Effects of Select Anions from the Hofmeister Series on the Gas-Phase Conformations of Protein Ions Measured with Traveling-Wave Ion Mobility Spectrometry/Mass Spectrometry

Merenbloom, Samuel I.; Flick, Tawnya G.; Daly, Michael; Williams, Evan R.

doi:10.1007/s13361-011-0238-1

Cited by 38 publications

(46 citation statements)

References 83 publications

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“…The more unfolded conformations of the intermediate charge states in these TWIMS experiments are similar to those observed when ions are heated in the source region [56] or within an RF-trap prior to injection to a drift tube [12]. The greater activation that occurs in TWIMS compared to static-field IMS when gentle conditions are used complicate the comparison of these data for the purpose of calibrating collision cross sections [58]. …”

Section: Resultsmentioning

confidence: 82%

How Hot are Your Ions in TWAVE Ion Mobility Spectrometry?

Merenbloom

Flick

Williams

2011

J. Am. Soc. Mass Spectrom.

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135

167

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Effective temperatures of ions during traveling wave ion mobility spectrometry (TWIMS) analysis were measured using singly protonated leucine enkephalin dimer as a chemical thermometer by monitoring dissociation of the dimer into monomer, as well as the subsequent dissociation of monomer into a-, b-, and y-ions, as a function of instrumental parameters. At fixed helium cell and TWIMS cell gas flow rates, the extent of dissociation does not vary significantly with either the wave velocity or wave height, except at low (<500 m/s) wave velocities that are not commonly used. Increasing the flow rate of nitrogen gas into the TWIMS cell and decreasing the flow rate of helium gas into the helium cell resulted in greater dissociation. However, the mobility distributions of the fragment ions formed by dissociation of the dimer upon injection into the TWIMS cell are nearly indistinguishable from those of fragment ions formed in the collision cell prior to TWIMS analysis for all TWIMS experiments. These results indicate that heating and dissociation occur when ions are injected into the TWIMS cell, and that the effective temperature subsequently decreases to a point at which no further dissociation is observed during the TWIMS analysis. An upper limit to the effective ion temperature of 449 K during TWIMS analysis is obtained at a helium flow rate of 180 mL/min, TWIMS flow rate of 80 mL/min and traveling wave height of 40 V, which is well below previously reported values. Effects of ion heating in TWIMS on gas-phase protein conformation are presented.

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Section: Resultsmentioning

confidence: 82%

How Hot are Your Ions in TWAVE Ion Mobility Spectrometry?

Merenbloom

Flick

Williams

2011

J. Am. Soc. Mass Spectrom.

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135

167

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“…This indicates that the partially sodiated ions are even more compact than the compact conformers of the fully protonated ions with the same charge state formed from water or ammonium acetate. Nonspecific cation adduction to gaseous protein ions typically results in compaction of structure compared to the protonated form, even when the ions are formed from the same solution [64]. The CD results show that the protein conformation in aqueous solutions without salts added is different than in ammonium acetate solutions.…”

Section: Resultsmentioning

confidence: 99%

Effects of Cations on Protein and Peptide Charging in Electrospray Ionization from Aqueous Solutions

Susa

Mortensen

Williams

2014

J. Am. Soc. Mass Spectrom.

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The effects of eight different cations with ionic radii between 69 and 337 pm on the charging of peptides and proteins with electrospray ionization from aqueous acetate salt solutions are reported. Significant adduction occurs for all cations except NH4+, and the average protein charge is lower when formed from solutions containing salts compared to solutions without salts added. Circular dichroism and ion mobility results show the protein conformations are different in pure water compared to salt solutions, which likely affects the extent of charging. The average charge of protein and peptide ions formed from solutions with Li+ and Cs+, which have Gibbs solvation free energies (GSFEs) that differ by 225 kJ/mol, is similar. Lower charge states are typically formed from solutions with tetramethylammonium and tetraethylammonium that have lower GSFE values. Loss of the larger cations that have the lowest GSFEs is facile when adducted protein ions are collisionally activated resulting in the formation of lower analyte charge states. This reaction pathway provides a route to produce abundant singly protonated protein ions under native mass spectrometry conditions. The average protein and peptide charge with NH4+ is nearly the same as that with Rb+ and K+, cations with similar GSFE and ionic radii. This indicates that proton transfer from NH4+ to proteins plays an insignificant role in the extent of protein charging in native mass spectrometry.

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“…6,7,19,21–23 The key variables affecting ion motion in TWIMS are the TW amplitude, the TW velocity, and the operating pressure (as well as temperature). 2,6,19,24 The ability of ions to “keep up” with a TW depends on their mobilities; 6,25 higher mobility ions tend to move more closely to the TW speed (and stack up at the wavefront without separation in “traveling traps”, sometimes referred to as “ion surfing”), whereas lower mobility ions tend to slip behind the TW (i.e., be passed by waves) more often. 20,21 Ions with speeds lower than the TW have longer drift times and are dispersed to different degrees, thus achieving ion mobility separations.…”

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confidence: 99%

Characterization of Traveling Wave Ion Mobility Separations in Structures for Lossless Ion Manipulations

et al. 2015

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We report on the development and characterization of a traveling wave (TW)-based Structures for Lossless Ion Manipulations (TW-SLIM) module for ion mobility separations (IMS). The TW-SLIM module uses parallel arrays of rf electrodes on two closely spaced surfaces for ion confinement, where the rf electrodes are separated by arrays of short electrodes, and using these TWs can be created to drive ion motion. In this initial work, TWs are created by the dynamic application of dc potentials. The capabilities of the TW-SLIM module for efficient ion confinement, lossless ion transport, and ion mobility separations at different rf and TW parameters are reported. The TW-SLIM module is shown to transmit a wide mass range of ions (m/z 200–2500) utilizing a confining rf waveform (~1 MHz and ~300 Vp-p) and low TW amplitudes (<20 V). Additionally, the short TW-SLIM module achieved resolutions comparable to existing commercially available low pressure IMS platforms and an ion mobility peak capacity of ~32 for TW speeds of <210 m/s. TW-SLIM performance was characterized over a wide range of rf and TW parameters and demonstrated robust performance. The combined attributes of the flexible design and low voltage requirements for the TW-SLIM module provide a basis for devices capable of much higher resolution and more complex ion manipulations.

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Effects of Select Anions from the Hofmeister Series on the Gas-Phase Conformations of Protein Ions Measured with Traveling-Wave Ion Mobility Spectrometry/Mass Spectrometry

Cited by 38 publications

References 83 publications

How Hot are Your Ions in TWAVE Ion Mobility Spectrometry?

How Hot are Your Ions in TWAVE Ion Mobility Spectrometry?

Effects of Cations on Protein and Peptide Charging in Electrospray Ionization from Aqueous Solutions

Characterization of Traveling Wave Ion Mobility Separations in Structures for Lossless Ion Manipulations

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