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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 detailEffective temperature of ions in traveling wave ion mobility spectrometry
Morsa, Denis ULg; Gabelica, Valérie ULg; De Pauw, Edwin ULg

in Analytical Chemistry (2011), 83(14), 5775-5782

Traveling wave ion mobility spectrometers (TW IMS) operate at significantly higher fields than drift tube ion mobility spectrometers. Here we measured the fragmentation of the fragile p ... [more ▼]

Traveling wave ion mobility spectrometers (TW IMS) operate at significantly higher fields than drift tube ion mobility spectrometers. Here we measured the fragmentation of the fragile p-methoxybenzylpyridinium ion inside the TW ion mobility cell of the first-generation SYNAPT HDMS spectrometer. The ion’s vibrational internal energy was quantified by a vibrational effective temperature Teff,vib, which is the mean temperature of the ions inside the cell that would result in the same fragmentation yield as observed experimentally. Significant fragmentation of the probe ion inside the TW IMS cell was detected, indicating that field heating of the ions takes place in TW IMS. For typical small molecule IMS conditions, Teff,vib = 555 ± 2 K. The variations of the effective temperature were studied as a function of the IMS parameters, and we found that Teff,vib decreases when the wave height decreases, when the pressure increases, or when the wave speed increases. The energy transfer efficiency of argon is higher than for He, N2 or CO2. Teff,vib being directly related to the ion speed inside the TW IMS, our results also provide new insight on the ion movement in TW IMS. We also discuss the influence of field heating of ions for calibration and structural studies in TW IMS. [less ▲]

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See detailInternal energy content of ions in a travelling wave ion guide
Morsa, Denis ULg; Gabelica, Valérie ULg; Rosu, Frédéric ULg et al

Conference (2010)

Travelling wave ion guides (TWIGs) separate of ions according to their mobility and, at constant charge, according to their shape. The ion mobility separation itself should not modify the shape of the ... [more ▼]

Travelling wave ion guides (TWIGs) separate of ions according to their mobility and, at constant charge, according to their shape. The ion mobility separation itself should not modify the shape of the systems investigated. It was recently suggested by Shvartsburg et al. that the higher fields used in TWIGs than in traditional drift tubes would cause significant heating of the ions. We present a quantitative analysis of the amount of internal energy imparted to ions as they are separated in TWIGs. Benzylpyridinium ions were chosen as “thermometer” ions. Based on arrival time distributions, the fragment ion population is separated as a function of the place of formation: before, in, or after the TWIG. Fragmentation all along the TWIG was observed. The roles of the travelling wave’s voltage, speed, and of the gas nature and pressure will be discussed in detail as well of the consequences on instruments performances. [less ▲]

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