Investigation of the Reactivity of the Cytosine-5-yl Radical Ion using Ion Trap Mass Spectrometry

Nucleobases play a significant biological role in DNA and RNA. Since the discovery that halogenated pyrimidines act as a good sensitizer for radiotherapy, the attention on 5-halouracil has increased, however the photoreactivity of cytosine and its derivatives has not been investigated. This study presents, for the first time, the highly selective generation of the cytosine-5-yl radical ion obtained by photodissociation of halogenated precursors. Using a modified linear ion trap mass spectrometer, gas-phase reactions and product channels are presented and mechanisms of possible pathways of photodissociation are discussed for reactions between the radical ion with molecular oxygen and unsaturated hydrocarbons including, propene, propyne and acetylene. Molecular oxygen reacting with the protonated cytosine-5-yl radical forms products at m/z 126 and 127, showing an efficiency of = 11.4 ± 0.9%. Reactions of propene and propyne present an efficiency of = 52.6 ± 0.8% and = 111 ± 0.1%, showing that unsaturated hydrocarbons reactions are highly efficient and significantly more efficient than molecular oxygen reactions

Mass Spectrometry Imaging of Lipids using MALDI Coupled with Plasma-Based Post-Ionisation on a Trapped Ion Mobility Mass Spectrometer

Here we report the development and optimization of a mass spectrometry imaging (MSI) platform that combines atmospheric-pressure matrix-assisted laser desorption/ionization platform with plasma post-ionization (AP-MALDI-PPI) and trapped ion mobility spectrometry (TIMS). We discuss optimal parameters for operating the source, characterize the behaviour of a variety of lipid classes in positive- and negative-ion modes and explore the capabilities for lipid imaging using murine brain tissue. The instrument generates high signal-to-noise for numerous lipid species, with mass spectra sharing many similarities to those obtained using laser post-ionization (MALDI-2). The system is especially well suited for detecting lipids such as phosphatidylethanolamine (PE) as well as numerous sphingolipid classes and glycerolipids. For the first time, the coupling of plasma-based post-ionization with ion mobility is presented and we show the value of ion mobility for the resolution and and identification of species within rich spectra that contain numerous isobaric/isomeric signals that are not resolved in the m/z dimension alone, including isomeric PE and demethylated phosphatidylcholine lipids produced by in-source fragmentation. The reported instrument provides a powerful and user-friendly approach for MSI of lipids

Mass Spectrometry Imaging of Lipids Using MALDI Coupled with Plasma-Based Post-Ionization on a Trapped Ion Mobility Mass Spectrometer

Here we report the development and optimization of a mass spectrometry imaging (MSI) platform that combines an atmospheric-pressure matrix-assisted laser desorption/ionization platform with plasma postionization (AP-MALDI-PPI) and trapped ion mobility spectrometry (TIMS). We discuss optimal parameters for operating the source, characterize the behavior of a variety of lipid classes in positive- and negative-ion modes, and explore the capabilities for lipid imaging using murine brain tissue. The instrument generates high signal-to-noise for numerous lipid species, with mass spectra sharing many similarities to those obtained using laser postionization (MALDI-2). The system is especially well suited for detecting lipids such as phosphatidylethanolamine (PE), as well as numerous sphingolipid classes and glycerolipids. For the first time, the coupling of plasma-based postionization with ion mobility is presented, and we show the value of ion mobility for the resolution and identification of species within rich spectra that contain numerous isobaric/isomeric signals that are not resolved in the m/z dimension alone, including isomeric PE and demethylated phosphatidylcholine lipids produced by in-source fragmentation. The reported instrument provides a powerful and user-friendly approach for MSI of lipids

Mass Spectrometry Imaging of Lipids Using MALDI Coupled with Plasma-Based Post-Ionization on a Trapped Ion Mobility Mass Spectrometer

Here we report the development and optimization of a mass spectrometry imaging (MSI) platform that combines an atmospheric-pressure matrix-assisted laser desorption/ionization platform with plasma postionization (AP-MALDI-PPI) and trapped ion mobility spectrometry (TIMS). We discuss optimal parameters for operating the source, characterize the behavior of a variety of lipid classes in positive- and negative-ion modes, and explore the capabilities for lipid imaging using murine brain tissue. The instrument generates high signal-to-noise for numerous lipid species, with mass spectra sharing many similarities to those obtained using laser postionization (MALDI-2). The system is especially well suited for detecting lipids such as phosphatidylethanolamine (PE), as well as numerous sphingolipid classes and glycerolipids. For the first time, the coupling of plasma-based postionization with ion mobility is presented, and we show the value of ion mobility for the resolution and identification of species within rich spectra that contain numerous isobaric/isomeric signals that are not resolved in the m/z dimension alone, including isomeric PE and demethylated phosphatidylcholine lipids produced by in-source fragmentation. The reported instrument provides a powerful and user-friendly approach for MSI of lipids