Recently, we demonstrated that a radio-frequency-free electromagnetostatic (rf-free EMS) cell could be retrofitted into a triple quad mass spectrometer to allow electron-capture dissociation (ECD) without the aid of cooling gas or phase-specific electron injection into the cell (Voinov et al., Rapid Commun Mass Spectrom 22, 3087–3088, 2008; Voinov et al., Anal Chem 81, 1238–1243, 2009). Subsequently, we used our rf-free EMS cell in the same instrument platform to demonstrate ECD occurring in the same space and at the same time with collision-induced dissociation (CID) to produce golden pairs and even triplets from peptides (Voinov et al., Rapid Commun Mass Spectrom 23, 3028–3030, 2009). In this report, we demonstrate that ECD and CID product-ion mass spectra can be recorded at high resolution with flexible control of fragmentation processes using a newly designed cell installed in a hybrid Q-TOF tandem mass spectrometer.

Formation of negative ions via dissociative electron attachment (DEA) to the amino acid serine in the gas phase was studied using two different crossed electron/molecular beam techniques and quantum chemical calculations. Resonance electron capture mass spectrum and effective ion yield curves of 16 negative ions were measured over the electron energy range from close to 0 to 11 eV. The negative ions from serine were detected from resonance states in the vicinity of 0, 1.3, 5, and 8 eV. The dominant reaction channel at low electron energies was (M-H)(-). The relative cross section for this ion exceeds more than 20 times that of any other fragment negative ions. A high-resolution experiment was applied to study fine structures in (M-H)(-) cross section. We have found that the second OH group influences some dissociative channels. Quantum chemical calculations were applied to interpret products of the DEA reaction channels.

Summary Tansy ragwort (Senecio jacobaea) was evaluated for animal and human health hazard using the Salmonella/mammalian-microsome mutagenicity test. An acetone extract of tansy ragwort (TR) produced a negative mutagenic response for bacterial tester strains TA1535 and TA100 and a toxic response in tester strains TA1537 and TA98. Assay of this extract in the presence of mammalian liver microsomes (S-9) resulted in positive mutagenic responses in tester strains TA1535, TA1537, TA98 and TA100. Species differences were evaluated by use of liver microsome preparations from induced rat and uninduced sheep, beef, hamster, trout and rat. Only a slight species difference was demonstrated. A mixture of pyrrolizidine alkaloids (PA), extracted from TR flowers, produced a negative response in tester strains TA1535, TA1537, TA98 and TA100. A negative response was also demonstrated when the TR flower PA mixture was assayed with the Sal- monella tester strains and induced rat liver microsomes (IRLM). A mixture of PA extracted from Senecio longilobus also produced a negative response. The major PA present in TR, jacobine, produced a negative response without

High mass resolving power was applied to study resonance electron capture by glycine, alanine, and valine, and accurate mass measurements helped to distinguish between some negative ions having the same nominal masses. It was established that the C- and N-terminal negative ions of the same nominal masses were formed at different electron energies from different resonance states. The typical fragmentation pathways in deprotonated amino acids via loss of water initiated by collisional activation were not observed upon resonant electron capture by aliphatic amino acids. Instead, [M-18](-) negative ions in the vicinity of 5 eV were found to be associated with simultaneous loss of either ammonia and a hydrogen atom or an amino group and a hydrogen molecule.

Spleen is a prime organ in which immuno-stimulation takes place in mammalians. Proteome analysis was used to investigate the elicited effects on mouse splenocytes upon exposure to holothurian triterpene glycosides. Cucumarioside A2-2, and Frondoside A, respectively, have been used to in-vitro stimulate primary splenocyte cultures. Differential protein expression was monitored by 2D gel analysis and proteins in spots of interest were identified by MALDI ToF MS and nano LC-ESI Q-ToF MS/MS, respectively. Differential image analysis of gels from control vs. gels from stimulated primary splenocyte cultures showed that approximately thirty protein spots were differentially expressed. Prime examples of differentially expressed proteins are NSFL1 cofactor p47 and hnRNP K (down-regulated), as well as Septin-2, NADH dehydrogenase [ubiquinone] iron–sulfur protein 3, and GRB2-related adaptor protein 2 (up-regulated). Immuno-analytical assays confirmed differential protein expression. Together with results from proliferation and cell adhesion assays, our results show that cellular proliferation is stimulated by holothurian triterpene glycosides. In conclusion, holothurian triterpene glycosides are thought to express their immuno-stimulatory effects by enhancing the natural cellular defense barrier that is necessary to fight pathogens and for which lymphocytes and splenocytes have to be recruited constantly due to limited lifetimes of B-cells and T-cells in the body.

