,disease staging,LDH and β2-MG were analyzed with Spearman.Results Nine potential candidate proteins,including the peak intensity of M/Z 1142.67,1451.43,1472.49,1512.03,3194.22,3267.41,3933.86,4593.12 and 9182.24,were identified in T-NHL patients.The 9 protein markers had no contact with disease staging of T-NHL (P ＞ 0.05).The protein markers of 4593.12 and 9182.24 were high level in T-NHL patients.LDH in these two protein markers’ positive group [(290.82±29.95) U/L,(283.94±100.94) U/L] was higher than that in negative group [(169.22±55.42) U/L,(169.50±59.25) U/L](t =-3.199,P =0.004; t =-2.378,P =0.026),and LDH was positive correlation with these two protein spectrometry (r =0.265,r =0.178,P ＜ 0.01).There was no statistically significant difference ofβ2-MG between these two protein markers’ positive group and negative group (P ＞ 0.05).The other 7 protein markers were low level in T-NHL patients,and there was no statistically significant difference of LDH and β2-MG in these 7 protein markers (P ＞ 0.05).Conclusion The protein marker of 4593.12 and 9182.24 may be the specific serological markers to identify T-NHL.The combination of these two protein markers and LDH may assess the tumor load,and provide guiding value for clinical treatment. Key words: Spectrometry, mass, matrix-assisted laser desorption-ionization; T-lymphocytes; Lymphoma, non-Hodgkin's

APPLICATION OF PAPER SPRAY IONIZATION MASS SPECTROMETRY AND RELATED TECHNIQUES IN THE DIRECT ANALYSIS OF BIOLOGICAL MATRICES FOR DETECTION OF DRUGS - A REVIEW. In recent years, technological development in analytical instrumentation has progressed vigorously, which has allowed the evolution of analytical techniques that play an indispensable role within society, highlighting mass spectrometry. Parallel to the technological advance of this technique, the development of new ionization methods that are simpler, faster, and allow direct analysis without the need for prior treatment or sample processing is underway. The methods of ambient ionization derived from paper spray have been developing rapidly in current days, mainly in the forensic field, due to the chemical modifications made in the paper substrate and the introduction of new types of organic materials that function as a probe/substrate to collect, store, and ionize the sample, then enabling more efficient and selective analyzes. This review highlights direct analyzes by applying paper spray ionization in the forensic field and some variations of this technique, including Thread Spray Ionization (TSI) when a fabric thread is used; Touch Spray Ionization (TSI), which uses materials such as metallic needles, medical swabs, and wooden sticks; Fiber Spray Ionization (FSI), which applies polymeric fibers as substrates.

Qualitative and Quantitative Analysis of Triacylglycerols by Atmospheric Pressure Ionization (APCI and ESI) Mass Spectrometry Techniques

Accurate identification of fossil pigments is essential if they are to be used as biomarker compounds in palaeolimnological studies. In recent years High Performance Liquid Chromatography (HPLC) has greatly enhanced the efficiency with which fossil pigments can be characterised and quantified. Using HPLC, undegraded pigments are typically identified through retention times, absorbance spectra and co-chromatography with authentic reference standards. However, lake sediments may also contain degraded pigments for which there are often no standards, and which may be difficult to identify using HPLC alone. In this study, we submitted HPLC fractions of fossil pigments and pigment derivatives collected from a meromictic lake in south west Tasmania, to a combination of Mass Spectrometry (MS) techniques including Electron Impact (EI) and static Liquid Secondary Ion MS (LSIMS) to identify their molecular ion characteristics and organic chemical composition. Mass Spectrometry permitted the detection of specific mass ions which were used to verify the identity of pigments and their derivatives. These included five carotenoids, chlorophyll a and derivatives, three previously described bacteriochlorophyll c derivatives with molecular weights of 770, 784, and 802, and two undescribed derivatives of bacteriochlorophyll c with molecular weights of 766 and 788. With these improved identifications we speculate on the pathways and modes of pigment degradation in the lake and asses the value of the degraded pigments as biomarkers. The use of MS permitted the identification of a greater number of signature pigments of algal and bacterial communities thus increasing the palaeolimnological value of the sediments. These methods are best applied in fossil pigment studies where there are a large number of unknown pigments and pigment degradation products, and where there are no authentic standards for co-chromatography. Practical suggestions for pigment MS are included in the discussion.

