Internal Energy Deposition in Infrared Matrix-Assisted Laser Desorption Electrospray Ionization With and Without the Use of Ice as a Matrix

Tu, Anqi; Muddiman, David C.

doi:10.1007/s13361-019-02323-2

Cited by 32 publications

(45 citation statements)

References 57 publications

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“…Tu and Muddiman [70] recently reported that infrared matrix-assisted laser desorption/ionisation (IR-MALDESI) was suitable for intact protein complex analysis. The technique uses an infrared laser to desorb material, rather than a solvent spray, with electrospray post-ionisation.…”

Section: Desorption Techniquesmentioning

confidence: 99%

In situ mass spectrometry analysis of intact proteins and protein complexes from biological substrates

Hale

Cooper

2020

Biochemical Society Transactions

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Advances in sample preparation, ion sources and mass spectrometer technology have enabled the detection and characterisation of intact proteins. The challenges associated include an appropriately soft ionisation event, efficient transmission and detection of the often delicate macromolecules. Ambient ion sources, in particular, offer a wealth of strategies for analysis of proteins from solution environments, and directly from biological substrates. The last two decades have seen rapid development in this area. Innovations include liquid extraction surface analysis, desorption electrospray ionisation and nanospray desorption electrospray ionisation. Similarly, developments in native mass spectrometry allow protein–protein and protein–ligand complexes to be ionised and analysed. Identification and characterisation of these large ions involves a suite of hyphenated mass spectrometry techniques, often including the coupling of ion mobility spectrometry and fragmentation techniques. The latter include collision, electron and photon-induced methods, each with their own characteristics and benefits for intact protein identification. In this review, recent developments for in situ protein analysis are explored, with a focus on ion sources and tandem mass spectrometry techniques used for identification.

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Section: Desorption Techniquesmentioning

confidence: 99%

In situ mass spectrometry analysis of intact proteins and protein complexes from biological substrates

Hale

Cooper

2020

Biochemical Society Transactions

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“…In this study, we aimed at in situ analysis of FA positional isomers in animal tissues by coupling the on‐tissue mCPBA epoxidation derivatization with an ambient mass spectrometry imaging (MSI) technique termed infrared matrix‐assisted laser desorption electrospray ionization (IR‐MALDESI). IR‐MALDESI is a hybrid and soft 26,27 ionization source based on IR‐laser desorption followed by electrospray post‐ionization, 28–30 requiring little to no sample preparation prior to analysis. The analytical performance of the epoxidation method was first evaluated with representative FA standards, and the practical utility to biological tissue analysis was further demonstrated on rat liver and human bladder cancer tissue.…”

Section: Introductionmentioning

confidence: 99%

In situ detection of fatty acid C=C positional isomers by coupling on‐tissue mCPBA epoxidation with infrared matrix‐assisted laser desorption electrospray ionization mass spectrometry

Garrard

Said

et al. 2021

Rapid Comm Mass Spectrometry

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Rationale Unsaturated fatty acids (UFAs) play vital roles in regulating cellular functions. In‐depth structural characterization of UFAs such as localizing carbon–carbon double bonds is fundamentally important but poses considerable challenges in mass spectrometry (MS) given that the most widely accessible ion activation method, low‐energy collision‐induced dissociation (CID), primarily generates uninformative fragments (e.g., neutral loss of CO2) that are not suggestive of the double‐bond positions. Methods m‐Chloroperoxybenzoic acid (mCPBA) was uniformly deposited onto the sample slides using a TM Sprayer, converting the carbon–carbon double bonds into epoxides under ambient conditions. The epoxidation product was ionized in situ by infrared matrix‐assisted laser desorption electrospray ionization mass spectrometry (IR‐MALDESI‐MS), and subsequently cleaved via CID, generating a diagnostic ion pair associated with the double‐bond position. The reaction efficiency, sensitivity and relative quantification capability of the method were validated with five UFA standards dried on glass slides, and then this strategy was demonstrated on thin tissue sections of rat liver and human bladder. Results The mCPBA reaction yielded conversion rates in the range of 44–60% in 10 min with high specificity and sensitivity. Further tandem mass spectrometry (MS/MS) of the mono‐epoxidized products generated informative fragment ions specific to the double‐bond positions, and relative quantification of positional isomers in binary mixtures was performed across a wide mole fraction from 0 to 1. An innovative spiral scan pattern was utilized during data acquisition, elucidating the major isomeric compositions of multiple UFAs from a tissue section in a single run. Conclusions The on‐tissue mCPBA epoxidation was implemented into an ambient MS imaging workflow to offer a rapid and simple way for in situ identification and relative quantification of double‐bond positional isomers without the requirement for instrument modification. The method can be readily implemented on many other MS platforms to reveal the role of double‐bond positional isomers in lipid biology and to discover potential biomarkers.

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“…33,34 Several studies have focused on the formation of carotenoid (and other hydrocarbon) radical cations specifically in ESI, which could offer some explanation for how radical cationization could occur for MALDESI. [35][36][37] In ESI, radical cationization is often facilitated by electrochemical oxidation at the solvent/electrospray needle interface, [38][39][40] which can be improved by adding solution-phase oxidants. 41,42 However, after studying both mechanisms, questions remained, because β-carotene did not flow through the solvent/ electrospray emitter interface, nor were any strong solution-phase oxidants present in the electrospray solution during MALDESI experiments.…”

Section: Introductionmentioning

confidence: 99%

Investigations of β‐carotene radical cation formation in infrared matrix‐assisted laser desorption electrospray ionization (IR‐MALDESI)

Bagley

Muddiman

2021

Rapid Comm Mass Spectrometry

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Radical cationization of endogenous hydrocarbons in cherry tomatoes was previously reported using infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI), a mass spectrometry imaging technique that operates at ambient conditions and requires no sample derivatization. Due to the surprising nature of this odd-electron ionization, subsequent experiments were performed on β-carotene to determine the amount of radical cationization across different sampling conditions.Methods: β-Carotene was analyzed across a variety of sample states using IR-MALDESI followed by Orbitrap mass spectrometric analysis: first, as a standard in ethanol in a well plate; second, as particulates on printer paper; and third, as particulates covered by an ice matrix. These techniques were also performed with a β-carotene standard either in solution with a reducing agent (ascorbic acid) or with ascorbic acid in the electrospray solution.Results: Tandem mass spectrometry confirmed the presence of the radical cation of β-carotene by comparing fragments against NIST and METLIN databases. It was always analyzed as a radical cation when sampled from solution, where ascorbic acid increased radical cation abundance when in solution with β-carotene. Mixed-mode ionization between radical cationization and proton adduction was observed from dried particulates using IR-MALDESI.Conclusions: There are several potential mechanisms for β-carotene radical cationization prior to IR-MALDESI analysis, with multiphoton ionization, thermal degradation, and/or reaction with oxygen appearing to be the most logical explanations. Furthermore, although not the primary cause, changing certain aspects of sample conditions can result in significant mixed-mode ionization with competing protonation.

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Internal Energy Deposition in Infrared Matrix-Assisted Laser Desorption Electrospray Ionization With and Without the Use of Ice as a Matrix

Cited by 32 publications

References 57 publications

In situ mass spectrometry analysis of intact proteins and protein complexes from biological substrates

In situ mass spectrometry analysis of intact proteins and protein complexes from biological substrates

In situ detection of fatty acid C=C positional isomers by coupling on‐tissue mCPBA epoxidation with infrared matrix‐assisted laser desorption electrospray ionization mass spectrometry

Investigations of β‐carotene radical cation formation in infrared matrix‐assisted laser desorption electrospray ionization (IR‐MALDESI)

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