References of "Morsa, Denis"
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See detailEnergetics and Structural Characterization of Isomers Using Ion Mobility and Gas-phase H/D Exchange: Learning from Lasso Peptides
Hanozin, Emeline ULg; Morsa, Denis ULg; De Pauw, Edwin ULg

in Proteomics (2015), early view

State-of-the-art characterization of proteins using mass spectrometry namely relies on fragmentation methods which allows exploring featured dissociative reaction pathways. These pathways are often ... [more ▼]

State-of-the-art characterization of proteins using mass spectrometry namely relies on fragmentation methods which allows exploring featured dissociative reaction pathways. These pathways are often initiated by a series of potentially informative mass-constant conformational changes that are nonetheless frequently overlooked by lack of adequate investigation techniques. In the present study, we propose a methodology to readily address both structural and energetic aspects of stereoisomerization reactions using ion mobility coupled with mass spectrometry. To this end, a commercial spectrometer was used as a reactor comprising an energy resolved collisional activation step intended at promoting controlled conformational changes and a structural assignment step dedicated to the identification of the generated isomers. This identification relies on ion mobility and other on-line coupled techniques, namely an originally designed gas-phase H/D exchange experiment. We here apply this methodology to characterize the isomerization kinetics of capistruin, a 19-residue long lasso-folded peptide. We expect this approach to bring insights into the physical origin of global dissociation thresholds monitored in tandem mass spectrometry experiments and to set a promising basis for quantitative investigations of the stability of different molecular folds. [less ▲]

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See detailIs the natural shape of ions in the gas phase spherical ? The allegory of the cave (Plato) applied in mass spectrometry
Far, Johann ULg; Haler, Jean ULg; Kune, Christopher ULg et al

Conference (2015, May 13)

The transfer of ions from solution to gas phase is a critical step to produce « native species ». Coming from a highly solvating medium, ionic species will tend to find new equilibrium conformations in ... [more ▼]

The transfer of ions from solution to gas phase is a critical step to produce « native species ». Coming from a highly solvating medium, ionic species will tend to find new equilibrium conformations in the gas phase. The pathway to reach the thermodynamically stable conformation(s) involves crossing potential barriers according to the type of interactions involved. When these barriers are too high compared to the internal energy of the ions, it may result in a “partial memory” (as structural preservation) of the conformation in solution. In order to evaluate the effect of the solvent evaporation and of the various collision processes encountered by the ions in the mass spectrometer we based our strategy on the determination of deviations from a spherical shape, supposed to be the natural state of ions in the gas phase. [less ▲]

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See detailIon mobility-mass spectrometry to perform structural classifications of disulfide-bridged-peptides
Massonnet, Philippe ULg; Upert, Gregory; Morsa, Denis ULg et al

Poster (2014, November)

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See detailDissociation Pathways of Benzylpyridinium “Thermometer” Ions Depend on the Activation Regime: An IRMPD Spectroscopy Study
Morsa, Denis ULg; Gabelica, Valérie ULg; Rosu, Frédéric et al

in Journal of Physical Chemistry Letters (2014), 5

The dissociation of benzylpyridinium “thermometer” ions is widely used to calibrate the internal energy of ions produced in mass spectrometry. The fragmentation mechanism is usually believed to yield a ... [more ▼]

The dissociation of benzylpyridinium “thermometer” ions is widely used to calibrate the internal energy of ions produced in mass spectrometry. The fragmentation mechanism is usually believed to yield a benzylium cation, although recent studies suggest the possibility of a rearrangement leading to the tropylium isomer, which would compromise the accuracy of energy calibrations. In this study, we used IRMPD spectroscopy to probe the dissociation pathways of the p-(tert-butyl)- benzylpyridinium ion. Our results show that the formation of both benzylium and tropylium products is feasible depending on the activation regime and on the reaction time scale. Varying the trapping delays in the hexapole gives insight into a rearrangement mechanism occurring through consecutive reactions with an isomerization from benzylium to tropylium. Our work provides experimental validations for the established calibration procedure and highlights the adequacy of IRMPD spectroscopy to qualitatively resolve gas-phase rearrangement kinetics. [less ▲]

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See detailPolymer topology revealed by ion mobility coupled with mass spectrometry
Morsa, Denis ULg; Defize, Thomas ULg; Dehareng, Dominique ULg et al

in Analytical Chemistry (2014), 86(19), 96939700

Hyperbranched and star shaped polymers have raised tremendous interests because of their unusual structural and photochemical properties which provide them potent applications in various domains, namely ... [more ▼]

Hyperbranched and star shaped polymers have raised tremendous interests because of their unusual structural and photochemical properties which provide them potent applications in various domains, namely in the biomedical field. In this context, the development of adequate tools aiming to probe particular three-dimensional features of such polymers is of crucial importance. In this present work, ion mobility coupled with mass spectrometry was used to experimentally derive structural information related to cationized linear and star-shaped poly-ε-caprolactones as a function of their charge state and chain length. Two major conformations were observed and identified using theoretical modeling: (1) near spherical conformations whose size is invariant with the polymer topology for long and lightly charged chains and (2) elongated conformations whose size varies with the polymer topology for short and highly charged chains. These conformations were further confirmed by collisional activation experiments based on the ejection thresholds of the coordinated cations that vary according to the elongation amplitude of the polymer chains. Finally, a comparison between solution and gas-phase conformations highlights a compaction of the structure with a loss of specific chain arrangements during the ionization and desolvation steps of the electrospray process, fueling the long-time debated question related to the preservation of the analyte structure during the transfer into the mass spectrometer. [less ▲]

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See detailProbing the conformational changes during desolvation of ions using orthogonal mobility methods (CE-IMS)
Far, Johann ULg; Kune, Christopher ULg; Delvaux, Cédric ULg et al

Poster (2014, April 08)

The transfer of ions from the solution to the gas phase is a critical step to produce « native species ». Coming from a highly solvating medium, ionic species will tend to find a new equilibrium ... [more ▼]

The transfer of ions from the solution to the gas phase is a critical step to produce « native species ». Coming from a highly solvating medium, ionic species will tend to find a new equilibrium conformation in the gas phase. The pathway to reach the thermodynamically stable conformation involves crossing potential barriers of different heights. When these barriers are too high compared to the internal energy of the ions, it will result in “partial memories” (as structural preservation) of the conformation in solution. In order to evaluate the effect of the solvent evaporation and of the various collision processes encountered by the ions in the mass spectrometer. The strategy consists in comparing in a single experiment the shape of the ions in solution and in the gas phase. Data are obtained by coupling capillary electrophoresis with Ion Mobility Mass Spectrometry. Drift times in solution and in the gas phase are directly compared. Deviations from their correlation points out changes in folding upon desolvatation. Preliminary results show that among peptides issued from tryptic digest of BSA some of them clearly change their conformation during desolvatation. This work intends to evaluate the extent of conformational “memory” of the ions of different nature for best experimental condition allowing “native mass spectrometry”. [less ▲]

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See detailPolymer architecture revealed by ion mobility - mass spectrometry
Morsa, Denis ULg; Defize, Thomas ULg; Dehareng, Dominique et al

Conference (2014, April)

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