Liquid chromatography-tandem mass spectrometry (LC/MSn) coupled with various two-dimensional NMR methods are among the most practical approaches for analyzing proanthocyanidins from hops. Using these and other analytical approaches, it has been shown that hops contain a preponderance of polymeric material, including proanthocyanidins which are dominant, but small quantities of prodelphinidins and propelargonidins are also present. The flavanoids (+) catechin and proanthocyanidin B3 are the most representative followed by B1, B4 and C2. The relative proportions of the various proanthocyanidins vary greatly depending on the variety and climatic conditions as shown by differences in the proanthocyanidins in the same cultivar from different geographic regions. Proanthocyanidins have received a considerable amount of attention in the brewing industry because of their tendency to complex with proteins and contribute to non-biological haze formation, but they stabilize the organoleptic properties and color, and contribute to the astringency and bitterness, which are desirable attributes. Recent studies also show that these compounds, which are classic antioxidants, may also have significant beneficial health effects. Numerous proanthocyanidins including catechin, prodelphinidin B3, procyanidin B3 and epicatechin are present in beer.

A simple robust method to study resonance gas-phase reactions between neutral peptides of low volatility and free electrons has been designed and implemented. Resonance electron capture (REC) experiments were performed by several neutral model peptides and two naturally occurring peptides. The assignment of negative ions (NIs) formed in these gas-phase reactions was based on high mass-resolving power experiments. From these accurate mass measurements, it was concluded that fragment NIs formed by low (1-2 eV) energy REC are of the same types as those observed in electron capture/transfer dissociation, where the positive charge is a factor. The main feature resulting from these REC experiments by peptides is the occurrence of z(n)-1 ions, which are invariably of the highest abundances in the negative ion mass spectra of larger peptides. [M-H](-) NIs presumably the carboxylate anion structure dominate the REC spectra of smaller peptides. There was no evidence for the occurrence of the complementary reaction, i.e., the formations of c(n)+1 ions. Instead, c(n) ions arose without hydrogen/proton transfer albeit with lower abundances than that observed for z(n)-1 ions. Only the amide forms of small peptides showed more abundant ion peaks for the c(n) ions than for the z(n)-1 ions. The mechanisms for the N-C(alpha) bond cleavage are discussed.

A radio frequency-free (RFF), analyzer-independent cell has been devised for electron-capture dissociation (ECD) of ions. The device is based on interleaving a series of electrostatic lenses with the periodic structure of magnetostatic lenses commonly found in a traveling wave tube. The RFF electrostatic/magnetostatic ECD cell was installed in a Finnigan TSQ700 ESI triple quadrupole (QqQ) spectrometer, and its performance was evaluated by recording product-ion spectra of doubly protonated substance P, doubly protonated gramicidin S, doubly protonated neurotensin, and triply protonated neurotensin. These spectra were readily obtained without recourse to a buffering gas or synchronizing electron injection with a specific phase of an RF field. The mass spectra produced with the modified instrument appear in all respects (other than resolution and mass accuracy, which were limited by the mass spectrometer used) to be at least as good for purposes of peptide identification as those recorded with Fourier transform ion cyclotron resonance (FT ICR) instruments; however, the effort and time to produce the mass spectra were much less than required to produce their FT ICR counterparts. The cell's design and compact construction should allow it to be incorporated at relatively little cost into virtually any type of tandem mass spectrometer, for example, triple quadrupole, hybrid quadrupole ion trap, hybrid quadrupole time-of-flight, or even FT-ICR.

