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Thackston, KA, Deheyn DD, Sievenpiper DF.  2019.  Simulation of electric fields generated from microtubule vibrations. Physical Review E. 100   10.1103/PhysRevE.100.022410   AbstractWebsite

Microtubules are tubular proteins that form part of the cytoskeleton in eukaryotic cells. Because of their unique mechanical properties, many studies have theorized microtubules could show high-frequency mechanical vibrations. Others have further suggested these vibrations of the electrically polar microtubules could be a source of electric fields inside the cell that could serve some biological function, such as a role in organizing mitosis or also possibly in cell-to-cell communication. In this work, we use a transient method to simulate the electric fields that would be generated from a single microtubule supposing they could sustain vibrations. We evaluate the biological significance of the electric fields and the potential energy microtubules might exert on one another. Our simulation method allows us to evaluate vibrational modes that have not previously been studied. The simulations suggest the acoustic branch flexing mode would actually be the most electrically active. Our results suggest a single vibrating microtubule could potentially exert significant forces (those that exceed thermal energy) on biological dipoles or charges at distances larger then the Debye length, on the order of 10 nm from the surface of the microtubule, but interaction is not likely at greater distances.

Lewis, VM, Saunders LM, Larson TA, Bain EJ, Sturiale SL, Gur D, Chowdhury S, Flynn JD, Allen MC, Deheyn DD, Lee JC, Simon JA, Lippincott-Schwartz J, Raible DW, Parichy DM.  2019.  Fate plasticity and reprogramming in genetically distinct populations of Danio leucophores. Proceedings of the National Academy of Sciences of the United States of America. 116:11806-11811.   10.1073/pnas.1901021116   AbstractWebsite

Understanding genetic and cellular bases of adult form remains a fundamental goal at the intersection of developmental and evolutionary biology. The skin pigment cells of vertebrates, derived from embryonic neural crest, are a useful system for elucidating mechanisms of fate specification, pattern formation, and how particular phenotypes impact organismal behavior and ecology. In a survey of Danio fishes, including the zebrafish Danio rerio, we identified two populations of white pigment cells-leucophores-one of which arises by transdifferentiation of adult melanophores and another of which develops from a yellow-orange xanthophore or xanthophore-like progenitor. Single-cell transcriptomic, mutational, chemical, and ultrastructural analyses of zebrafish leucophores revealed cell-type-specific chemical compositions, organelle configurations, and genetic requirements. At the organismal level, we identified distinct physiological responses of leucophores during environmental background matching, and we showed that leucophore complement influences behavior. Together, our studies reveal independently arisen pigment cell types and mechanisms of fate acquisition in zebrafish and illustrate how concerted analyses across hierarchical levels can provide insights into phenotypes and their evolution.

Velasco-Hogan, A, Deheyn DD, Koch M, Nothdurft B, Arzt E, Meyers MA.  2019.  On the nature of the transparent teeth of the deep-sea dragonfish, Aristostomias scintillans. Matter. : Elsevier   10.1016/j.matt.2019.05.010   Abstract

The dragonfish is a voracious predator of the deep sea with an arsenal of tools to hunt prey and remain concealed. In contrast to its dark pigmented skin, the dragonfish is equipped with transparent teeth. Here, we establish the structure, composition, and mechanical properties of the transparent teeth for the first time. We find the enamel-like layer to consist of nanocrystalline hydroxyapatite domains (?20 nm grain size) embedded in an amorphous matrix, whereas in the dentin layer the nanocrystalline hydroxyapatite coats nanoscale collagen fibrils forming nanorods. This nanoscale structure is responsible for the much-reduced Rayleigh light scattering, which is further ensured by the sufficiently thin walls. Here, we suggest that the nanostructured design of the transparent dragonfish teeth enables predatory success as it makes its wide-open mouth armed with saber-like teeth effectively disappear, showing no contrast to the surrounding blackness of the fish nor the background darkness of the deep sea.

