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Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (electrospray + ionization_fourier_transform_ion_cyclotron_resonance_mass_spectrometry)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

Evaluation of the metal binding properties of a histidine-rich fusogenic peptide by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 11 2003
Andrea Sinz
Abstract Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS) was used to investigate metal ion interactions of the 18 amino acid peptide fragment B18 (LGLLLRHLRHHSNLLANI), derived from the membrane-associated protein bindin. The peptide sequence B18 represents the minimal membrane-binding motif of bindin and resembles a putative fusion peptide. The histidine-rich peptide has been shown to self-associate into distinct supramolecular structures, depending on the presence of Zn2+ and Cu2+. We examined the binding of B18 to the metal ions Cu2+, Zn2+, Mg2+, Ca2+, Mn2+ and La3+. For Cu2+, we compared the metal binding affinities of the wild-type B18 peptide with those of its mutants in which one, two or three histidine residues have been replaced by serines. Upon titration of B18 with Cu2+ ions, we found sequential binding of two Cu2+ ions with dissociation constants of ,34 and ,725 µM. Mutants of B18, in which one histidine residue is replaced by serine, still exhibit sequential binding of two copper ions with affinities for the first Cu2+ ion comparable to that of wild-type B18 peptide, but with a greatly reduced affinity for the second Cu2+ ion in mutants H112S and H113S. For mutants in which two histidines are replaced by serines, the affinity for the first Cu2+ ion is reduced ,3,10 times in comparison with B18. The mutant in which all three histidine residues are replaced by serines exhibits an ,14-fold lower binding for the first Cu2+ ion compared with B18. For the other metal ions under investigation (Zn2+, Mg2+, Ca2+, Mn2+ and La3+), a modest affinity to B18 was detected binding to the peptide in a 1 : 1 stoichiometry. Our results show a high affinity of the wild-type fusogenic peptide B18 for Cu2+ ions whereas the Zn2+ affinity was found to be comparable to that of other di- and trivalent metal ions. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Gas phase isomeric differentiation of oleanolic and ursolic acids associated with heptakis-(2,6-di- O -methyl)-,-cyclodextrin by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 4 2010
Zhan Yu
Abstract Oleanolic acid (OA) and ursolic acid (UA) are isomeric triterpenoid compounds with similar pharmaceutical properties. Usually, modern chromatographic and electrophoretic methods are widely utilized to differentiate these two compounds. Compared with mass spectrometric (MS) methods, these modern separation methods are both time- and sample-consuming. Herein, we present a new method for structural differentiation of OA and UA by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with the association of heptakis-(2,6-di- O -methyl)-,-cyclodextrin (DM-,-CD). Exact MS and tandem MS (MS/MS) data showed that there is no perceptible difference between OA and UA, as well as their ,-cyclodextrin and ,-cyclodextrin complexes. However, there is a remarkable difference in MS/MS spectra of DM-,-CD complexes of OA and UA. The peak corresponding to the neutral loss of a formic acid and a water molecule could only be observed in the MS/MS spectrum of the complex of DM-,-CD : OA. Molecular modeling calculations were also employed to further investigate the structural differences of DM-,-CD : OA and DM-,-CD : UA complexes. Therefore, by employing DM-,-CD as a reference reagent, OA and UA could be differentiated with purely MS method. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Evaluation of the metal binding properties of a histidine-rich fusogenic peptide by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 11 2003
Andrea Sinz
Abstract Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS) was used to investigate metal ion interactions of the 18 amino acid peptide fragment B18 (LGLLLRHLRHHSNLLANI), derived from the membrane-associated protein bindin. The peptide sequence B18 represents the minimal membrane-binding motif of bindin and resembles a putative fusion peptide. The histidine-rich peptide has been shown to self-associate into distinct supramolecular structures, depending on the presence of Zn2+ and Cu2+. We examined the binding of B18 to the metal ions Cu2+, Zn2+, Mg2+, Ca2+, Mn2+ and La3+. For Cu2+, we compared the metal binding affinities of the wild-type B18 peptide with those of its mutants in which one, two or three histidine residues have been replaced by serines. Upon titration of B18 with Cu2+ ions, we found sequential binding of two Cu2+ ions with dissociation constants of ,34 and ,725 µM. Mutants of B18, in which one histidine residue is replaced by serine, still exhibit sequential binding of two copper ions with affinities for the first Cu2+ ion comparable to that of wild-type B18 peptide, but with a greatly reduced affinity for the second Cu2+ ion in mutants H112S and H113S. For mutants in which two histidines are replaced by serines, the affinity for the first Cu2+ ion is reduced ,3,10 times in comparison with B18. The mutant in which all three histidine residues are replaced by serines exhibits an ,14-fold lower binding for the first Cu2+ ion compared with B18. For the other metal ions under investigation (Zn2+, Mg2+, Ca2+, Mn2+ and La3+), a modest affinity to B18 was detected binding to the peptide in a 1 : 1 stoichiometry. Our results show a high affinity of the wild-type fusogenic peptide B18 for Cu2+ ions whereas the Zn2+ affinity was found to be comparable to that of other di- and trivalent metal ions. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Characterization of a peptide family from the skin secretion of the Middle East Tree Frog Hyla savignyi by composition-based de novo sequencing

