title: Mass spectrometry imaging of surface lipids on intact Drosophila melanogaster flies.
abstract: The spatial distribution of neutral lipids and semiochemicals on the surface of six-day-old separately reared naive Drosophila melanogaster flies has been visualized and studied using matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry and laser-assisted desorption/ionization (LDI)-TOF imaging (MSI). Metal targets were designed for two-dimensional MSI of the surface of 3-D biological objects. Targets with either simple grooves or profiled holes designed to accurately accommodate the male and female bodies were fabricated. These grooves and especially holes ensured correct height fixation and spatial orientation of the flies on the targets after matrix application and sample drying. For LDI-TOF to be used, the flies were arranged into holes and fixed to a plane of the target using fast-setting glue. In MALDI-TOF mode, the flies were fixed as above and sprayed with a lithium 2,5-dihydroxybenzoate matrix using up to 100 airbrush spray cycles. The scanning electron microscopy images revealed that the deposits of matrix were homogenous and the matrix formed mostly into the clusters of crystals (40-80 µm) that were separated from each other by an uncovered cuticle surface (30-40 µm). The MSI using target with profiled holes provided superior results to the targets with simple grooves, eliminating the ion suppression/mass deviation due to the 3-D shape of the flies. Attention was paid to neutral lipids and other compounds including the male anti-attractant 11-cis-vaccenyl acetate for which the expected distribution with high concentration on the tip of the male abdomen was confirmed. The red and blue mass shift (PlusMinus1 colour scale) was observed associated with mass deviation predominantly between ±0.2 and 0.3 Da. We use in-house developed software for mass recalibration, to eliminate the mass deviation effects and help with the detection of low-intensity mass signals.
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Science of the Czech Republic, v. v. i., Flemingovo nám. 2, CZ-166 10, Prague 6, Czech Republic; Department of Analytical Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030/8, CZ-128 43, Prague 2, Czech Republic; Max Planck Institute for Chemical Ecology, Hans-Knöll-Straße 8, D-07745, Jena, Germany.
authors.forename: Filip
authors.initials: F
authors.lastname: Kaftan
authors.forename: Vladimír
authors.initials: V
authors.lastname: Vrkoslav
authors.forename: Philipp
authors.initials: P
authors.lastname: Kynast
authors.forename: Purva
authors.initials: P
authors.lastname: Kulkarni
authors.forename: Sebastian
authors.initials: S
authors.lastname: Böcker
authors.forename: Josef
authors.initials: J
authors.lastname: Cvačka
authors.forename: Markus
authors.initials: M
authors.lastname: Knaden
authors.forename: Aleš
authors.initials: A
authors.lastname: Svatoš
mesh_terms: D000818:Animals; D004331:Drosophila melanogaster / Q000737:chemistry*; D005260:Female; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008055:Lipids / Q000032:analysis* / Q000737:chemistry*; D008297:Male; D013058:Mass Spectrometry / Q000379:methods*; D057054:Molecular Imaging / Q000379:methods*; D010675:Pheromones / Q000032:analysis / Q000737:chemistry
chemical_list: D008055:Lipids; D010675:Pheromones
keywords: MALDI; fruit flies; laser desorption; mass shift correction; mass spectrometric imaging; neutral lipids; sex pheromones