Hartmann, AC, Marhaver KL, Klueter A, Lovci MT, Closek CJ, Diaz E, Chamberland VF, Archer FI, Deheyn DD, Vermeij MJA, Medina M.  2019.  Acquisition of obligate mutualist symbionts during the larval stage is not beneficial for a coral host. Molecular Ecology. 28:141-155.   10.1111/mec.14967   AbstractWebsite

Theory suggests that the direct transmission of beneficial endosymbionts (mutualists) from parents to offspring (vertical transmission) in animal hosts is advantageous and evolutionarily stable, yet many host species instead acquire their symbionts from the environment (horizontal acquisition). An outstanding question in marine biology is why some scleractinian corals do not provision their eggs and larvae with the endosymbiotic dinoflagellates that are necessary for a juvenile's ultimate survival. We tested whether the acquisition of photosynthetic endosymbionts (family Symbiodiniaceae) during the planktonic larval stage was advantageous, as is widely assumed, in the ecologically important and threatened Caribbean reef-building coral Orbicella faveolata. Following larval acquisition, similar changes occurred in host energetic lipid use and gene expression regardless of whether their symbionts were photosynthesizing, suggesting the symbionts did not provide the energetic benefit characteristic of the mutualism in adults. Larvae that acquired photosymbionts isolated from conspecific adults on their natal reef exhibited a reduction in swimming, which may interfere with their ability to find suitable settlement substrate, and also a decrease in survival. Larvae exposed to two cultured algal species did not exhibit differences in survival, but decreased their swimming activity in response to one species. We conclude that acquiring photosymbionts during the larval stage confers no advantages and can in fact be disadvantageous to this coral host. The timing of symbiont acquisition appears to be a critical component of a host's life history strategy and overall reproductive fitness, and this timing itself appears to be under selective pressure.

d'Auriac, IG, Quinn RA, Maughan H, Nothias LF, Little M, Kapono CA, Cobian A, Reyes BT, Green K, Quistad SD, Leray M, Smith JE, Dorrestein PC, Rohwer F, Deheyn DD, Hartmann AC.  2018.  Before platelets: the production of platelet-activating factor during growth and stress in a basal marine organism. Proceedings of the Royal Society B-Biological Sciences. 285   10.1098/rspb.2018.1307   AbstractWebsite

Corals and humans represent two extremely disparate metazoan lineages and are therefore useful for comparative evolutionary studies. Two lipid-based molecules that are central to human immunity, platelet-activating factor (PAF) and Lyso-PAF were recently identified in scleractinian corals. To identify processes in corals that involve these molecules, PAF and Lyso-PAF biosynthesis was quantified in conditions known to stimulate PAF production in mammals (tissue growth and exposure to elevated levels of ultraviolet light) and in conditions unique to corals (competing with neighbouring colonies over benthic space). Similar to observations in mammals, PAF production was higher in regions of active tissue growth and increased when corals were exposed to elevated levels of ultraviolet light. PAF production also increased when corals were attacked by the stinging cells of a neighbouring colony, though only the attacked coral exhibited an increase in PAF. This reaction was observed in adjacent areas of the colony, indicating that this response is coordinated across multiple polyps including those not directly subject to the stress. PAF and Lyso-PAF are involved in coral stress responses that are both shared with mammals and unique to the ecology of cnidarians.

Christianson, C, Goldberg NN, Deheyn DD, Cai SQ, Tolley MT.  2018.  Translucent soft robots driven by frameless fluid electrode dielectric elastomer actuators. Science Robotics. 3   10.1126/scirobotics.aat1893   AbstractWebsite

Dielectric elastomer actuators (DEAs) are a promising enabling technology for a wide range of emerging applications, including robotics, artificialmuscles, and microfluidics. This is due to their large actuation strains, rapid response rate, low cost and low noise, high energy density, and high efficiency when compared with alternative actuators. These properties make DEAs ideal for the actuation of soft submersible devices, although their use has been limited because of three main challenges: (i) developing suitable, compliant electrodematerials; (ii) the need to effectively insulate the actuator electrodes from the surrounding fluid; and (iii) the rigid frames typically required to prestrain the dielectric layers. We explored the use of a frameless, submersible DEA design that uses an internal chamber filled with liquid as one of the electrodes and the surrounding environmental liquid as the second electrode, thus simplifying the implementation of soft, actuated submersible devices. We demonstrated the feasibility of this approach with a prototype swimming robot composed of transparent bimorph actuator segments and inspired by transparent eel larvae, leptocephali. This design achieved undulatory swimming with a maximum forward swimming speed of 1.9 millimeters per second and a Froude efficiency of 52%. We also demonstrated the capability for camouflage and display through the body of the robot, which has an average transmittance of 94% across the visible spectrum, similar to a leptocephalus. These results suggest a potential for DEAs with fluid electrodes to serve as artificial muscles for quiet, translucent, swimming soft robots for applications including surveillance and the unobtrusive study of marine life.

