Production and analysis of multiply charged negative ions by liquid atmospheric pressure matrix‐assisted laser desorption/ionization mass spectrometry

Hale, Oliver J.; Ryumin, Pavel; Brown, Jeffery M.; Morris, Michael; Cramer, Rainer

doi:10.1002/rcm.8246

Cited by 10 publications

(12 citation statements)

References 27 publications

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“…Laser desorption MS and MALDI-MS ion sources operated under vacuum conditions until around 2000 when Laiko et al demonstrated the first AP-MALDI-MS ion source, coupled to an orthogonal time-of-flight (ToF) instrument [3]. Recently, exciting data showing generation of multiply charged species has been demonstrated in ion sources of this form [4,5]. The current state of the art with regards to AP-MALDI-MSI is the high resolution ion source developed by the Spengler group [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Construction and testing of an atmospheric-pressure transmission-mode matrix assisted laser desorption ionisation mass spectrometry imaging ion source with plasma ionisation enhancement

Steven

Shaw

Murta

et al. 2019

Analytica Chimica Acta

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Matrix assisted laser desorption ionisation mass spectrometry (MALDI-MS) at atmospheric pressure (AP) is, with a few notable exceptions, overshadowed by its vacuum based forms and AP transmission mode (TM) MALDI-MS lacks the uptake its potential benefits might suggest. The reasons for this are not fully understood and it is clear further development is required to realise the flexibility and power of this ionisation method and geometry. Here we report the build of a new AP-TM-MALDI-MSI ion source with plasma ionisation enhancement. This novel ion source is used to analyse a selection of increasingly complex systems from molecular standards to murine brain tissue sections. Significant enhancement of detected ion intensity is observed in both positive and negative ion mode in all systems, with up to 2000 fold increases observed for a range of tissue endogenous species. The substantial improvements conferred by the plasma enhancement are then employed to demonstrate the acquisition of proof of concept tissue images, with high quality spectra obtained down to 10 × 10 µm pixel size.

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Section: Introductionmentioning

confidence: 99%

Construction and testing of an atmospheric-pressure transmission-mode matrix assisted laser desorption ionisation mass spectrometry imaging ion source with plasma ionisation enhancement

Steven

Shaw

Murta

et al. 2019

Analytica Chimica Acta

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“…The neutral liquid MALDI matrix (neutral matrix) consisted of ethylene glycol dissolved in an aqueous ammonium acetate solution (200 mM) in a ratio of 3:5 (v/v), resulting in a pH value of approximately 7. The acidic liquid MALDI matrix (acidic matrix) was DHB dissolved at a concentration of 25 mg/mL in water/acetonitrile/ethylene glycol (3:7:6; v/v/v) with a pH value of approximately 2, which has previously been demonstrated to produce highly protonated protein ions. , Sodium iodide solution was used as provided for calibration of the TOF analyzer in the m / z range of 100–8000 by AP-LDI. A volume of 500 nL of the sodium iodide solution was spotted with 500 nL of ethylene glycol/water (3:5; v/v) and analyzed by ablating material from the droplet edge.…”

Section: Methodsmentioning

confidence: 99%

“…However, multiply charged ions may be produced using an AP ion source and liquid samples . In the case of ultraviolet (UV)-MALDI, the use of typically acidic liquid support matrices (LSMs) produces highly charged ions in the positive ion mode, while basic LSMs are beneficial for producing highly charged ions in the negative ion mode . Proteins as large as apo-transferrin (approximately 80 kDa) have been analyzed in this way .…”

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confidence: 99%

Atmospheric Pressure Ultraviolet Laser Desorption and Ionization from Liquid Samples for Native Mass Spectrometry

Hale

Cramer

2019

Anal. Chem.

