title: Metabolite localization by atmospheric pressure high-resolution scanning microprobe matrix-assisted laser desorption/ionization mass spectrometry imaging in whole-body sections and individual organs of the rove beetle Paederus riparius.
abstract: Mass spectrometry imaging provides for non-targeted, label-free chemical imaging. In this study, atmospheric pressure high-resolution scanning microprobe matrix-assisted laser desorption/ionization mass spectrometry imaging (AP-SMALDI MSI) was used for the first time to describe the chemical distribution of the defensive compounds pederin, pseudopederin, and pederon in tissue sections (16 μm thick) of the rove beetle Paederus riparius. The whole-insect tissue section was scanned with a 20-μm step size. Mass resolution of the orbital trapping mass spectrometer was set to 100,000 at m/z 200. Additionally, organ-specific compounds were identified for brain, nerve cord, eggs, gut, ovaries, and malpighian tubules. To confirm the distribution of the specific compounds, individual organs from the insect were dissected, and MSI experiments were performed on the dissected organs. Three ganglia of the nerve cord, with a dimension of 250-500 μm, were measured with 10-μm spatial resolution. High-quality m/z images, based on high spatial resolution and high mass accuracy were generated. These features helped to assign mass spectral peaks with high confidence. Mass accuracy of the imaging experiments was <3 ppm root mean square error, and mapping of different compound classes from a single experiment was possible. This approach improved the understanding of the biochemistry of P. riparius. Concentration differences and distributions of pederin and its analogues could be visualized in the whole-insect section. Without any labeling, we assigned key lipids for specific organs to describe their location in the body and to identify morphological structures with a specificity higher than with staining or immunohistology methods.
authors.affiliation: Institute of Inorganic and Analytical Chemistry, Justus Liebig University Giessen, Schubertstraße 60, Building 16, 35392, Giessen, Germany.
authors.forename: Dhaka Ram
authors.initials: DR
authors.lastname: Bhandari
authors.forename: Matthias
authors.initials: M
authors.lastname: Schott
authors.forename: Andreas
authors.initials: A
authors.lastname: Römpp
authors.forename: Andreas
authors.initials: A
authors.lastname: Vilcinskas
authors.forename: Bernhard
authors.initials: B
authors.lastname: Spengler
mesh_terms: D000825:Animal Structures / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D001517:Coleoptera / Q000737:chemistry* / Q000378:metabolism; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry; D011714:Pyrans / Q000737:chemistry / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods; D053719:Tandem Mass Spectrometry / Q000379:methods*; D051598:Whole Body Imaging / Q000379:methods*
chemical_list: D008055:Lipids; D011714:Pyrans; C100127:pederin