De Meulenaere, E, Bailey JB, Tezcan FA, Deheyn DD.  2017.  First biochemical and crystallographic characterization of a fast-performing ferritin from a marine invertebrate. Biochemical Journal. 474:4193-4206.   10.1042/bcj20170681   AbstractWebsite

Ferritin, a multimeric cage-like enzyme, is integral to iron metabolism across all phyla through the sequestration and storage of iron through efficient ferroxidase activity. While ferritin sequences from similar to 900 species have been identified, crystal structures from only 50 species have been reported, the majority from bacterial origin. We recently isolated a secreted ferritin from the marine invertebrate Chaetopterus sp. (parchment tube worm), which resides in muddy coastal seafloors. Here, we present the first ferritin from a marine invertebrate to be crystallized and its biochemical characterization. The initial ferroxidase reaction rate of recombinant Chaetopterus ferritin (ChF) is 8-fold faster than that of recombinant human heavy-chain ferritin (HuHF). To our knowledge, this protein exhibits the fastest catalytic performance ever described for a ferritin variant. In addition to the high-velocity ferroxidase activity, ChF is unique in that it is secreted by Chaetopterus in a bioluminescent mucus. Previous work has linked the availability of Fe2+ to this long-lived bioluminescence, suggesting a potential function for the secreted ferritin. Comparative biochemical analyses indicated that both ChF and HuHF showed similar behavior toward changes in pH, temperature, and salt concentration. Comparison of their crystal structures shows no significant differences in the catalytic sites. Notable differences were found in the residues that line both 3-fold and 4-fold pores, potentially leading to increased flexibility, reduced steric hindrance, or a more efficient pathway for Fe2+ transportation to the ferroxidase site. These suggested residues could contribute to the understanding of iron translocation through the ferritin shell to the ferroxidase site.

Hsiung, BK, Siddique RH, Stavenga DG, Otto JC, Allen MC, Liu Y, Lu YF, Deheyn DD, Shawkey MD, Blackledge TA.  2017.  Rainbow peacock spiders inspire miniature super-iridescent optics. Nature Communications. 8   10.1038/s41467-017-02451-x   AbstractWebsite

Colour produced by wavelength-dependent light scattering is a key component of visual communication in nature and acts particularly strongly in visual signalling by structurally-coloured animals during courtship. Two miniature peacock spiders (Maratus robinsoni and M. chrysomelas) court females using tiny structured scales (similar to 40 x 10 mu m(2)) that reflect the full visual spectrum. Using TEM and optical modelling, we show that the spiders' scales have 2D nanogratings on microscale 3D convex surfaces with at least twice the resolving power of a conventional 2D diffraction grating of the same period. Whereas the long optical path lengths required for light-dispersive components to resolve individual wavelengths constrain current spectrometers to bulky sizes, our nano-3D printed prototypes demonstrate that the design principle of the peacock spiders' scales could inspire novel, miniature light-dispersive components.

Weigand, WJ, Messmore A, Tu J, Morales-Sanz A, Blair DL, Deheyn DD, Urbach JS, Robertson-Anderson RM.  2017.  Active microrheology determines scale-dependent material properties of Chaetopterus mucus. Plos One. 12   10.1371/journal.pone.0176732   AbstractWebsite

We characterize the lengthscale-dependent rheological properties of mucus from the ubiquitous Chaetopterus marine worm. We use optically trapped probes (2-10 mu m) to induce microscopic strains and measure the stress response as a function of oscillation amplitude. Our results show that viscoelastic properties are highly dependent on strain scale (l), indicating three distinct lengthscale-dependent regimes at l(1)<= 4 mu m, l(2)approximate to 4-10 mu m, and l(3)>= 10 mu m. While mucus response is similar to water for l(1), suggesting that probes rarely contact the mucus mesh, the response for l(2) is distinctly more viscous and independent of probe size, indicative of continuum mechanics. Only for l(3) does the response match the macroscopic elasticity, likely due to additional stiffer constraints that strongly resist probe displacement. Our results suggest that, rather than a single lengthscale governing crossover from viscous to elastic, mucus responds as a hierarchical network with a loose biopolymer mesh coupled to a larger scaffold responsible for macroscopic gel-like mechanics.

