Browsing by Subject "Ion mobility"

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    Dueling Electrospray Implemented on a Traveling-Wave Ion Mobility/Time-Of-Flight Mass Spectrometer: Towards a Gas-Phase Workbench for Structural Biology
    (Elsevier, 2019-07-05) Webb, Ian; Morrison, Lindsay; Brown, Jeff
    The traveling wave trap cell of a commercial ion mobility mass spectrometer (IM/MS) was used as a gas-phase reactor for covalent chemistry by making a simple modification to a standard nanoelectrospray source. Reagents and analytes were generated from pulsed opposite polarity nanoelectrospray sources and isolated by their m/z prior to reaction. Covalent bond formation was first observed with the model peptide angiotensin I. The modification site was identified as the N-terminus of the peptide by collision induced dissociation (CID). The IM cell separated the covalent reaction product from the proton transfer product by their respective ion mobilities. Next, the effects of several trapping parameters, including the trap traveling wave height, the trap RF voltage, and the trap pressure, were evaluated. Decreasing traveling wave height and increasing RF voltage and pressure increased the number of proton transfer events from apomyoglobin to reagent anions. The 6+ charge state of ubiquitin generated from nanospray under native-like conditions was covalently modified in the gas phase through ion/ion reactions. Probing the reacted protein with CID led to the assignment of lysine 29 and arginine 54 as reactive nucleophiles accessible to the reagent. IM analysis of the unmodified native-like 6+ charge state revealed that the gas-phase structure of the protein in the trap was in its compact form. Overall, we introduce a promising method for three-dimensional structural characterization of biomacromolecules.
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    Modeling and experimenting a novel inverted drift tube device for improved mobility analysis of aerosol particles
    (2017-12) Nahin, Md Minal; Larriba-Andaluz, Carlos
    Ion Mobility Spectrometry (IMS) is an analytical technique for separation of charged particles in the gas phase. The history of IMS is not very old, and in this century, the IMS technique has grown rapidly in the advent of modern instruments. Among currently available ion mobility spectrometers, the DTIMS, FAIMS, TWIMS, DMA are notable. Though all the IMS systems have some uniqueness in case of particle separation and detection, however, all instruments have common shortcomings. They lack in resolution, which is independent of mobility of different charged particles and they are not able to separate bigger particles (20 120 nm) with good accuracy. The work presented here demonstrates a new concept of IMS technique at atmospheric pressure which has a resolution much higher than that of the currently available DTIMS (Drift Tube Ion Mobility Spectrometry) instruments. The unique feature of this instrument is the diffusion auto-correction. Being tunable, It can separate the wide range of particles of different diameters. The working principle of this new IMS technique is different from the typical DTIMS and to simply put, it can be considered as an inversion of commonly used technique, so termed as Inverted Drift Tube (IDT).The whole work performed here can be divided into three major phases. In the first phase, the analytical solution was derived for two new separation techniques: IPF (Intermittent push flow) and NSP (Nearly stopping potential) separations. In the next phase, simulations were done to show the accuracy of the analytical solution. An ion optics simulator software called SIMION 8.1 was used for conducting the simulation works. These simulations adopted the statistical diffusion (SDS) collision algorithm to emulate the real scenario in gas phase more precisely. In the last phase, a prototype of experimental setup was built. The experimental results were then validated by simulated results.
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    A perspective on the theoretical and numerical aspects of Ion Mobility Spectrometry
    (Elsevier, 2021-12) Larriba-Andaluz, Carlos; Mechanical Engineering, School of Engineering and Technology
    Ion Mobility Spectrometry (IMS) has become a ubiquitous analytical technique, in particular when used as an orthogonal technique to Mass Spectrometry (MS). As separations of ions in the gas phase become more precise, the need to provide a suitable theory that explains the observed differences is apparent. While the theory exists, much of it is obscured due to the difficulty of the equations and the approximations to the solution. This work explores some of the more useful theoretical approaches to IMS while making use of a full Monte Carlo simulations algorithm to provide some pedagogical examples that characterize the reasons behind the different theoretical approaches, and whether they need to be used for a particular calculation. To improve the existing theory, reliable empirical data is required. For such reason, an appropriate labeling system for mobility is proposed here requiring that at least the temperature, gas, electric field, and instrument employed are provided and which is an extension of the previous protocol.