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Understanding protein structure is vital for evaluating protein interactions with drugs, proteins, and other ligands. Native mass spectrometry (MS) is proving to be invaluable for this purpose, enabling analysis of “native-like” samples that mimic physiological conditions. Native MS is usually performed by electrospray ionization (ESI) with its soft ionization processes and the generation of multiply charged ions proving favorable for conformation retention and high mass analysis, respectively. There is scope to expand the currently available toolset, specifically to other soft ionization techniques such as soft laser desorption, for applications in areas like high-throughput screening and MS imaging. In this Letter, observations made from native MS experiments using an ultraviolet (UV) laser-based ion source operating at atmospheric pressure are described. The ion source is capable of producing predominately multiply charged ions similar to ESI. Proteins and protein complexes were analyzed from a native-like sample droplet to investigate the technique. Ion mobility-mass spectrometry (IM-MS) measurements showed that folded protein conformations were detected for ions with low charge states. This observation indicates the source is suitable for native MS analysis and should be further developed for higher mass analysis in the future.

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“…Cramer et al (University of Reading, Reading, UK) showed that, with a retrofitted heated inlet tube on a SYNAPT mass spectrometer (Waters, Wilmslow, UK), negatively multiply charged ions using a liquid matrix can be detected applying several kV difference between the plate and the heated inlet. 83 In collaborative work, Valentine and Li (West Virginia University, Institute, WV, USA) developed a vibrating sharp-edge spray, a voltage-free means of producing liquid droplets just outside a heated inlet tube. 84 Eberlin et al (University of Texas at Austin, Austin, TX, USA) uses a 'MasSpec Pen' for surface analysis using a type of liquid junction in combination with SAI to detect cancerous tissue during surgery.…”

Section: Introductionmentioning

confidence: 99%

An overview of biological applications and fundamentals of newinletandvacuumionization technologies

Trimpin

Marshall

Karki

et al. 2020

Rapid Comm Mass Spectrometry

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Rationale The developments of new ionization technologies based on processes previously unknown to mass spectrometry (MS) have gained significant momentum. Herein we address the importance of understanding these unique ionization processes, demonstrate the new capabilities currently unmet by other methods, and outline their considerable analytical potential. Methods The inlet and vacuum ionization methods of solvent‐assisted ionization (SAI), matrix‐assisted ionization (MAI), and laserspray ionization can be used with commercial and dedicated ion sources producing ions from atmospheric or vacuum conditions for analyses of a variety of materials including drugs, lipids, and proteins introduced from well plates, pipet tips and plate surfaces with and without a laser using solid or solvent matrices. Mass spectrometers from various vendors are employed. Results Results are presented highlighting strengths relative to ionization methods of electrospray ionization (ESI) and matrix‐assisted laser desorption/ionization. We demonstrate the utility of multi‐ionization platforms encompassing MAI, SAI, and ESI and enabling detection of what otherwise is missed, especially when directly analyzing mixtures. Unmatched robustness is achieved with dedicated vacuum MAI sources with mechanical introduction of the sample to the sub‐atmospheric pressure (vacuum MAI). Simplicity and use of a wide array of matrices are attained using a conduit (inlet ionization), preferably heated, with sample introduction from atmospheric pressure. Tissue, whole blood, urine (including mouse, chicken, and human origin), bacteria strains and chemical on‐probe reactions are analyzed directly and, especially in the case of vacuum ionization, without concern of carryover or instrument contamination. Conclusions Examples are provided highlighting the exceptional analytical capabilities associated with the novel ionization processes in MS that reduce operational complexity while increasing speed and robustness, achieving mass spectra with low background for improved sensitivity, suggesting the potential of this simple ionization technology to drive MS into areas currently underserved, such as clinical and medical applications.

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Production and analysis of multiply charged negative ions by liquid atmospheric pressure matrix‐assisted laser desorption/ionization mass spectrometry

Abstract: Negative ion mode is a sensitive alternative to positive ion mode in liquid AP-MALDI MS analysis. In particular, the analysis of lipids and DNA benefited from the complementarity of the detected lipid species and the vastly greater DNA ion signal intensities in negative ion mode.

Cited by 10 publications

References 27 publications

Construction and testing of an atmospheric-pressure transmission-mode matrix assisted laser desorption ionisation mass spectrometry imaging ion source with plasma ionisation enhancement

Construction and testing of an atmospheric-pressure transmission-mode matrix assisted laser desorption ionisation mass spectrometry imaging ion source with plasma ionisation enhancement

Atmospheric Pressure Ultraviolet Laser Desorption and Ionization from Liquid Samples for Native Mass Spectrometry

An overview of biological applications and fundamentals of newinletandvacuumionization technologies

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