Lowder, KB, Allen MC, Day JMD, Deheyn DD, Taylor JRA.  2017.  Assessment of ocean acidification and warming on the growth, calcification, and biophotonics of a California grass shrimp. Ices Journal of Marine Science. 74:1150-1158.   10.1093/icesjms/fsw246   AbstractWebsite

Cryptic colouration in crustaceans, important for both camouflage and visual communication, is achieved through physiological and morphological mechanisms that are sensitive to changes in environmental conditions. Consequently, ocean warming and ocean acidification can affect crustaceans' biophotonic appearance and exoskeleton composition in ways that might disrupt colouration and transparency. In the present study, we measured growth, mineralization, transparency, and spectral reflectance (colouration) of the caridean grass shrimp Hippolyte californiensis in response to pH and temperature stressors. Shrimp were exposed to ambient pH and temperature (pH 8.0, 17 degrees C), decreased pH (pH 7.5, 17 degrees C), and decreased pH/increased temperature (pH 7.5, 19 degrees C) conditions for 7 weeks. There were no differences in either Mg or Ca content in the exoskeleton across treatments nor in the transparency and spectral reflectance. There was a small but significant increase in percent growth in the carapace length of shrimp exposed to decreased pH/increased temperature. Overall, these findings suggest that growth, calcification, and colour of H. californiensis are unaffected by decreases of 0.5 pH units. This tolerance might stem from adaptation to the highly variable pH environment that these grass shrimp inhabit, highlighting the multifarious responses to ocean acidification, within the Crustacea.

Tresguerres, M, Barott K, Barron ME, Deheyn D, Kline D, Linsmayer LB.  2017.  Cell Biology of Reef-Building Corals: Ion Transport, Acid/Base Regulation, and Energy Metabolism. Acid-Base Balance and Nitrogen Excretion in Invertebrates. ( Weihrauch D, O'Donnell M, Eds.).:193-218.: Springer International Publishing   10.1007/978-3-319-39617-0_7   Abstract

Coral reefs are built by colonial cnidarians that establish a symbiotic relationship with dinoflagellate algae of the genus Symbiodinium. The processes of photosynthesis, calcification, and general metabolism require the transport of diverse ions across several cellular membranes and generate waste products that induce acid/base and oxidative stress. This chapter reviews the current knowledge on coral cell biology with a focus on ion transport and acid/base regulation while also discussing related aspects of coral energy metabolism.

Colvin, MA, Hentschel BT, Deheyn DD.  2016.  Combined effects of water flow and copper concentration on the feeding behavior, growth rate, and accumulation of copper in tissue of the infaunal polychaete Polydora cornuta. Ecotoxicology. 25:1720-1729.   10.1007/s10646-016-1705-z   AbstractWebsite

We performed an experiment in a laboratory flume to test the effects of water flow speed and the concentration of aqueaous copper on the feeding behavior, growth rate, and accumulation of copper in the tissues of juvenile polychaetes Polydora cornuta. The experiment included two flow speeds (6 or 15 cm/s) and two concentrations of added copper (0 or 85 mu g/L). Worms grew significantly faster in the faster flow and in the lower copper concentration. In the slower flow, the total time worms spent feeding decreased significantly as copper concentration increased, but copper did not significantly affect the time worms spent feeding in the faster flow. Across all treatments, there was a significant, positive relationship between the time individuals spent feeding and their relative growth rate. Worms were observed suspension feeding significantly more often in the faster flow and deposit feeding significantly more often in the slower flow, but copper concentration did not affect the proportion of time spent in either feeding mode. The addition of 85 mu g/L copper significantly increased copper accumulation in P. cornuta tissue, but the accumulation did not differ significantly due to flow speed. There was a significant interaction between copper and flow; the magnitude of the difference in copper accumulation between the 0 and 85 mu g/L treatments was greater in the faster flow than in the slower flow. In slow flows that favor deposit feeding, worms grow slowly and accumulate less copper in their tissue than in faster flows that favor suspension feeding and faster growth.

deVries, MS, Webb SJ, Tu J, Cory E, Morgan V, Sah RL, Deheyn DD, Taylor JRA.  2016.  Stress physiology and weapon integrity of intertidal mantis shrimp under future ocean conditions. Scientific Reports. 6   10.1038/srep38637   AbstractWebsite

Calcified marine organisms typically experience increased oxidative stress and changes in mineralization in response to ocean acidification and warming conditions. These effects could hinder the potency of animal weapons, such as the mantis shrimp's raptorial appendage. The mechanical properties of this calcified weapon enable extremely powerful punches to be delivered to prey and aggressors. We examined oxidative stress and exoskeleton structure, mineral content, and mechanical properties of the raptorial appendage and the carapace under long-term ocean acidification and warming conditions. The predatory appendage had significantly higher % Mg under ocean acidification conditions, while oxidative stress levels as well as the % Ca and mechanical properties of the appendage remained unchanged. Thus, mantis shrimp tolerate expanded ranges of pH and temperature without experiencing oxidative stress or functional changes to their weapons. Our findings suggest that these powerful predators will not be hindered under future ocean conditions.

