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Electrospray Ion Trap Mass Spectrometry (electrospray + ion_trap_mass_spectrometry)

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Chemistry	100%

Selected Abstracts

Determination of cylindrospermopsin in freshwaters and fish tissue by liquid chromatography coupled to electrospray ion trap mass spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2009
Pasquale Gallo
Cylindrospermopsin (CYN) is a toxic alkaloid-like compound produced by some strains of cyanobacteria, procariotic organisms occurring in water blooms, observed worldwide in eutrophic lakes and drinking water reservoirs. Methods for determination of CYN in freshwater and fish muscle by liquid chromatography coupled to electrospray ion trap mass spectrometry are herein described. The performances of both methods are reported; ion trap LC/ESI-MS/MS resulted highly selective and reliable in unambiguous identification of CYN, based on monitoring the precursor ion and three product ions. The methods developed showed satisfactory mean recoveries (higher than 63.6%) and relative standard deviations, ranging from 5.8 to 9.8%. The limits of quantification at 0.10,ng/mL in freshwaters and 1.0,ng/g in fish muscle, respectively, allow for determination of CYN also in early contamination stages. Ion trap LC/ESI-MS/MS was successfully applied to the identification and quantification of CYN in water and cyanobacteria extracts from Lake Averno, near Naples, representing the first case of contamination described in southern Italy. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Tandem electrospray mass spectrometric studies of proton and sodium ion adducts of neutral peptides with modified N- and C-termini: synthetic model peptides and microheterogeneous peptaibol antibiotics

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2006
Varatharajan Sabareesh
The fragmentations of [M+H]+ and [M+Na]+ adducts of neutral peptides with blocked N- and C-termini have been investigated using electrospray ion trap mass spectrometry. The N-termini of these synthetically designed peptides are blocked with a tertiarybutyloxycarbonyl (Boc) group, and the C-termini are esterified. These peptides do not possess side chains that are capable of complexation and hence the backbone amide units are the sole sites of protonation and metallation. The cleavage patterns of the protonated peptides are strikingly different from those of sodium ion adducts. While the loss of the N-terminal blocking group occurs quite readily in the case of MS/MS of [M+Na]+, the cleavage of the C-terminal methoxy group seems to be a facile process in the case of MS/MS of [M+H]+. Fragmentation of the protonated adducts yields only bn ions, while yn and an ions are predominantly formed from the fragmentation of sodium ion adducts. The an ions arising from the fragmentation of [M+Na]+ lack the N-terminal Boc group (and are here termed an* ions). MS/MS of [M+Na]+ species also yields bn ions of substantially lower intensities that lack the N-terminal Boc group (bn*). A similar distinction between the fragmentation patterns of proton and sodium ion adducts is observed in the case of peptides possessing an N-terminal acetyl group. An example of the fragmentation of the H+ and Na+ adducts of a naturally occurring peptaibol from a Trichoderma species confirms that fragmentation of these two ionized species yields complementary information, useful in sequencing natural peptides. Inspection of the isotopic pattern of bn ions derived from [M+H]+ adducts of peptaibols provided insights into the sequences of microheterogeneous samples. This study reveals that the combined use of protonated and sodium ion adducts should prove useful in de novo sequencing of peptides, particularly of naturally occurring neutral peptides with modified N- and C-termini, for example, peptaibols. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Reactivity of the NS2/3(907,1206)ASK4 protein with ,-mercaptoethanol studied by electrospray ion trap mass spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2002
Laura Orsatti
The present work reports a mass spectrometric investigation of the NS2/3 protein, a protease from hepatitis C virus (HCV). During routine protein manipulation, in the presence of 100,mM ,-mercaptoethanol and under denatured conditions, the protein was unexpectedly modified at its cysteine residues, and the increased molecular weight corresponded to one molecule of ,-mercaptoethanol bound. The modified protein, once refolded, was found to be less active than the unmodified one. The aim of this work was to investigate whether the reactivity of cysteines with ,-mercaptoethanol involves one specific, highly reactive residue of the sequence, or if the modification is a random process. Liquid chromatography (LC) coupled on-line with an electrospray ion trap mass spectrometer was used to identify the modification sites. It was found that five cysteines out of nine had reacted with ,-mercaptoethanol, none of them showing a significantly higher reactivity than the others. 95% of sequence coverage was obtained. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Model peptide-based system used for the investigation of metal ions binding to histidine-containing polypeptides

BIOPOLYMERS, Issue 6 2010
Manuela Murariu
Abstract The reaction of histidine-containing polypeptides with toxic and essential metals and the molecular mechanism of complexation has yet to be determined, particularly with respect to the conformational changes of the interacting macromolecules. Therefore, a system of oligopeptides containing histidine residues in various positions of Ala or Gly sequences has been designed and used in heavy metal comparatively binding experiments. The role of spacing residues (Gly and Ala repeats) in selecting the various conformations was investigated. The newly synthesized peptides and metal ion adducts have been characterized by Fourier transform infrared spectroscopy (FTIR) as well as electrospray ion trap mass spectrometry (ESI,MS) and circular dichroism (CD). The analysis of CD-spectra of the four peptides in water revealed that the secondary structure depends much on the position of each amino acid in the peptide backbone. Our peptides system reveals various binding mechanisms of metal ions to peptides depending on the position of histidine residue and the corresponding conformations of Ala or Gly sequences. Biological and medical consequences of conformational changes of metal-bound peptides are further discussed. Thus, the binding of heavy metals to four peptides may serve as a model system with respect to the conformational consequences of the metal addition on the amino acid repeats situated in prion protein. © 2010 Wiley Periodicals, Inc. Biopolymers 93:497,508, 2010. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source]