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2010
Markus Langsdorf
A new tryptophyllin-like peptide family was found in the skin secretion of the tree frog Hyla savignyi. Peptides were characterized by database-independent sequencing strategies and specific ion fragmentation features were investigated. Skin secretions from specimens of Hyla savignyi were collected by mild electrical stimulation. Peptides were separated by reversed-phase nano-high-performance liquid chromatography (nanoHPLC) and mass spectra were acquired online by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). Peptides were characterized by manual de novo sequencing and by composition-based sequencing (CBS), appearing mostly as C-terminal free acids and as their acid amide analogs. Amide peptides yielded lower intensities of y-type ions after collision-induced dissociation (CID) than their acid analogs. A mechanism of internal b-ion formation (positive ion mode) and of CO2 elimination (negative ion mode) is proposed. We also exemplified phenomena such as the proline effect and formation of non-direct sequence ions after sequence rearrangements. The occurrence of rearrangement products, of internal ions and of the proline effect made the CID spectra highly complex. CBS analysis nevertheless resulted in successful and highly reliable sequence analysis. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Molecular mass ranges of coal tar pitch fractions by mass spectrometry and size-exclusion chromatography

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2009
F. Karaca
A coal tar pitch was fractionated by solvent solubility into heptane-solubles, heptane-insoluble/toluene-solubles (asphaltenes), and toluene-insolubles (preasphaltenes). The aim of the work was to compare the mass ranges of the different fractions by several different techniques. Thermogravimetric analysis, size-exclusion chromatography (SEC) and UV-fluorescence spectroscopy showed distinct differences between the three fractions in terms of volatility, molecular size ranges and the aromatic chromophore sizes present. The mass spectrometric methods used were gas chromatography/mass spectrometry (GC/MS), pyrolysis/GC/MS, electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS) and laser desorption time-of-flight mass spectrometry (LD-TOFMS). The first three techniques gave good mass spectra only for the heptane-soluble fraction. Only LDMS gave signals from the toluene-insolubles, indicating that the molecules were too involatile for GC and too complex to pyrolyze into small molecules during pyrolysis/GC/MS. ESI-FTICRMS gave no signal for toluene-insolubles probably because the fraction was insoluble in the methanol or acetonitrile, water and formic acid mixture used as solvent to the ESI source. LDMS was able to generate ions from each of the fractions. Fractionation of complex samples is necessary to separate smaller molecules to allow the use of higher laser fluences for the larger molecules and suppress the formation of ionized molecular clusters. The upper mass limit of the pitch was determined as between 5000 and 10,000,u. The pitch asphaltenes showed a peak of maximum intensity in the LDMS spectra at around m/z 400, in broad agreement with the estimate from SEC. The mass ranges of the toluene-insoluble fraction found by LDMS and SEC (400,10,000,u with maximum intensity around 2000,u by LDMS and 100,9320,u with maximum intensity around 740,u by SEC) are higher than those for the asphaltene fraction (200,4000,u with maximum intensity around 400,u by LDMS and 100,2680,u with maximum intensity around 286,u by SEC) and greater than values considered appropriate for petroleum asphaltenes (300,1200,u with maximum intensity near 700,u). Copyright © 2009 John Wiley & Sons, Ltd. [source]