Rawat, R, Deheyn DD.  2016.  Evidence that ferritin is associated with light production in the mucus of the marine worm Chaetopterus. Scientific Reports. 6   10.1038/srep36854   AbstractWebsite

The blue glow of the mucus from Chaetopterus involves a photoprotein, iron and flavins. Identity and respective role of these components remain, however, largely unresolved today, likely because of viscosity issues and inhibition of this system by oxidizers conventionally used to track bioluminescence activity. Here, we used gentle centrifugation to obtain a mucus supernatant showing no inhibition to oxidizers, allowing for further analysis. We applied conventional chromatographic techniques to isolate major proteins associated with light emission. Luminescence ability of elutriate fractions was tested with hydrogen peroxide to track photoprotein and/or protein-bound chromophore. Fractions producing light contained few major proteins, one with similarity to ferritin. Addition to the mucus of elements with inhibitory/potentiary effect on ferritin ferroxidase activity induced corresponding changes in light production, emphasizing the possible role of ferritin in the worm bioluminescence. DNA of the protein was cloned, sequenced, and expressed, confirming its identity to a Chaetopterus Ferritin (ChF). Both ferric and ferrous iron were found in the mucus, indicating the occurrence of both oxidase and reductase activity. Biochemical analysis showed ChF has strong ferroxidase activity, which could be a source of biological iron and catalytic energy for the worm bioluminescence when coupled to a reduction process with flavins.

Holzinger, A, Allen MC, Deheyn DD.  2016.  Hyperspectral imaging of snow algae and green algae from aeroterrestrial habitats. Journal of Photochemistry and Photobiology B-Biology. 162:412-420.   10.1016/j.jphotobiol.2016.07.001   AbstractWebsite

Snow algae and green algae living in aeroterrestrial habitats are ideal objects to study adaptation to high light irradiation. Here, we used a detailed description of the spectral properties as a proxy for photo-acclimation/protection in snow algae (Chlamydomonas nivalis, Chlainomonas sp. and Chloromonas sp.) and charophyte green algae (Zygnema sp., Zygogonium ericetorum and Klebsormidium crenulatum). The hyperspectral microscopic mapping and imaging technique allowed us to acquire total absorption spectra of these microalgae in the waveband of 400-900 nm. Particularly in Chlamydomonas nivalis and Chlainomonas sp., a high absorbance between 400550 nm was observed, due to naturally occurring secondary carotenoids; in Chloromonas sp. and in the charopyhte algae this high absorbance was missing, the latter being close relatives to land plants. To investigate if cellular water loss has an influence on the spectral properties, the cells were plasmolysed in sorbitol or desiccated at ambient air. While in snow algae, these treatments did hardly change the spectral properties, in the charopyhte algae the condensation of the cytoplasm and plastids increased the absorbance in the lower waveband of 400-500 nm. These changes might be ecologically relevant and photoprotective, as aeroterrestrial algae are naturally exposed to occasional water limitation, leading to desiccation, which are conditions usually occurring together with higher irradiation. (C) 2016 The Authors. Published by Elsevier B.V.

Yue, JX, Holland ND, Holland LZ, Deheyn DD.  2016.  The evolution of genes encoding for green fluorescent proteins: insights from cephalochordates (amphioxus). Scientific Reports. 6   10.1038/srep28350   AbstractWebsite

Green Fluorescent Protein (GFP) was originally found in cnidarians, and later in copepods and cephalochordates (amphioxus) (Branchiostoma spp). Here, we looked for GFP-encoding genes in Asymmetron, an early-diverged cephalochordate lineage, and found two such genes closely related to some of the Branchiostoma GFPs. Dim fluorescence was found throughout the body in adults of Asymmetron lucayanum, and, as in Branchiostoma floridae, was especially intense in the ripe ovaries. Spectra of the fluorescence were similar between Asymmetron and Branchiostoma. Lineage-specific expansion of GFP-encoding genes in the genus Branchiostoma was observed, largely driven by tandem duplications. Despite such expansion, purifying selection has strongly shaped the evolution of GFP-encoding genes in cephalochordates, with apparent relaxation for highly duplicated clades. All cephalochordate GFP-encoding genes are quite different from those of copepods and cnidarians. Thus, the ancestral cephalochordates probably had GFP, but since GFP appears to be lacking in more early-diverged deuterostomes (echinoderms, hemichordates), it is uncertain whether the ancestral cephalochordates (i.e. the common ancestor of Asymmetron and Branchiostoma) acquired GFP by horizontal gene transfer (HGT) from copepods or cnidarians or inherited it from the common ancestor of copepods and deuterostomes, i.e. the ancestral bilaterians.

