The influence of structural features on facile McLafferty‐type, even‐electron rearrangements in tandem mass spectra of carboxylate anions

Grossert, J. Stuart; Cook, Matthew; White, Robert L.

doi:10.1002/rcm.2506

Cited by 38 publications

(43 citation statements)

References 35 publications

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“…A cleavage could then occur with the aid of the side chain, leading to a double bond end group and a propionic acid amide end group. This kind of rearrangement has already been described in the ESI-MS/MS of carboxylate anions 29 and the esters of N- acetylated peptides. 30 In a complementary fashion, the double series C and C 0 could be explained by an a-cleavage of the backbone between the CH 2 groups followed by a cleavage of the side group resulting in the formation of a methylene imine end group (Scheme 2(e)).…”

Section: Resultsmentioning

confidence: 61%

Characterization of different poly(2‐ethyl‐2‐oxazoline)s via matrix‐assisted laser desorption/ionization time‐of‐flight tandem mass spectrometry

Baumgaertel

Weber

Knop

et al. 2009

Rapid Comm Mass Spectrometry

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Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) coupled with CID (collision-induced dissociation) has been used for the detailed characterization of two poly(2-ethyl-2-oxazoline)s as part of a continuing study of synthetic polymers by MALDI-TOF MS/MS. These experiments provided information about the variety of fragmentation pathways for poly(oxazoline)s. It was possible to show that, in addition to the eliminations of small molecules, like ethene and hydrogen, the McLafferty rearrangement is also a possible fragmentation route. A library of fragmentation pathways for synthetic polymers was also constructed and such a library should enable the fast and automated data analysis of polymers in the future.

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Section: Resultsmentioning

confidence: 61%

Characterization of different poly(2‐ethyl‐2‐oxazoline)s via matrix‐assisted laser desorption/ionization time‐of‐flight tandem mass spectrometry

Baumgaertel

Weber

Knop

et al. 2009

Rapid Comm Mass Spectrometry

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“…4B). During the fragmentation, one fragment may exchange one AMU with the other fragment (7,15). Also, molecular ions become variably hydrated within argon collision cells (25).…”

Section: Fig 2 Carbohydrate Composition (A) Of Capsular Ps From 6a␣mentioning

confidence: 99%

Discovery of a New Capsular Serotype (6C) within Serogroup 6 ofStreptococcus pneumoniae

et al. 2007

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Using two monoclonal antibodies, we found subtypes among pneumococcal isolates that are typed as serotype 6A by the quellung reaction. The prevalent subtype bound to both monoclonal antibodies and was labeled here 6A␣, whereas the minor subtype bound to only one monoclonal antibody and was labeled 6A␤. To determine the biochemical nature of the two serologically defined subtypes, we purified capsular polysaccharides (PSs) from the two subtypes and examined their chemical structures with gas-liquid chromatography and mass spectrometry. The study results for 6A␣ PS are consistent with the previously published structure of 6A PS, which is 32) galactose (133) glucose (133) rhamnose (133) Streptococcus pneumoniae is a major human pathogen that is responsible for a large percentage of cases of pneumonia, meningitis, otitis media, and sepsis (6). All pathogenic pneumococci are known to display one of many structurally diverse carbohydrate capsules, which shield pneumococci from host phagocytes and increase their pathogenicity (2). Antisera to a capsule type can be used to treat patients infected with the pneumococci expressing that capsule type (4). Consequently, for the past century, the serological types of pneumococcal capsules have been extensively investigated with quellung reactions. These studies have culminated in identifying 90 different pneumococcal capsules with distinct serological patterns (9) and chemical structures (10).Not all 90 serotypes are equally pathogenic. For instance, serotypes 6A and 6B account for 4.7% and 7%, respectively, of cases of invasive pneumococcal disease in the U.S. population (19,20). Because of their medical importance, the molecular natures of serotype 6A and its related serotype, serotype 6B, have been studied extensively. Biochemical studies found that the capsular polysaccharides (PSs) of serotypes 6A and 6B are linear polymers with a repeating unit containing four monosaccharides/alditols: rhamnose, ribitol-phosphate (P), galactose, and glucose (10). The two PSs are identical except for a difference in the linkage between rhamnose and ribitol (see Fig. 6).Currently available pneumococcal vaccines are designed to elicit antibodies to the capsular PSs of the most common pneumococcal serotypes. Since vaccine-induced immunoprotection is serotype specific, serotyping pneumococcal isolates from patients is an important tool for monitoring the effectiveness of pneumococcal vaccines (3). Because the classical quellung reaction with rabbit antisera is tedious to perform (13), we have developed a new serotyping system based on mouse monoclonal antibodies (mAbs) and a multiplexed immunoassay (27). While validating the new system, we found that a minor fraction of the isolates determined to be serotype 6A by quellung reaction bound to one 6A-specific mAb (Hyp6AG1) but not to the other (Hyp6AM3), whereas the majority of the serotype 6A isolates bound to both mAbs (12). To distinguish between the isolates, we have labeled the isolates reacting with both mAbs as 6A␣ and those reacting wit...

