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.

Single-wall carbon nanotube field effect transistors (SWNT-FETs) are ideal candidates for fabricating sensors due to their unique electronic properties and have been widely investigated for chemical and biological sensing applications. The lack of selectivity of SWNT-FETs has prompted extensive research on developing ligands that exhibit specific binding as selective surface coating for SWNTs. Herein we describe the rational design of a peptide recognition element (PRE) that is capable of noncovalently attaching to SWNTs as well as binding to trinitrotoluene (TNT). The PRE contains two domains, a TNT binding domain derived from the binding pocket of the honeybee odor binding protein ASP1, and a SWNT binding domain previously identified from the phage peptide display library. The PRE structure in the presence of SWNT was investigated by performing classical all-atom molecular dynamics simulations, circular dichroism spectroscopy, and atomic force microscopy. Both computational and experimental analyses demonstrate that the peptide retains two functional domains for SWNT and TNT binding. The binding motif of the peptide to SWNT and to TNT was revealed from interaction energy calculations by molecular dynamics simulations. The potential application of the peptide for the detection of TNT is theoretically predicted and experimentally validated using a SWNT-FET sensor functionalized with a designer PRE. Results from this study demonstrate the creation of chemosensors using designed PRE as selective surface coatings for targeted analytes.

Many cephalopods exhibit remarkable dermal iridescence, a component of their complex, dynamic camouflage and communication. In the species Euprymna scolopes, the lightorgan iridescence is static and is due to reflectin protein-based platelets assembled into lamellar thin-film reflectors called iridosomes, contained within iridescent cells called iridocytes. Squid in the family Loliginidae appear to be unique in which the dermis possesses a dynamic iridescent component with reflective, coloured structures that are assembled and disassembled under the control of the muscarinic cholinergic system and the associated neurotransmitter acetylcholine (ACh). Here we present the sequences and characterization of three new members of the reflectin family associated with the dynamically changeable iridescence in Loligo and not found in static Euprymna iridophores. In addition, we show that application of genistein, a protein tyrosine kinase inhibitor, suppresses ACh-and calciuminduced iridescence in Loligo. We further demonstrate that two of these novel reflectins are extensively phosphorylated in concert with the activation of iridescence by exogenous ACh. This phosphorylation and the correlated iridescence can be blocked with genistein. Our results suggest that tyrosine phosphorylation of reflectin proteins is involved in the regulation of dynamic iridescence in Loligo.

This tutorial review provides an overview of bio-directed synthesis of nanomaterials, starting with the foundation of biomineralization research--how organisms are able to biomineralize materials in vivo--and progressing to studies of biomineralization in vitro. This research is of interest to biologists, chemists and materials scientists alike, especially in light of efforts to find 'greener' methods of inorganic material synthesis. Examples of applications of nanomaterials synthesized by these methods are provided to demonstrate the end goals of biomineralization research.

Reflectins are a unique group of structural proteins involved in dynamic optical systems in cephalopods that modulate incident light or bioluminescence. We describe cloning, structural characterization, and optical properties of a reflectin‐based domain, refCBA, from reflectin 1a of Hawaiian bobtail squid, Euprymna scolopes. Thin films created from the recombinant protein refCBA display interesting optical features when the recombinant protein is appropriately organized. RefCBA was cloned and expressed as a soluble protein enabling purification, with little structural organization found using Fourier transform infrared spectroscopy and circular dichroism. Single‐layer and multi‐layer thin films of refCBA were then produced by flow coating and spin coating, and displayed colors due to thin film interference. Diffraction experiments showed the assemblies were ordered enough to work as diffraction gratings to generate diffraction patterns. Nano‐spheres and lamellar microstructures of refCBA samples were observed by scanning electron microscopy and atomic force microscopy. Despite the reduced complexity of the refCBA protein compared to natural reflectins, unique biomaterials with similar properties to reflectins were generated by self‐assembled reflectin‐based refCBA molecules. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013