2 research outputs found
Characterization of Phosphatidylcholine Oxidation Products by MALDI MS<sup><i>n</i></sup>
Phospholipid oxidation has been implicated
in the pathogenesis
and progression of numerous age-related and neurodegenerative diseases.
Despite these implications, this broad class of biomolecules remains
poorly characterized. In this work, the fragmentation patterns of
[M + H]<sup>+</sup> and [M + Na]<sup>+</sup> ions of intact phosphatidylcholine
oxidation products (OxPCs) were characterized by matrix-assisted laser
desorption/ionization tandem mass spectrometry (MALDI MS<sup><i>n</i></sup>, <i>n</i> = 2, 3, and 4). MS<sup>2</sup> of both the [M + H]<sup>+</sup> and [M + Na]<sup>+</sup> ions of
short-chain OxPCs yielded product ions related to the PC headgroup
and the fatty acid substituents. MS<sup>3</sup> of the [M + Na ā
NĀ(CH<sub>3</sub>)<sub>3</sub>]<sup>+</sup> ions yielded fragmentation
indicative of the OxPC modification; specifically, a product ion corresponding
to the neutral loss of CO<sub>2</sub> (NL of 44) was observed for
OxPCs containing a terminal carboxylic acid rather than an aldehyde.
Furthermore, MS<sup>4</sup> of the [M + Na ā HPO<sub>4</sub>(CH<sub>2</sub>)<sub>2</sub>NĀ(CH<sub>3</sub>)<sub>3</sub>]<sup>+</sup> ions resulted in fragmentation pathways dependent on the <i>sn</i>-2 fatty acid chain length and type of functional group(s).
Specifically, CHO-containing OxPCs with palmitic acid esterified to
the <i>sn</i>-1 position of the glycerol backbone yielded
a NL of 254, 2 u less than the nominal mass of palmitic acid, whereas
the analogous terminal COOH-containing OxPCs demonstrated a NL of
256. Finally, the presence of a Ī³-ketone relative to the terminal
carboxyl group resulted in CāC bond cleavages along the <i>sn</i>-2 substituent, providing diagnostic product ions for
keto-containing OxPCs. This work illustrates the enhanced selectivity
afforded by MS<sup><i>n</i></sup> on the linear ion trap
and develops a method for the identification of individual products
of PC oxidation
MALDI Mass Spectrometry Imaging in Microscope Mode with Infrared Lasers: Bypassing the Diffraction Limits
This letter demonstrates
the use of infrared matrix-assisted laser
desorption/ionization coupled with microscope mode mass spectrometry
imaging. It is aimed to explore the use of intrinsic water in tissue
as a matrix for imaging at spatial resolutions below the diffraction
limit of the employed IR optics. Stigmatic ion optics with a magnification
factor of ā¼70 were used to project the spatial distribution
of produced ions onto a detector while separating ions with different
mass-to-charge ratios using a time-of-flight mass spectrometer. A
pixelated detector was used to simultaneously record arrival time
and impact position. A previously described dried-droplet sample system
of 2,5-dihydroxybenzoic acid (DHB) and 5 peptides covered by a copper
grid for defined surface structure was used to benchmark the light-
and ion-optical setup for spatial resolution and mass spectrometric
performance. A spatial resolving power of 9.8 Ī¼m, well below
the optical limit of diffraction (14 Ī¼m for the given setup),
was established. After, frozen cryo-sections from a biological model
system were measured by exploiting the endogenous water content as
a matrix. Principal component analysis enabled a clear distinction
between distinct tissue regions identified by both light microscopy
and MS imaging