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“…This report assumes significance in view of the fact that there exist very few reports in the literature on McLafferty-type rearrangement in even electron ions formed in ESI conditions. [13,14] For example, Anbalagan et al, observed McLafferty-type rearrangement in the CID of cationized esters of N-acetylated peptides, [13] and Grossert and coworkers in the CID of carboxylate anions. [14] Another fragment ion that is absent for isomer 1, but present in the MS/MS of protonated 2 is m/z 97.…”

Section: Jms Lettermentioning

confidence: 99%

“…As there exist no reports in the literature on mass spectrometric studies on belactosin precursors and because of few reports on McLafferty rearrangement [5 -11] in even electron ions [12] under atmospheric pressure ionization (API) conditions, [13,14] we have undertaken a detailed study of the isomeric precursors in the present work (Scheme 1).…”

mentioning

confidence: 99%

Diastereoselectivity in the McLafferty‐type rearrangement of protonated precursors of belactosin derivatives using electrospray ionization (ESI) and atmospheric pressure photo ionization (APPI) tandem mass spectrometry

et al. 2008

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Diastereoselectivity in the McLafferty-type rearrangement of protonated precursors of belactosin derivatives using electrospray ionization (ESI) and atmospheric pressure photo ionization (APPI) tandem mass spectrometry Small molecules that target the 20S proteosome inhibition appear to be an apt choice for cancer chemotherapy. [1] Many natural products possessing the 2-oxetanone (β-lactone) moiety exhibit biological activity such as antibiotic, antitumor and antiobesity. [2] Belactosins, belonging to the class of 2-oxetanones, have recently been reported to inhibit the 20S proteasome in vitro (IC 50 = 0.4 µM, chymotrypsin-like activity) [3] in a yeastbased assay of Streptomycin metabolites. As a part of an ongoing synthetic research program at our institute, a pair of diastereomeric precursors of belactosin derivatives were synthesized.[4] An initial examination of the electrospray ionization (ESI) mass spectra of the two isomers revealed a diastereoselectivity of the McLafferty fragmentation in the protonated isomers. As there exist no reports in the literature on mass spectrometric studies on belactosin precursors and because of few reports on McLafferty rearrangement [5 -11] in even electron ions [12] under atmospheric pressure ionization (API) conditions, [13,14] we have undertaken a detailed study of the isomeric precursors in the present work (Scheme 1).ESI mass spectra of 1 and 2 (Scheme 1) were recorded using a quadrupole time-of-flight (Q-TOF) mass spectrometer (QSTAR XL; Applied Biosystems/MDS Sciex, Foster City, CA, USA), equipped with an ESI source. The data acquisition was under the control of Analyst QS software (Foster City, CA). The typical source conditions were: capillary voltage, 5.00 kV; declustering potential, 60 V; focusing potential, 280 V; declustering potential 2, 10 V; resolution 8000 (full-width half-maximum). Ultra high pure nitrogen was used as the curtain gas and collision gas, whereas zero air was used as the nebulizer. The [M + H] + ions were selected as precursors by the quadrupole and allowed to collide with nitrogen gas in the collision cell. The product ions were then detected by a time-of-flight (TOF) analyzer. The samples were infused into the ESI source at a flow rate of 15-20 µl/min by using an in-built syringe pump.Atmospheric pressure photo ionization (APPI) mass spectra were recorded on a bench top triple quadrupole mass spectrometer, Quattro micro (Waters, Manchester, UK) equipped with an APPI interface, and a Masslynx v.4.1 software was used for data acquisition and processing. The APPI system is composed of a heated nebulizer to vaporize the sample prior to inducing ionization, and a power supply for krypton lamp to continuously generate 10 eV photons for photoionization. The nebulizing gas (nitrogen) and desolving gas (nitrogen) were delivered at a flow rate of 50 and 400 l/h, respectively. The optimum source conditions were: repeller voltage 0.92 V, cone voltage 25 V, extractor 3 V, rf lens 0.2 V, source temperature 100• C, APPI probe temperature 300• C. The mass s...

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The influence of structural features on facile McLafferty‐type, even‐electron rearrangements in tandem mass spectra of carboxylate anions

Cited by 38 publications

References 35 publications

Characterization of different poly(2‐ethyl‐2‐oxazoline)s via matrix‐assisted laser desorption/ionization time‐of‐flight tandem mass spectrometry

Characterization of different poly(2‐ethyl‐2‐oxazoline)s via matrix‐assisted laser desorption/ionization time‐of‐flight tandem mass spectrometry

Discovery of a New Capsular Serotype (6C) within Serogroup 6 ofStreptococcus pneumoniae

Diastereoselectivity in the McLafferty‐type rearrangement of protonated precursors of belactosin derivatives using electrospray ionization (ESI) and atmospheric pressure photo ionization (APPI) tandem mass spectrometry

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