Gruber, DF, Loew ER, Deheyn DD, Akkaynak D, Gaffney JP, Smith WL, Davis MP, Stern JH, Pieribone VA, Sparks JS.  2016.  Biofluorescence in catsharks (Scyliorhinidae): Fundamental description and relevance for elasmobranch visual ecology. Scientific Reports. 6   10.1038/srep24751   AbstractWebsite

Biofluorescence has recently been found to be widespread in marine fishes, including sharks. Catsharks, such as the Swell Shark (Cephaloscyllium ventriosum) from the eastern Pacific and the Chain Catshark (Scyliorhinus retifer) from the western Atlantic, are known to exhibit bright green fluorescence. We examined the spectral sensitivity and visual characteristics of these reclusive sharks, while also considering the fluorescent properties of their skin. Spectral absorbance of the photoreceptor cells in these sharks revealed the presence of a single visual pigment in each species. Cephaloscyllium ventriosum exhibited a maximum absorbance of 484 +/- 3 nm and an absorbance range at half maximum (lambda(1/2max)) of 440-540 nm, whereas for S. retifer maximum absorbance was 488 +/- 3 nm with the same absorbance range. Using the photoreceptor properties derived here, a "shark eye" camera was designed and developed that yielded contrast information on areas where fluorescence is anatomically distributed on the shark, as seen from other sharks' eyes of these two species. Phylogenetic investigations indicate that biofluorescence has evolved at least three times in cartilaginous fishes. The repeated evolution of biofluorescence in elasmobranchs, coupled with a visual adaptation to detect it; and evidence that biofluorescence creates greater luminosity contrast with the surrounding background, highlights the potential importance of biofluorescence in elasmobranch behavior and biology.

Lin, HS, Allen MC, Wu J, deGlee BM, Shin D, Cai Y, Sandhage KH, Deheyn DD, Meredith JC.  2015.  Bioenabled core/shell microparticles with tailored multimodal adhesion and optical reflectivity. Chemistry of Materials. 27:7321-7330.   10.1021/acs.chemmater.5b02782   AbstractWebsite

Nature provides remarkable examples of mass-produced microscale particles with structures and chemistries optimized by evolution for particular functions. Synthetic chemical tailoring of such sustainable biogenic particles may be used to generate new multifunctional materials. Herein, we report a facile method for the development of bioenabled core/shell microparticles consisting of surface-modified ragweed pollen with a magnetic core, for which both multimodal adhesion and optical reflectivity can be tailored. Adhesion of the magnetic-core pollen can be tuned, relative to native pollen, through the combination of tailorable short-range interactions (over similar to 5 nm, via van der Waals forces and hydrogen bonding), an intermediate-range (over several mu m) capillary force, and long-range (over similar to 1 mm) magnetic attraction. The magnetic force could be controlled by the amount of iron oxide loaded within the core of the pollen particle, while the short-range interactions and capillary force can be tuned by coating with polystyrene nanoparticles and/or a layer of viscous pollenkitt on the exine shell surface. Such coatings were also used to tailor the optical reflectance of the magnetic pollen particles; that is, the light-reflectance intensity was enhanced by coating with pollenkitt and significantly reduced by coating with polystyrene nanoparticles. This approach for generating multifunctional core/shell microparticles with tailorable adhesion and optical reflectivity may be extended to other pollen or biological particles or to synthetic biomimetic particles. Such independent control of the core and shell chemistries enabled by this approach also allows for the generation of microparticles with a variety of combination in functions tailorable to other properties.

