The self-organizing properties of squid reflectin protein

Abstract

Reflectins, a recently identified protein family that is enriched in aromatic and sulphur-containing amino acids, are used by certain cephalopods to manage and manipulate incident light in their environment. These proteins are the predominant constituent of nanoscaled photonic structures that function in static and adaptive colouration, extending visual performance and intra-species communication. Our investigation into recombinantly expressed reflectin has revealed unanticipated self-assembling and behavioural properties, and we demonstrate that reflectin can be easily processed into thin films, photonic grating structures and fibres. Our findings represent a key step in our understanding of the property-function relationships of this unique family of reflective proteins.

Changes in reflectin protein phosphorylation are associated with dynamic iridescence in squid

“…Because nicotinictype receptors that characterize the neuromuscular junction do not affect dynamic iridescence, this optical change is not attributed to muscular contraction, as is the case for chromatophore signalling in squid (Messenger 2001;Mäthger et al 2004). In addition, isolated reflectin proteins exhibit unusual solubility and selfassociation properties (Kramer et al 2007). All these data suggest that the proteinaceous nature of iridosomes in loliginids may contribute to their dynamic ability to modulate their iridescent effects.…”

Do cephalopods communicate using polarized light reflections from their skin?

“…The angle of maximum polarization (μ) can easily be derived from Brewster's law (μ=tan n b /n a , where n a and n b are the refractive indices of a plate and space, respectively). For a squid multilayer reflector consisting of protein plates [n a =1.59 (Kramer et al, 2007)] and cytoplasm spaces [n b =1.33 (Denton and Land, 1971) (Mäthger et al, 2009)] have a distinct stripe of iridophores along their dorso-lateral sides (called 'red' stripes). These iridophores have most of their reflective plates oriented parallel to the skin surface.…”

“…Chromatophores can expand and retract over the iridophores, and thus influence both the light that reaches the iridophores and the light reflected from the iridophores before it exits the skin (Hanlon, 1982;Mäthger and Hanlon, 2007;Williams, 1909). Iridophores are composed of stacks of protein plates interspersed by spaces of cytoplasm, each differing in refractive index (Denton and Land, 1971;Kramer et al, 2007). The series of plates and spaces acts as a multilayer interference reflector (Land, 1972), which reflects specific wavelengths depending on the thickness of the plates and spaces.…”

Biomimetic virus-based colourimetric sensors

“…Inspired by nature, sensors are being developed that change colour in response to target chemicals by employing biomimetic structures and mechanisms. In particular, structurally coloured biomaterials, such as butterfly wings, beetle exocuticles, cephalopod skins, mammalian skins and avian skins/feathers [6][7][8][9][10][11][12][13][14] , provide insight into developing colourimetric sensors. These materials exhibit brilliant colours that are derived from their hierarchically organized structures and are resistant to photobleaching 7 .…”