Rapid Communications in Mass SpectrometryVolume 22, Issue 19 p. 3087-3088 Letter to the Editor Electron capture dissociation in a linear radiofrequency-free magnetic cell Valery G. Voinov, Corresponding Author Valery G. Voinov [email protected] Department of Chemistry, Oregon State University, Corvallis, OR 97331, USA Pacific Institute of Bioorganic Chemistry, Vladivostok 690022, RussiaDepartment of Chemistry, Oregon State University, Corvallis, OR 97331, USA.Search for more papers by this authorMax L. Deinzer, Max L. Deinzer Department of Chemistry, Oregon State University, Corvallis, OR 97331, USASearch for more papers by this authorDouglas F. Barofsky, Douglas F. Barofsky Department of Chemistry, Oregon State University, Corvallis, OR 97331, USASearch for more papers by this author Valery G. Voinov, Corresponding Author Valery G. Voinov [email protected] Department of Chemistry, Oregon State University, Corvallis, OR 97331, USA Pacific Institute of Bioorganic Chemistry, Vladivostok 690022, RussiaDepartment of Chemistry, Oregon State University, Corvallis, OR 97331, USA.Search for more papers by this authorMax L. Deinzer, Max L. Deinzer Department of Chemistry, Oregon State University, Corvallis, OR 97331, USASearch for more papers by this authorDouglas F. Barofsky, Douglas F. Barofsky Department of Chemistry, Oregon State University, Corvallis, OR 97331, USASearch for more papers by this author First published: 04 September 2008 https://doi.org/10.1002/rcm.3709Citations: 26Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat No abstract is available for this article. REFERENCES 1 Cooper HJ, Hakansson K, Marshall AG. Mass Spectrom. Rev. 2005; 24: 201. 2 Bakhtiar R, Guan Z. Biotechnol. Lett. 2006; 28: 1047. 3 Baba T, Hashimoto Y, Hasegawa H, Hirabayashi A, Waki I. Anal. Chem. 2004; 76: 4263; Satake H, Hasegawa H, Hirabayashi A, Hashimoto Y, Baba T, Anal. Chem. 2007; 79: 8755. 4 Silivra OA, Kjeldsen F, Ivonin IA, Zubarev R. J. Am. Soc. Mass Spectrom. 2005; 16: 22. 5 Ding L, Brancia L. Anal. Chem. 2006; 78: 1995. 6 Ji H, Voinov V, Deinzer ML, Barofsky DF. ECD in a linear RF-field without buffer gas. Proc. 55th ASMS Conf. Mass Spectrometry and Allied Topics, Indianapolis, Indiana: 2007; 1381 (WPE-084). 7 Campbell P. Permanent Magnet Materials and Their Application. Cambridge University Press: Cambridge, 1994; 201–202. 8 Budnik BA, Nielsen ML, Olsen JV, Haselmann KF, Hörth P, Haehnel W, Zubarev RA. Int. J. Mass Spectrom. 2002; 219: 283. 9 Leymarie N, Costello CE, O'Connor PB. J. Am. Soc. Mass. Spectrom. 2003; 125: 8949. Citing Literature Volume22, Issue1915 October 2008Pages 3087-3088 ReferencesRelatedInformation