Taylor, JRA, Gilleard JM, Allen MC, Deheyn DD.  2015.  Effects of CO2-induced pH reduction on the exoskeleton structure and biophotonic properties of the shrimp Lysmata californica. Scientific Reports. 5   10.1038/srep10608   AbstractWebsite

The anticipated effects of CO2-induced ocean acidification on marine calcifiers are generally negative, and include dissolution of calcified elements and reduced calcification rates. Such negative effects are not typical of crustaceans for which comparatively little ocean acidification research has been conducted. Crustaceans, however, depend on their calcified exoskeleton for many critical functions. Here, we conducted a short-term study on a common caridean shrimp, Lysmata californica, to determine the effect of CO2-driven reduction in seawater pH on exoskeleton growth, structure, and mineralization and animal cryptic coloration. Shrimp exposed to ambient (7.99 +/- 0.04) and reduced pH (7.53 +/- 0.06) for 21 days showed no differences in exoskeleton growth (percent increase in carapace length), but the calcium weight percent of their cuticle increased significantly in reduced pH conditions, resulting in a greater Ca:Mg ratio. Cuticle thickness did not change, indicating an increase in the mineral to matrix ratio, which may have mechanical consequences for exoskeleton function. Furthermore, there was a 5-fold decrease in animal transparency, but no change in overall shrimp coloration (red). These results suggest that even short-term exposure to CO2-induced pH reduction can significantly affect exoskeleton mineralization and shrimp biophotonics, with potential impacts on crypsis, physical defense, and predator avoidance.

Yates, KK, Turley C, Hopkinson BM, Todgham AE, Cross JN, Greening H, Williamson P, Van Hooidonk R, Deheyn DD, Johnson Z.  2015.  Transdisciplinary science: A path to understanding the interactions among ocean acidification, ecosystem, and society. Oceanography. 28:212-225.   10.5670/oceanog.2015.43   AbstractWebsite

The global nature of ocean acidification (OA) transcends habitats, ecosystems, regions, and science disciplines. The scientific community recognizes that the biggest challenge in 'improving understanding of how changing OA conditions affect ecosystems, and associated consequences for human society, requires integration of experimental, observational, and modeling approaches from many disciplines over a wide range of temporal and spatial scales. Such transdisciplinary science is the next step in providing relevant, meaningful results and optimal guidance to policymakers and coastal managers. We discuss the challenges associated with integrating ocean acidification science across funding agencies, institutions, disciplines, topical areas, and regions, and the value of unifying science objectives and activities to deliver-insights into local, regional, and global scale impacts. We identify guiding principles and strategies for developing transdisciplinary research in the ocean acidification science community.

Xiao, M, Li YW, Allen MC, Deheyn DD, Yue XJ, Zhao JZ, Gianneschi NC, Shawkey MD, Dhinojwala A.  2015.  Bio-inspired structural colors produced via self-assembly of synthetic melanin nanoparticles. Acs Nano. 9:5454-5460.   10.1021/acsnano.5b01298   AbstractWebsite

Structural colors arising from interactions of light with submicron scale periodic structures have been found in many species across all taxa, serving multiple biological functions including sexual signaling, camouflage, and aposematism. Directly inspired by the extensive use of self-assembled melanosomes to produce colors in avian feathers, we set out to synthesize and assemble polydopamine-based synthetic melanin nanoparticles in an effort to fabricate colored films. We have quantitatively demonstrated that synthetic melanin nanoparticles have a high refractive index and broad absorption spanning across the UV-visible range, similar to natural melanins. Utilizing a thin-film interference model, we demonstrated the coloration mechanism of deposited films and showed that the unique optical properties of synthetic melanin nanoparticles provide advantages for structural colors over other polymeric nanoparticles (i.e., polystyrene colloidal particles).

Shah, DU, Vollrath F, Stires J, Deheyn DD.  2015.  The biocomposite tube of a chaetopterid marine worm constructed with highly-controlled orientation of nanofilaments. Materials Science & Engineering C-Materials for Biological Applications. 48:408-415.   10.1016/j.msec.2014.12.015   AbstractWebsite

The ultrastructure of the self-constructed tube housing of the bioluminescent marine worm, Chaetopterus sp. reveals that the bio-nanocomposite tube comprises of multiple non-woven plies of multi-axially oriented organic nanofilaments (empty set 50-1100 nm) cemented together by an unstructured organic matrix binder. The thin-walled, impermeable tubes are bin-inspirational for conventional pipe technology. Orientation distribution analyses revealed that the dominant orientation angles of nanofilaments in the tube were 0 degrees, +/- 45 degrees and +/- 65 degrees, which correlate well with optimal winding angles for 'man-made' fibre reinforced composite pipes subjected to specific loading conditions. Such a use of high aspect ratio nanofilaments in multi-axial laminates would impart toughness and flexibility to the tube structure, and facilitate rapid tube growth. While the tube production mechanism is not entirely known at this stage, our time-lapse studies show that, contrary to generic assumptions in literature, the worm actively, rapidly and sporadically produces and expands the tube. (C) 2014 Elsevier B.V. All rights reserved.

