Extended Data Fig. 3: Identification and localization of xanthommatin in light chromatophores.
From: Elucidating the control and development of skin patterning in cuttlefish
a, Chromatophores before (left) and after (right) local application of 40 μM glutamate. b, Transmission spectra of a population of chromatophores before (circles) and after (squares) glutamate application, projected onto two dimensions defined by human L and S cone action spectra (n = 63 chromatophores). c, Direct infusion electrospray ionization Fourier-transform ion cyclotron resonance (ESI-FT-ICR) mass spectrum of the skin tissue extract showing high spectral complexity. d, HPLC–UV–MS chromatograms of skin tissue extract showing two main peaks with correlating ultraviolet-light (250 nm) absorption (blue) and mass spectrometry intensity (grey) consisting of eluting compounds with m/z 380.09 and m/z 424.08 (extracted ion chromatogram (EIC) traces, green). Experiments were replicated five times with similar results. e, Direct infusion ESI-FT-ICR mass spectra of skin tissue extract showing an overlay of the isolated precursor spectrum for decarboxylated xanthommatin (green, m/z 380.0876, theoretical: m/z 380.0877) and the fragment spectrum (red). Main fragments were assigned to putative structural losses of A (-NH3), B (-H2O, -NH3), C (-NH3, -HCOOH), D (-C2H3NO2) by accurate mass. f, Direct infusion ESI-FT-ICR mass spectra of skin tissue extract showing an overlay of the isolated precursor spectrum for xanthommatin (green, m/z 424.0774, theoretical: m/z 424.0775) and the fragment spectrum (red). Main fragments were assigned to putative structural losses of A (-NH3), B (-H2O, -NH3), C (-NH3, -HCOOH), D (-C2H3NO2) by accurate mass. g, Intensity distributions in laser desorption ionization Fourier-transform ion cyclotron resonance mass spectrometry (LDI-FT-ICR-MS) imaging and structures for putative xanthommatin derivatives (merged [M + H]+; [M + Na]+): decarboxylated, oxidized (m/z 380.0886; 402.0696), decarboxylated, reduced (m/z 382.1037; 404.0853), oxidized (m/z 424.0785; 446.0629) and reduced (m/z 426.0938; 448.0761). h, Intensity distributions of main xanthommatin and derivative fragments, corresponding to molecular species detected in ESI-FT-ICR fragmentation measurements. Experiments were performed on 12 tissue slices, producing similar results. i, Image of cryotome section of fresh-frozen Sepia skin showing chromatophores. j, Spatial segmentation map of section in i, showing distinct clusters for light and dark chromatophores (orange versus black colours) and surrounding tissue (grey). k, Intensity distributions for xanthommatin derivatives (merged [M + H]+ and [M + Na]+) obtained from LDI-FT-ICR-MS imaging experiments (n = 1 sample).
