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

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