2 research outputs found
Automated Platform for High-Resolution Tissue Imaging Using Nanospray Desorption Electrospray Ionization Mass Spectrometry
An automated platform has been developed for acquisition
and visualization of mass spectrometry imaging (MSI) data using nanospray
desorption electrospray ionization (nano-DESI). The new system enables
robust operation of the nano-DESI imaging source over many hours by
precisely controlling the distance between the sample and the nano-DESI
probe. This is achieved by mounting the sample holder onto an automated <i>XYZ</i> stage, defining the tilt of the sample plane, and recalculating
the vertical position of the stage at each point. This approach is
useful for imaging of relatively flat samples such as thin tissue
sections. Custom software called MSI QuickView was developed for visualization
of large data sets generated in imaging experiments. MSI QuickView
enables fast visualization of the imaging data during data acquisition
and detailed processing after the entire image is acquired. The performance
of the system is demonstrated by imaging rat brain tissue sections.
Low background noise enables simultaneous detection of lipids and
metabolites in the tissue section. High-resolution mass analysis combined
with tandem mass spectometry (MS/MS) experiments enabled identification
of the observed species. In addition, the high dynamic range (>2000)
of the technique allowed us to generate ion images of low-abundance
isobaric lipids. A high-spatial resolution image was acquired over
a small region of the tissue section revealing the distribution of
an abundant brain metabolite, creatine, on the boundary between the
white and gray matter. The observed distribution is consistent with
the literature data obtained using magnetic resonance spectroscopy
Formularity: Software for Automated Formula Assignment of Natural and Other Organic Matter from Ultrahigh-Resolution Mass Spectra
Ultrahigh
resolution mass spectrometry, such as Fourier transform
ion cyclotron resonance mass spectrometry (FT ICR MS), can resolve
thousands of molecular ions in complex organic matrices. A Compound
Identification Algorithm (CIA) was previously developed for automated
elemental formula assignment for natural organic matter (NOM). In
this work, we describe software Formularity with a user-friendly interface
for CIA function and newly developed search function Isotopic Pattern
Algorithm (IPA). While CIA assigns elemental formulas for compounds
containing C, H, O, N, S, and P, IPA is capable of assigning formulas
for compounds containing other elements. We used halogenated organic
compounds (HOC), a chemical class that is ubiquitous in nature as
well as anthropogenic systems, as an example to demonstrate the capability
of Formularity with IPA. A HOC standard mix was used to evaluate the
identification confidence of IPA. Tap water and HOC spike in Suwannee
River NOM were used to assess HOC identification in complex environmental
samples. Strategies for reconciliation of CIA and IPA assignments
were discussed. Software and sample databases with documentation are
freely available