Reconfigurable Infrared Camouflage Coatings from a Cephalopod Protein

Phan, Long; Walkup, Ward G.; Ordinario, David D.; Karshalev, Emil; Jocson, Jonah‐Micah; Burke, Anthony M.; Gorodetsky, Alon A.

doi:10.1002/adma.201301472

Cited by 179 publications

(191 citation statements)

References 31 publications

(72 reference statements)

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“…D. opalescens iridocytes contain four types of reflectin proteins, A1, A2, B, and C, that vary in length, composition, and the number and locations of reflectin motifs. Prior investigations have revealed interesting optical and proton-conducting properties of thin films of these recombinant proteins and their peptide fragments, with consistent observations of low solubility and an absence of any significant secondary structure (15)(16)(17)(18)(19). Given their low sequence complexity and lack of large hydrophobic residues necessary for folding, reflectins can be categorized within the increasingly important class of intrinsically disordered proteins.…”

mentioning

confidence: 71%

Cyclable Condensation and Hierarchical Assembly of Metastable Reflectin Proteins, the Drivers of Tunable Biophotonics

Levenson

Bracken

Bush

et al. 2016

Journal of Biological Chemistry

138

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Reversible changes in the phosphorylation of reflectin proteins have been shown to drive the tunability of color and brightness of light reflected from specialized cells in the skin of squids and related cephalopods. We show here, using dynamic light scattering, electron microscopy, and fluorescence analyses, that reversible titration of the excess positive charges of the reflectins, comparable with that produced by phosphorylation, is sufficient to drive the reversible condensation and hierarchical assembly of these proteins. The results suggest a two-stage process in which charge neutralization first triggers condensation, resulting in the emergence of previously cryptic structures that subsequently mediate reversible, hierarchical assembly. The extent to which cyclability is seen in the in vitro formation and disassembly of complexes estimated to contain several thousand reflectin molecules suggests that intrinsic sequence-and structure-determined specificity governs the reversible condensation and assembly of the reflectins and that these processes are therefore sufficient to produce the reversible changes in refractive index, thickness, and spacing of the reflectin-containing subcellular Bragg lamellae to change the brightness and color of reflected light. This molecular mechanism points to the metastability of reflectins as the centrally important design principle governing biophotonic tunability in this system. Cephalopods (squids, octopi, and cuttlefish) are well known for their diversity of light-manipulating, pigment-based, and nano-structural systems used for camouflage and underwater communication (1, 2). Of these systems, the dynamically tunable structural color of certain squids holds great interest as models for next-generation tunable optical materials and devices (3, 4). Reflectins are a class of proteins originally identified in the reflective tissue of the Hawaiian bobtail squid, Euprymna scolopes (5), and have since been found in multiple squid species, including the pelagic Pacific and Atlantic squids Doryteuthis opalescens and Doryteuthis pealeii, respectively (6 -8). In these latter two species, the reflectins constitute the principal constituents of the dynamically controlled subcellular Bragg reflector lamellae responsible for the tunable color and intensity of reflected light in "iridocyte" cells (8) and the subcellular vesicles responsible for switchable bright white Mie scattering in specialized "leucophore" cells in females of the Pacific species (the only example, to our knowledge, of switchable broadband reflectance in molluscs) (6). Reflectins are also found, although in a different molar ratio, in the static (nontunable) Bragg lamellae of fixed-color iridocytes in this species (7).Reflectance from both the tunable iridocytes and switchable leucophores is activated by the diffusion of acetylcholine (ACh) 2 (8, 9), recently discovered to be released from fine neuronal processes innervating local areas of the squid skin (10). In the tunable iridocytes, it has been shown that the act...

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confidence: 71%

Cyclable Condensation and Hierarchical Assembly of Metastable Reflectin Proteins, the Drivers of Tunable Biophotonics

Levenson

Bracken

Bush

et al. 2016

Journal of Biological Chemistry

138

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“…[16][17][18][19][20] Within this context, a number of literature reports have investigated the properties of unique structural proteins known as reectins, [7][8][9][10]14,[16][17][18][21][22][23][24] which are found in cephalopod skin cells (i.e. leucophores, iridophores, and chromatophores).…”

