High-quality matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) of lipids in biological tissue relies on the fabrication of a homogeneous matrix coating featuring best possible analyte integration. This communication addresses a matrix vapor deposition/recrystallization process for the application of 1,5-diaminonaphthalene (1,5-DAN) onto slices of human aortic tissue. The matrix coating is compatible with both positive- as well as negative-ion-mode MALDI MSI facilitating a significantly enhanced detection of lipid-related signals in different cell layers of blood vessel walls.
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Desorption electrospray ionization
(DESI), easy ambient sonic-spray
ionization (EASI) and low-temperature plasma (LTP) ionization are
powerful ambient ionization techniques for mass spectrometry. However,
every single method has its limitation in terms of polarity and molecular
weight of analyte molecules. After the miniaturization of every possible
component of the different ion sources, we finally were able to embed
two emitters and an ion transfer tubing into a small, hand-held device.
The pen-like interface is connected to the mass spectrometer and a
separate control unit via a bundle of flexible tubing and cables.
The novel device allows the user to ionize an extended range of chemicals
by simple switching between DESI, voltage-free EASI, or LTP ionization
as well as to freely move the interface over a surface of interest.
A mini camera, which is mounted on the tip of the pen, magnifies the
desorption area and enables a simple positioning of the pen. The interface
was successfully tested using different types of chemicals, pharmaceuticals,
and real life samples. Moreover, the combination of optical data from
the camera module and chemical data obtained by mass analysis facilitates
a novel type of imaging mass spectrometry, which we name “interactive
mass spectrometry imaging (IMSI)”.
We
report our studies on the development of a catalytic cycloisomerization
of 2,2-disubstituted neopentylic epoxides to produce highly substituted
tetralins and chromanes. Termination of the sequence occurs via Friedel–Crafts-type
alkylation of the remote (hetero)arene linker. The transformation
is efficiently promoted by sulfuric acid and proceeds best in 1,1,1,3,3,3-hexafluoroisopropanol
(HFIP) as the solvent. Variation of the substitution pattern provided
detailed insights into the migration tendencies and revealed a competing
disproportionation pathway of dihydronaphthalenes.
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