The retinoid X receptor (RXR) is a ligand-activated transcription factor that plays an important role in growth and development and the maintenance of cellular homeostasis. A thermodynamic ultraviolet circular dichroism, tryptophan fluorescence and ligand binding activity with guanidine as a chemical denaturant are consistent with a two step mechanism. The dimeric LBD equilibrates with a monomeric intermediate (Delta G(0) (H(2)O) equal to 8.3 kcal/mol) that is in equilibrium with the unfolded state (Delta G(0)(H(2)O) equal to 2.8 kcal/mol). The intermediate was characterized by analytical ultracentrifugation, spectroscopy, and collisional fluorescence quenching, which imply that the monomeric intermediate maintains a high degree, but not all, of native secondary structure. Although intrinsic fluorescence from native and intermediate suggests little change in tryptophan environments, fluorescence intensities from fluorescein reporter groups differ significantly between the two structures. Analysis of the collisional quenching results imply that the intermediate is characterized by tryptophans with increased accessibility to small solutes and less overall compactness than the native protein. (C) 2009 Elsevier B.V. All rights reserved.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Comprehensive mass spectral fragmentation patterns have been established for sequencing chromatographically isolated A-type proanthocyanidins (PAs) using electrospray ionization tandem mass spectrometry (ESI-MS(n)) in the positive ion mode similar to those used for sequencing previously reported B-type PAs. Sequence-identifying fragmentations for A-type PAs include heterocyclic ring fission (HRF), retro-Diels-Alder (RDA) fission, benzofuran-forming (BFF) fission, and quinone methide (QM) fission. There is commonality in fragmentation patterns between A-type and B-type PAs, but distinguishing features in the mass spectral patterns between the two classes include 2-Da mass differences in the pseudo molecular ions, the propensity for the A-type PAs to undergo QM fissions and yield bis-quinoid ions as opposed to mono-quinoid ions in the upper unit of the sequence, and the reluctance of A-type linkages to undergo RDA, BFF, and BFF/H(2)O fissions from the upper unit. The positions of one or more A-type (C2-->O-->C7') ether linkages have been located in sequences of PAs ranging in chain lengths of two to five monomer units using ESI-MS(n) data. Using the fragmentation information from ESI-MS(n) experiments, a total of 17 PAs were structurally sequenced by systematic real time ESI-MS(n). Among them ten A-type and six B-type hop PAs are reported here for the first time.

Resonant electron capture by C2Cl4, C2HCl3, cis-, trans- and geminal-C2H2Cl2, C2HBr3, cis- and trans-C2H2Br2 and C2H3Br has been studied. A new method for the measurements of absolute electron attachment cross-sections based on the interface of a gas-chromatography and a reflectron-time-of-flight-mass spectrometer has been developed and the method was applied for these compounds.

Seven highly polar trisulfated triterpene glycosides belonging to the frondoside A7 group have been isolated from the North Atlantic sea cucumber Cucumaria frondosa. The structures of five new glycosides, frondosides A7-1 (1), A7-2 (2), A7-3 (3), A7-4 (4), and isofrondoside C (5) were elucidated, three of which contained lanostane aglycons without a lactone-ring. Three pairs of the glycosides proved to be isomers by virture of the positions of double bonds in the aglycons nuclei; two pairs of the glycosides differed from each other by the character of the oxygen functionality at C-22. The results from these studies provided the basis for postulating the biosynthetic pathways of norlanostane glycosides in the sea cucumber.Key words: Cucumaria frondosa, sea cucumbers, frondosides, triterpene glycosides.

Manual and automated solvent-free mini-ball mill (MBM) matrix-assisted laser desorption/ionization (MALDI) analysis of mixtures of β-amyloid peptides (1–11), (33–42), (1–42) and non-β-amyloid component of Alzheimer’s disease peptide yielded interpretable spectra for all of the peptides present regardless of their relative amounts in the samples. This was not the case for solvent-based MALDI analysis using traditional acidic aqueous/organic solvent conditions, which resulted in severe over-representation of hydrophilic peptide (1–11) and provided no spectra for insoluble amphiphilic peptide (1–42) even when present at 50% relative molar amount. Less accurate representation of components in mixtures by the traditional method appears to be a combination of poor dissolution of peptides in the solvent and preferential ionization of more hydrophilic peptides in the mixture. Consequently, only MBM provided a complete tryptic map of β-amyloid (1–42) compared to 67% coverage by traditional MALDI. Acetonitrile (0.1% TFA) led to improved coverage only at a 50% molar ratio of peptide (1–42), but also to a side product of (1–42), Met oxidation (amino acid 35), a phenomenon not observed in MBM MALDI analysis. Traditional MALDI analysis resulted in over-representation of hydrophilic soluble β-amyloid (1–11) in defined mixtures and autoproteolytic peptides of trypsin. In contrast, over-representation and under-representation were less pronounced in solvent-free MALDI in all of the investigated cases. Analysis of defined peptide and tryptic peptide mixtures showed that MBM MALDI yielded greater qualitative reliability, which also improved quantitative response relative to the solvent-based approach.