4800 imaging application

A model 4800 MALDI-TOF/TOF analyzer (Applied Biosystems, Framingham, MA) equipped with a 200 Hz, 355 nm Nd:YAG laser was used for extract quantitation and tissue imaging. Image acquisition was performed with the 4800 Imaging application (Novartis, Basel, Switzerland).

MALDI imaging of C. sapidus and C. maenas PO was performed as previously described [38 (link)]. Briefly, the PO was rinsed in water immediately following dissection to eliminate salt content. It was then positioned on a MALDI plate and placed in a desiccator to dry on the plate without being frozen or sectioned. Before imaging acquisition, five coats of DHB (150 mg/mL in 50% methanol, v/v) were applied on the tissue surface using an airbrush (Paasche Airbrush Company, Chicago, IL, USA) with 30 s of drying time between each coat. Imaging acquisition was performed on the model 4800 MALDI TOF/TOF analyzer (Applied Biosystems, Framingham, MA, USA) controlled using the 4800 Imaging application (Novartis, Basel, Switzerland) available through the MALDI MSI website (www.maldi-msi.org). To generate images, spectra were collected at 100 µm intervals in both the x and y dimensions across the surface of the sample. Each mass spectrum was generated by averaging 200 laser shots over the mass range m/z 800–2000. Individual spectra were acquired using 1.0 ns binning to yield 27812 data points per spectrum. Image files were then processed and extracted ion images were created using the TissueView software package (Applied Biosystems, Framingham, MA, USA).