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Cyclic oligosaccharides are well known to interact with various metals, able to form supramolecular complexes with distinct sizes and shapes. However, the presence of various isomers in a sample, including positional isomers and conformers, can significantly impact molecular recognition, encapsulation ability and chemical reactivity. Therefore, it is crucial to have tools for deep samples probing and correlation establishments. The emerging ion mobility mass spectrometry (IM-MS) has the advantages to be rapid and sensitive, but is still in its infancy for the investigation of supramolecular assemblies. In the herein study, it was demonstrated that IM-MS is suitable to discriminate several isomers of cyclodextrins (CD)-metals complexes, used as cyclic oligosaccharide models. In this sense, we investigated branched 6-O-α-glucosyl- or 6-O-α-maltosyl-β-cyclodextrins (G 1 -β-CD and G 2 -β-CD) and their purely cyclic isomers: CD8 (γ-CD) and CD9 (δ-CD). The corresponding collision cross section (CCS) values were deducted for the main positive singly and doubly charged species. Experimental CCS values were matched with models obtained from molecular modelling. The high mobility resolving power and resolution enabled discrimination of positional isomers, identification of various conformers and accurate relative content estimation. These results represent a milestone in the identification of carbohydrate conformers that cannot be easily reached by other approaches. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Structural analysis of C 5 H 7 + using ion-mobility spectrometry. • Structures of C 5 H 7 + derived from the precursors MPD and cyclohexene were identical. • Dissociation pathway DFT calculation of MPD to cyclopentenium cations. The formation pathways, intermediates , and products of alkadienes dissociation reactions are fundamental to combustion chemistry, yet their understanding is limited. Herein, the C 5 H 7 + fragment ion derived from 3-methyl-1,4-pentadiene (MPD) was investigated using an ion mobility/mass spectrometer. The reduced mobilities (K 0) of the C 5 H 7 + fragment ions generated by MPD and cyclohexene (used to generate the fragment ion standard) correlated with effective temperature in He buffer gas, and showed that these fragments were identical cyclopentenium cations. The dissociation of MPD to cyclopentenium cations was investigated using density functional theory calculations, which revealed the feasibility of this dissociation pathway over other fragments. [ABSTRACT FROM AUTHOR]

In this study, the size and shape of supramolecular assemblies between cyclo-oligosaccharides and proton, ammonium or a series of alkali metals by electrospray coupled to trapped ion mobility-mass spectrometry (ESI-TIMS) have investigated. Native cyclodextrins (CD) were selected as models, and collision cross section (CCS) values were deducted for the main positive singly and doubly charged species. Experimental CCS values were in good agreement with those obtained from molecular modeling. Due to the high mobility resolving power and resolution, it was possible to highlight the presence of various conformers. Also, TIMS allowed to discriminate and estimate the content of various orientations from non-covalent nanotubes-based CD, involving secondary/secondary rim hydroxyl groups (head-to head), primary/secondary rim (head-to-tail) hydroxyl groups or primary/primary rim (tail-to-tail) hydroxyl groups interactions. Such results pave the way for a better knowledge of the topology of cyclo-oligosaccharides based supramolecular complexes, demonstrating that TIMS can be a particularly attractive molecular descriptor. [Display omitted] [ABSTRACT FROM AUTHOR]

Amylin amyloid deposition is a common feature in the pancreas of type-2 diabetic (T2D) patients, and may play a role in islet beta-cell death and disease development. Type-2 diabetes is also characterised by a dysregulation of systemic copper. While the relationship between these features is unclear, previous work has shown that copper can form a complex with amylin, which in turn prevents amylin misfolding, oligomerisation and fibril formation, and that this in turn decreases amylin-mediated cytotoxicity. To date, the nature of this interaction has not been determined. In this study, we have used ion mobility mass spectrometry to probe the effects of copper on amylin oligomer formation and to define the binding site(s) of copper on the amylin peptide. Here we show that there are two distinct sites to which copper can bind. The first is at a location in the C-terminal 5 amino acids of the peptide. The second is on Ala25, a residue which is known to be critical for the misfolding ability of human amylin. This interaction is not observed under standard mass spectrometry (acidic) conditions but is present at physiological pH values. These data further characterise the amylin–copper interaction, and may suggest a potential trigger for amylin misfolding in T2D. [ABSTRACT FROM AUTHOR]

Abstract: The substrate-free hydrolysis of Zn nanocrystals was investigated as the second step in a ZnO/Zn solar water-splitting thermochemical cycle. In this work, we combined two different ion-mobility schemes in series to study the hydrolysis kinetics of size-selected zinc nanocrystals (NCs). The first mobility characterization size selects particles with a differential mobility analyzer (DMA). The second mobility characterization employs an aerosol particle mass analyzer (APM) and measures changes in mass resulting from a controlled hydrolysis of the Zn NCs. A low temperature reaction mechanism is proposed to explain the mass change behavior of Zn NCs hydrolysis at 100–250°C. An Arrhenius law was used to extract the reaction kinetic parameters. The hydrolysis activation energy and the order of the reaction with respect to water mole fraction were found to be 24±2kJ/mol and 0.9±0.1, respectively. Complete conversion of 70nm Zn NCs was achieved at 175°C with a residence time of about 10s and water vapor mole fraction of 19%. [Copyright &y& Elsevier]

Abstract: The ion–neutral interaction potentials of HeO+ and HeO− are calculated from experimental gaseous ion-mobility data by using the direct inversion method. The obtained potentials are in good agreement with recent ab initio potentials, and they were used to obtain best parameters for the Morse–Spline–Van der Waals (MSV) potential model. The MSV potentials were then employed to compute the mobilities of O+ and O− ions in helium gas. Results show that the MSV model potentials reproduce the experimental ion mobilities within their experimental accuracy. [Copyright &y& Elsevier]

Abstract: We report ion-mobility measurements with a modified triple quadrupole mass spectrometer fitted with an ion molecule reactor (IMR) designed to investigate ion molecule reactivity in organic mass spectrometry. Functionalized pentacene ions, which are generally unreactive were chosen for study to decouple drift/diffusion effects from reactivity (including clustering). The IMR is equipped with a variable axial electrostatic drift field (ADF) and is able to trap ions. These capabilities were successfully employed in the measurement of ion mobilities in different modes of IMR operation. Theoretical modeling of the drift dynamics and the special localization of the large ion packet was successfully implemented. The contribution of the quadrupole RF field to the drift dynamics also was taken into consideration. [Copyright &y& Elsevier]