33 research outputs found
MALDI Imaging and Structural Analysis of Rat Brain Lipid Negative Ions with 9-Aminoacridine Matrix
Mass spectrometry imaging is of growing interest for
chemical mapping of lipids at the surface of tissue sections. Many
efforts have been devoted to optimize matrix choice and deposition
technique for positive ion mode analyses. The identification of lipid
species desorbed from tissue sections in the negative mode can be
significantly improved by using 9-aminoacridine together with a robust
deposition method, yielding a superior signal-to-noise ratio and thus
a better contrast for the ion images in comparison to classical matrices
such as α-cyano-4-hydroxycinnamic acid, 2,5-dihydroxybenzoic
acid, or 2,4,6-trihydroxyacetophenone. Twenty-eight different lipid
species (phosphatidic acids, phosphatidylethanolamines, phosphatidylserines,
phosphatidylglycerols, phosphatidylinositols, phosphatidylinositol-phosphates,
and sulfatides) were scrutinized on rat brain tissue sections, and
systematic MS/MS studies were conducted. It was possible to identify
isobaric species differing by their fatty acid chains thanks to the
improved sensitivity
Insights into the MALDI Process after Matrix Deposition by Sublimation Using 3D ToF-SIMS Imaging
Imaging
mass spectrometry (IMS) has become a powerful tool to characterize
the spatial distribution of biomolecules in thin tissue sections.
In the case of matrix-assisted laser desorption ionization (MALDI)
IMS, homogeneous matrix deposition is critical to produce high-quality
ion images, and sublimation in particular has shown to be an excellent
matrix deposition method for the imaging of lipids. Matrix deposition
by sublimation is, however, a completely solvent-free system, which
ought to prevent the mixing of matrix and analytes thought to be necessary
for successful MALDI. Using 3D time-of-flight secondary ion imaging
mass spectrometry, we have studied the matrixâtissue interface
in 3D with high resolution to understand the MALDI process of lipids
after matrix deposition by sublimation. There is a strong indication
that diffusion is the process by which lipids migrate from the tissue
to the matrix layer. We show that triacylglycerols and phospholipids
have a delayed migratory trend as compared to diacylglycerols and
monoacylglycerols, which is dependent on time and matrix thickness.
Additional experiments show that a pure lipidâs capacity to
migrate into the matrix is dependent on its fluidity at room temperature.
Furthermore, it is shown that cholesterol can only migrate in the
presence of a (fluid) lipid and appears to fluidize lipids, which
could explain its colocalization with the diacylglycerols and monoacylglycerols
in the matrix
Identification of the Environmental Neurotoxins Annonaceous Acetogenins in an Annona cherimolia Mill. Alcoholic Beverage Using HPLC-ESI-LTQ-Orbitrap
Epidemiological
and toxicological studies have suggested Annonaceaeous
acetogenins to be environmental neurotoxins responsible for sporadic
atypical parkinsonism/dementia in tropical areas. These compounds
are present in the tropical genus <i>Annona</i> (Annonaceae),
known for its fruit-yielding cultivated species such as Annona cherimolia. This species is widely cultivated
in South America, Spain, and Portugal and yields acetogenins in its
seeds, stems, and roots. The presence of these compounds in the pulp
of its fruit and in derived food products is unclear. An innovative
and sensitive methodology by HPLC-ESI-LTQ-Orbitrap with postcolumn
infusion of lithium iodide was used to identify the presence of low
levels of acetogenins in an <i>A. cherimolia</i> Mill. fruit-based
commercial alcoholic beverage. More than 80 representatives were detected,
and the 31 most intense acetogenins were identified. All together
these findings indicate that this species should be considered as
a risk factor within the framework of a worldwide problem of food
toxicity
Argon Cluster Ion Source Evaluation on Lipid Standards and Rat Brain Tissue Samples
Argon cluster ion sources for sputtering
and secondary ion mass spectrometry use projectiles consisting of
several hundreds of atoms, accelerated to 10â20 keV, and deposit
their kinetic energy within the top few nanometers of the surface.
For organic materials, the sputtering yield is high removing material
to similar depth. Consequently, the exposed new surface is relatively
damage free. It has thus been demonstrated on model samples that it
is now really possible to perform dual beam depth profiling experiments
in organic materials with this new kind of ion source. Here, this
possibility has been tested directly on tissue samples, 14 ÎŒm
thick rat brain sections, allowing primary ion doses much larger than
the so-called static secondary ion mass spectrometry (SIMS) limit
and demonstrating the possibility to enhance the sensitivity of time-of-flight
(TOF)-SIMS biological imaging. However, the depth analyses have also
shown some variations of the chemical composition as a function of
depth, particularly for cholesterol, as well as some possible matrix
effects due to the presence or absence of this compound
Spectroscopic analysis of non-steatotic hepatocytes on fatty liver.
<p>Spectroscopic analyses were performed on periportal hepatocytes on tissue section from normal or fatty liver. The video image is shown (left panel) with the corresponding averaged IR spectra (right panel) and the chemical imaging of the sum of DAG (middle panel).</p
Assignment of frequency to chemical functions.
<p>From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0007408#pone.0007408-Dreissig1" target="_blank">[19]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0007408#pone.0007408-Banyay1" target="_blank">[20]</a>.</p
Histological features of steatosis.
<p>Tissue sections of 6 ”m thickness were performed on paraffin embedded biopsies from normal liver or from fatty liver and stained with HES (hematoxylin, eosin and safran). Normal hepatic lobule without steatosis (left panel) or fatty liver area exhibiting macrovacuolar and microvesicular steatosis (right panel) are shown. Upper panel: Ă100, lower panel: Ă400. PT: portal tract, BD: biliary duct, PV: portal vein, HA: hepatic artery, CLV: centrilobular vein, SV: steatotic vacuole.</p
Second derivatives of IR spectra.
<p>Spectra recorded on steatosis or non-steatotic hepatocytes were superimposed (upper panel). Second derivatives of the spectra were calculated and superimposed in the frequency domain 2600â3200 cm<sup>â1</sup> (lower panel).</p
Analysis of steatosis using synchrotron FTIR microspectroscopy.
<p>A) Optical image of steatotic hepatocytes containing steatotic vesicles (white star) and non-steatotic hepatocytes (black star). B) Averaged IR spectra recorded inside steatotic vesicles (upper spectrum in blue) or on non-steatotic hepatocytes (lower spectrum in red). The band corresponding to olefin (3000â3060 cm<sup>â1</sup>) is labelled by a black arrow. C) Chemical imaging of some bands on the tissue section.</p