Modern Atmospheric Pressure Surface Sampling/Ionization Techniques in Mass Spectrometry

Modern Atmospheric Pressure Surface Sampling/Ionization Techniques in Mass Spectrometry

Gaur egun, nahiko informazio ageria ematen dute biomolekulak eta materialak karakterizatzeko erabiltzen diren laborategi-teknika analitikoek, baina azaldu ezin diren efektuak edo emaitzak lortzen dira askotan. Horregatik, informazio hau lortzeko, hau da, molekulen mikroegiturak karakterizatzeko edota gertatu diren kutsadurak ezagutzeko ere, gero eta gehiago hedatzen ari da teknika bat, Matrix Assisted Laser Desorption-Ionization/Time of Flight Mass Spectrometry (MALDI/TOF-MS) izenekoa, edo laserraren bidezko desortzio-ionizazio matrizez lagundua/hegaldi-denbora masa-espektrometria teknika. Masa-espektrometria delako karakterizazio teknika hau hainbat alorretara hedatu da, masa molarra jakitea ahalbidetzen duelako inolako zatiketarik gabe eta, aldi berean, ehun edo material baten banaketaren berri ematen duelako Imaging Mass Spectrometry (IMS) edo masa-espektrometriaren bidezko irudia deritzon teknikari esker. Lan honek helburu hartuko du teknika berri honen oinarriak eta aplikazioak azaltzea eta aztertzea.

Secondary ion production by electron and ion bombardment of alkali halides

GLYCOFORM, GLYCOTYPE LINKAGE AND BRANCHING DETAIL OF THE CD2 ADHESION DOMAIN BY DESOLVATION MASS SPECTROMETRY: SFCI-MS AND ESI-MS

Massenspektrometrie organischer Verbindungen : von Wolfgang Benz, Akademische Verlagsgesellschaft, Frankfurt am Main, 1969, 419 Seiten, Preis DM 75.—.

Purines and pyrimidines are of interest owing to their significance in processes in living organisms. Mass spectrometry is a promising analytical tool utilized in their analysis. Two atmospheric pressure ionization (API) methods (electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI)) in both negative and positive modes applied to selected purine and pyrimidine metabolites (markers of inherited metabolic disorders) were studied. APCI is less sensitive to alkali metal cations present in a sample and offers higher response than ESI for studied compounds. Both of the techniques afford quasi-molecular ions, but fragmentation also occurs to a certain extent. However, the application of collision-induced dissociation of quasi-molecular ions is essential to confirm a certain metabolite in a sample. Fragmentation of both positive and negative ions was evaluated using multi-stage mass spectrometric experiments. Typical neutral losses correspond to molecules NH(3), H(2)O, HCN, CO, H(2)NCN, HNCO and CO(2). The ion [NCO](-) arises in the negative mode. The cleavage of the glycosidic C-N bond is characteristic for relevant metabolites. Other neutral losses (CH(2)O, C(2)H(4)O(2) and C(3)H(6)O(3)) originate from fragmentation of the glycosidic part of the molecules. In addition to fragmentation, the formation of adducts of some ions with applied solvents (H(2)O, CH(3)OH) was observed. The composition of the solution infused into the ion source affects the appearance of the mass spectra. Tandem mass spectra allow one to distinguish compounds with the same molecular mass (uridine-pseudouridine and adenosine-2'-deoxyguanosine). Flow injection analysis APCI-MS/MS was tested on model samples of human urines corresponding to adenosine deaminase deficiency and xanthine oxidase deficiency. In both cases, the results showed potential diagnostic usefulness.

The mechanism of atmospheric pressure (AP) laser ionization of water and water/glycerol liquid samples at a 3-microm wavelength is studied experimentally. For the ion desorption, an in-house built Yb : YAG-pumped optical parametric oscillator (OPO) infrared (IR) laser has been coupled with AP MALDI ion source interfaced to an ion trap mass spectrometer (MS). It has been shown that water is primarily responsible for ion generation in water/glycerol samples, while glycerol increases the solution viscosity and decreases the water evaporation rate and sample losses. In contrast to AP UV-MALDI, the electric field in the case of AP IR-MALDI does not assist in ion production. It was found that the absence of the electrical field provides the optimum ionization condition both for water and water/glycerol liquid samples at the 3-microm laser irradiation. A two-stage ion formation mechanism, which includes the initial emission of microdroplets and release of molecular ions at the second stage, can explain the experimentally observed ion signal dependencies upon the voltage applied between MS inlet and the MALDI sample plate. Postionization using additional corona discharge APCI increases the observed signal by approximately 50%, which indicates that some portion of the analyte is desorbed in the form of neutral molecules.