Evaluation of calculated negative mode ion mobilities of small molecules in air

Ion mobility spectrometry is a well-known technique employed for the detection and analysis of gaseous substances. In pharmaceutical applications, it is furthermore used for structural analysis of compounds, especially in combination with mass spectrometry. In this field, the comparison of calculated collision cross sections and ion mobilities of theoretic model compounds with experimental values measured with ion mobility spectrometers helps to determine the compound’s structure. For positive mode ion mobility spectrometry, the calculated mobilities using the Trajectory Method show in general a deviation of 10% or less from experimental values. In this article, it was analyzed how well the calculated values reproduce the experimental values obtained with negative mode ion mobility spectrometry including symmetric and asymmetric analyte clusters. Furthermore, the influence of four different partial charge models on the results was investigated.

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Correcting the fundamental ion mobility equation for field effects

The Analyst ◽

10.1039/c6an01353h ◽

2016 ◽

Vol 141 (23) ◽

pp. 6396-6407 ◽

Cited By ~ 15

Author(s):

William F. Siems ◽

Larry A. Viehland ◽

Herbert H. Hill

Keyword(s):

Momentum Transfer ◽

Ion Mobility Spectrometry ◽

Cross Sections ◽

Ion Mobility ◽

Collision Frequency ◽

Field Effects

Cross sections measured by ion mobility spectrometry are corrected for collision frequency and cooling/heating-controlled momentum transfer.

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Characterisation of Calmodulin Structural Transitions by Ion Mobility Mass Spectrometry

Australian Journal of Chemistry ◽

10.1071/ch12047 ◽

2012 ◽

Vol 65 (5) ◽

pp. 504 ◽

Cited By ~ 5

Author(s):

Antonio N. Calabrese ◽

Lauren A. Speechley ◽

Tara L. Pukala

Keyword(s):

Mass Spectrometry ◽

Cross Section ◽

Cross Sections ◽

Ion Mobility ◽

Collision Cross Section ◽

Travelling Wave ◽

Ion Mobility Mass Spectrometry ◽

Structural Transitions ◽

Calmodulin Binding ◽

Negative Mode

This study demonstrates the ability of travelling wave ion mobility-mass spectrometry to measure collision cross-sections of ions in the negative mode, using a calibration based approach. Here, negative mode ion mobility-mass spectrometry was utilised to understand structural transitions of calmodulin upon Ca2+ binding and complexation with model peptides melittin and the plasma membrane Ca2+ pump C20W peptide. Coexisting calmodulin conformers were distinguished on the basis of their mass and cross-section, and identified as relatively folded and unfolded populations, with good agreement in collision cross-section to known calmodulin geometries. Titration of calcium tartrate to physiologically relevant Ca2+ levels provided evidence for intermediately metalated species during the transition from apo- to holo-calmodulin, with collision cross-section measurements indicating that higher Ca2+ occupancy is correlated with more compact structures. The binding of two representative peptides which exemplify canonical compact (melittin) and extended (C20W) peptide-calmodulin binding models has also been interrogated by ion mobility mass spectrometry. Peptide binding to calmodulin involves intermediates with metalation states from 1–4 Ca2+, which demonstrate relatively collapsed structures, suggesting neither the existence of holo-calmodulin or a pre-folded calmodulin conformation is a prerequisite for binding target peptides or proteins. The biological importance of the different metal unsaturated calmodulin complexes, if any, is yet to be understood.

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Ion Mobility Spectrometry for Monitoring Chemical Warfare Agents

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.241-244.980 ◽

2012 ◽

Vol 241-244 ◽

pp. 980-983 ◽

Cited By ~ 2

Author(s):

Jian Zheng ◽

Tian Min Shu ◽

Jie Jin

Keyword(s):

Ion Mobility Spectrometry ◽

Ion Mobility ◽

Cluster Formation ◽

Chemical Warfare Agents ◽

Chemical Warfare ◽

Ambient Conditions ◽

Ionization Source ◽

Warfare Agents ◽

Positive Mode ◽

Detecting Method

The technique of ion mobility spectrometry (IMS) offers a practical and fast detecting method in ambient conditions to estimate whether there may presence contrabands or even chemical warfare agents (CWAs). In this work we have investigated a self-made radioactive 63Ni (β emission) ionization source for ion mobility spectrometry employed with an atmospheric pressure to detect real CWAs, such as GB, GD, HD, VX from aerosol samples. Furthermore, we have experimentally studied the influence of drift tube temperature not only in ion cluster formation in the positive mode, but also the detection limitation of CWAs.

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