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confidence: 99%

Production and electrical characterization of the reflectin A2 isoform from Doryteuthis (Loligo) pealeii

et al. 2016

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Cephalopods have recently emerged as a source of inspiration for the development of novel functional materials. Within this context, a number of studies have explored structural proteins known as reflectins, which play a key role in cephalopod adaptive coloration in vivo and exhibit interesting properties in vitro. Herein, we report an improved high-yield strategy for the preparation and isolation of reflectins in quantities sufficient for materials applications. We first select the Doryteuthis (Loligo) pealeii reflectin A2 (RfA2) isoform as a "model" system and validate our approach for the expression and purification of this protein. We in turn fabricate RfA2-based twoterminal devices and employ both direct and alternating current measurements to demonstrate that RfA2 films conduct protons. Our findings underscore the potential of reflectins as functional materials and may allow a wider range of researchers to investigate their properties.Cephalopods (squid, octopuses, and cuttlesh) are well known for their sophisticated neurophysiology, complex behavior, and stunning camouage displays.1-6 Recently, these animals have drawn signicant attention as sources of novel materials for optical systems, 7-10 biomedical technologies, 11-15 and bioelectronic devices. [16][17][18][19][20] Within this context, a number of literature reports have investigated the properties of unique structural proteins known as reectins, [7][8][9][10]14,[16][17][18][21][22][23][24] which are found in cephalopod skin cells (i.e. leucophores, iridophores, and chromatophores). [25][26][27][28][29][30] In vivo, reectins in general have been shown to play important roles in cephalopod adaptive coloration by serving as components of optically-active ultrastructures, including layered stacks of membrane-enclosed platelets in iridophores, 25,26 membrane-bound arrangements of spherical microparticles in leucophores, 27,28 and interconnected networks of pigment granules in chromatophores. 29,30 In vitro, the Doryteuthis (Loligo) pealeii reectin A1 (RfA1) isoform has found applications in recongurable infrared camouage coatings that are actuated by chemical and mechanical stimuli, 7,8 proton-conducting lms with electrical gures of merit rivaling those of some articial analogues, 16-18 and biocompatible substrates that support the proliferation and differentiation of neural stem cells.14 Overall, reectins' fascinating properties have provided a strong impetus for their continued exploration from both fundamental and applied perspectives.Herein, we describe an improved methodology for the production of difficult-to-handle reectins in quantities sufficient for materials applications. We rst select the Doryteuthis (Loligo) pealeii reectin A2 (RfA2) isoform as a "model" system for electrical characterization and validate a new high-yield strategy for the expression and purication of this precipitation-prone protein. We subsequently fabricate and characterize two-terminal devices for which RfA2 thin lms constitute the active layer. We in tu...

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“…20,21 We first extracted crude reflectin from E. coli inclusion bodies. The protein was then sequentially purified by immobilized metal affinity chromatography under denaturing conditions and high performance liquid chromatography (HPLC).…”

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confidence: 99%

“…Recently, our group discovered that reflectin, a structural protein that plays a key role in the color-changing abilities of cephalopods, [16][17][18][19][20] is an effective proton conducting material. 21 This finding enabled the fabrication of protein-based protonic transistors with excellent figures of merit, including a proton mobility (µ H+ ) of ∼7.3 × 10 −3 cm 2 V −1 s −1 .…”

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Protonic transistors from thin reflectin films

Ordinario¹,

Phan²,

Jocson³

et al. 2014

APL Materials

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Ionic transistors from organic and biological materials hold great promise for bioelectronics applications. Thus, much research effort has focused on optimizing the performance of these devices. Herein, we experimentally validate a straightforward strategy for enhancing the high to low current ratios of protein-based protonic transistors. Upon reducing the thickness of the transistors’ active layers, we increase their high to low current ratios 2-fold while leaving the other figures of merit unchanged. The measured ratio of 3.3 is comparable to the best values found for analogous devices. These findings underscore the importance of the active layer geometry for optimum protonic transistor functionality.

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Reconfigurable Infrared Camouflage Coatings from a Cephalopod Protein

Cited by 179 publications

References 31 publications

Cyclable Condensation and Hierarchical Assembly of Metastable Reflectin Proteins, the Drivers of Tunable Biophotonics

Cyclable Condensation and Hierarchical Assembly of Metastable Reflectin Proteins, the Drivers of Tunable Biophotonics

Production and electrical characterization of the reflectin A2 isoform from Doryteuthis (Loligo) pealeii

Protonic transistors from thin reflectin films

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