Zhang, Y, Allen MC, Zhao RY, Deheyn DD, Behrens SH, Meredith JC.  2015.  Capillary foams: Stabilization and functionalization of porous liquids and solids. Langmuir. 31:2669-2676.   10.1021/la504784h   AbstractWebsite

Liquid foams are two-phase systems in which a large volume of gas is dispersed as bubbles in a continuous liquid phase. These foams are ubiquitous in nature. In addition, they are found in industrial applications, such as pharmaceutical formulation, food processing, wastewater treatment, construction, and cosmetics. Recently, we reported a new type of foam material, capillary foam, which is stabilized by the synergistic action of particles and a small amount of an immiscible secondary liquid. In this study, we explore in more detail the foam preparation routes. To illustrate some of the potential applications, we create vividly colored wet and dried foams, which are difficult to prepare using traditional methods, and load-bearing porous solids. The combined action of particles and immiscible secondary fluid confers exceptional stability to capillary foams and many options for functionalization, suggesting a wide range of possible applications.

Shah, DU, Vollrath F, Porter D, Stires J, Deheyn DD.  2014.  Housing tubes from the marine worm Chaetopterus sp.: biomaterials with exceptionally broad thermomechanical properties. Journal of the Royal Society Interface. 11   10.1098/rsif.2014.0525   AbstractWebsite

The housing tube material of the marine worm Chaetopterus sp. exhibits thermal stability up to 250 degrees C, similar to other biological materials such as mulberry silkworm cocoons. Interestingly, however, dynamic mechanical thermal analysis conducted in both air and water elucidated the lack of a glass transition in the organic tube wall material. In fact, the viscoelastic properties of the anhydrous and undried tube were remarkably stable (i.e. constant and reversible) between -75 degrees C and 200 degrees C in air, and 5 degrees C and 75 degrees C in water, respectively. Moreover, it was found that hydration and associated-water plasticization were key to the rubber-like flexible properties of the tube; dehydration transformed the material behaviour to glass-like. The tube is made of bionanocomposite fibrils in highly oriented arrangement, which we argue favours the biomaterial to be highly crystalline or cross-linked, with extensive hydrogen and/or covalent bonds. Mechanical property characterization in the longitudinal and transverse directions ascertained that the tubes were not quasi-isotropic structures. In general, the higher stiffness and strength in the transverse direction implied that there were more nanofibrils orientated at +/- 45 degrees and +/- 65 degrees than at 0 degrees to the tube axis. The order of the mechanical properties of the soft-tough tubes was similar to synthetic rubber-like elastomers and even some viscid silks. The complex structure-property relations observed indicated that the worm has evolved to produce a tubular housing structure which can (i) function stably over a broad range of temperatures, (ii) endure mechanical stresses from specific planes/axes, and (iii) facilitate rapid growth or repair.

Bomati, EK, Haley JE, Noel JP, Deheyn DD.  2014.  Spectral and structural comparison between bright and dim green fluorescent proteins in Amphioxus. Scientific Reports. 4   10.1038/srep05469   AbstractWebsite

The cephalochordate Amphioxus naturally co-expresses fluorescent proteins (FPs) with different brightness, which thus offers the rare opportunity to identify FP molecular feature/s that are associated with greater/lower intensity of fluorescence. Here, we describe the spectral and structural characteristics of green FP (bfloGFPa1) with perfect (100%) quantum efficiency yielding to unprecedentedly-high brightness, and compare them to those of co-expressed bfloGFPc1 showing extremely-dim brightness due to low (0.1%) quantum efficiency. This direct comparison of structure-function relationship indicated that in the bright bfloGFPa1, a Tyrosine (Tyr159) promotes a ring flipping of a Tryptophan (Trp157) that in turn allows a cis-trans transformation of a Proline (Pro55). Consequently, the FP chromophore is pushed up, which comes with a slight tilt and increased stability. FPs are continuously engineered for improved biochemical and/or photonic properties, and this study provides new insight to the challenge of establishing a clear mechanistic understanding between chromophore structural environment and brightness level.