Contributions of Phenoxazone-Based Pigments to the Structure and Function of Nanostructured Granules in Squid Chromatophores

Abstract

Understanding the structure-function relationships of pigment-based nanostructures can provide insight into the molecular mechanisms behind biological signaling, camouflage, or communication experienced in many species. In squid Doryteuthis pealeii, combinations of phenoxazone-based pigments are identified as the source of visible color within the nanostructured granules that populate dermal chromatophore organs. In the absence of the pigments, granules experience a reduction in diameter with the loss of visible color, suggesting important structural and functional features. Energy gaps are estimated from electronic absorption spectra, revealing highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energies that are dependent upon the varying carboxylated states of the pigment. These results implicate a hierarchical mechanism for the bulk coloration in cephalopods originating from the molecular components confined within in the nanostructured granules of chromatophore organs.

Ommochromes in invertebrates: biochemistry and cell biology

“…Other chromes, like melanins and pterins, and structural colours, such as in butterfly wing scales, can alter the chemical colours of ommochromes (Stavenga, Leertouwer & Wilts, ; Wilts et al, ). Colour patterns associated with ommochromes and their precursors are involved in crypsis (Williams et al, ), mimicry (Reed, McMillan & Nagy, ; Ferguson & Jiggins, ; Bybee et al, ), colour changes (Insausti & Casas, ; Llandres et al, ; Umbers et al, ; Williams et al, ), sexual maturation and seasonal forms (Nijhout, ; Futahashi et al, ), as well as many other colour‐based functions.…”

Optical extinction of size-controlled aerosols generated from squid chromatophore pigments

“…2 In cephalopods, protein-based nanostructured granules populate the chromatophore and leucophore (cuttlefish and octopus only) organs in their dermal tissue and contribute to pigmentary color and diffuse scattering, respectively. [3][4][5][6][7] While many of the components integral to the optical function of these organs have been identified, the relationship between chemical composition and structural morphology remains largely unknown. This is especially true for the chromatophore granules, where proteins and pigments are both associated with granule structure and function; 5,6 yet, it is still unclear how they coordinate together within a nanoparticle.…”

“…6 When pigments are selectively removed, granule diameter reduces by ∼70%, and the remaining solution is devoid of color. To better understand the structure dependent function of these pigments, we first set out to manufacture pure pigment nanoparticles.…”

“…6,14 The extracted solution is dried in a vacuum desiccator overnight and used to make a 1.00% (w/w) solution in 0.20M hydrochloric acid (HCl). The acidic pigment solution is then placed in the intake tube of a Collison-type atomizer (Fig.…”

“…Even though these measurements do not account for the full makeup of the native chromatophore granules, the pigment is a major component, 6 and, therefore, a dominant contributor to the optical behavior. By exploiting their ability to assemble into nanostructures in the gas phase, we also show a new method for processing these pigments that can conceivably be scaled up for spray-on coatings.…”