Publications by authors named "Dimitri D Deheyn"

54 Publications

Degradation of synthetic and wood-based cellulose fabrics in the marine environment: Comparative assessment of field, aquarium, and bioreactor experiments.

Sci Total Environ 2021 May 27;791:148060. Epub 2021 May 27.

Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093, USA. Electronic address:

As global production of textiles rapidly grows, there is urgency to understand the persistence of fabrics in the marine environment, particularly from the microfibers they shed during wearing and washing. Here, we show that fabrics containing polyester (one of the most common plastics) remained relatively intact (viz., with a limited biofilm) after >200 days in seawater off the Scripps Oceanography pier (La Jolla, CA), in contrast to wood-based cellulose fabrics that fell apart within 30 days. We also show similar results under experimental aquaria (in open circuit with the pier waters) as well as bioreactor settings (in close circuit, using microbial inoculum from the North Sea, off Belgium), using nonwoven fabrics and individual fibers, respectively. The fact that fibers released from synthetic textiles remain persistent and non-biodegradable despite their small (invisible) size, highlights concern for the growing industry that uses polyester from recycled plastics to make clothing.
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http://dx.doi.org/10.1016/j.scitotenv.2021.148060DOI Listing
May 2021

Unraveling the Structure and Function of Melanin through Synthesis.

J Am Chem Soc 2021 02 9;143(7):2622-2637. Epub 2021 Feb 9.

Department of Chemistry & Biochemistry, University of California, San Diego, La Jolla, California 92093, United States.

Melanin is ubiquitous in living organisms across different biological kingdoms of life, making it an important, natural biomaterial. Its presence in nature from microorganisms to higher animals and plants is attributed to the many functions of melanin, including pigmentation, radical scavenging, radiation protection, and thermal regulation. Generally, melanin is classified into five types-eumelanin, pheomelanin, neuromelanin, allomelanin, and pyomelanin-based on the various chemical precursors used in their biosynthesis. Despite its long history of study, the exact chemical makeup of melanin remains unclear, and it moreover has an inherent diversity and complexity of chemical structure, likely including many functions and properties that remain to be identified. Synthetic mimics have begun to play a broader role in unraveling structure and function relationships of natural melanins. In the past decade, polydopamine, which has served as the conventional form of synthetic eumelanin, has dominated the literature on melanin-based materials, while the synthetic analogues of other melanins have received far less attention. In this perspective, we will discuss the synthesis of melanin materials with a special focus beyond polydopamine. We will emphasize efforts to elucidate biosynthetic pathways and structural characterization approaches that can be harnessed to interrogate specific structure-function relationships, including electron paramagnetic resonance (EPR) and solid-state nuclear magnetic resonance (ssNMR) spectroscopy. We believe that this timely Perspective will introduce this class of biopolymer to the broader chemistry community, where we hope to stimulate new opportunities in novel, melanin-based poly-functional synthetic materials.
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http://dx.doi.org/10.1021/jacs.0c12322DOI Listing
February 2021

Human Health and Ocean Pollution.

Ann Glob Health 2020 12 3;86(1):151. Epub 2020 Dec 3.

Nigerian Institute for Medical Research, Lagos, NG.

Background: Pollution - unwanted waste released to air, water, and land by human activity - is the largest environmental cause of disease in the world today. It is responsible for an estimated nine million premature deaths per year, enormous economic losses, erosion of human capital, and degradation of ecosystems. Ocean pollution is an important, but insufficiently recognized and inadequately controlled component of global pollution. It poses serious threats to human health and well-being. The nature and magnitude of these impacts are only beginning to be understood.

Goals: (1) Broadly examine the known and potential impacts of ocean pollution on human health. (2) Inform policy makers, government leaders, international organizations, civil society, and the global public of these threats. (3) Propose priorities for interventions to control and prevent pollution of the seas and safeguard human health.

Methods: Topic-focused reviews that examine the effects of ocean pollution on human health, identify gaps in knowledge, project future trends, and offer evidence-based guidance for effective intervention.

Environmental Findings: Pollution of the oceans is widespread, worsening, and in most countries poorly controlled. It is a complex mixture of toxic metals, plastics, manufactured chemicals, petroleum, urban and industrial wastes, pesticides, fertilizers, pharmaceutical chemicals, agricultural runoff, and sewage. More than 80% arises from land-based sources. It reaches the oceans through rivers, runoff, atmospheric deposition and direct discharges. It is often heaviest near the coasts and most highly concentrated along the coasts of low- and middle-income countries. Plastic is a rapidly increasing and highly visible component of ocean pollution, and an estimated 10 million metric tons of plastic waste enter the seas each year. Mercury is the metal pollutant of greatest concern in the oceans; it is released from two main sources - coal combustion and small-scale gold mining. Global spread of industrialized agriculture with increasing use of chemical fertilizer leads to extension of Harmful Algal Blooms (HABs) to previously unaffected regions. Chemical pollutants are ubiquitous and contaminate seas and marine organisms from the high Arctic to the abyssal depths.

Ecosystem Findings: Ocean pollution has multiple negative impacts on marine ecosystems, and these impacts are exacerbated by global climate change. Petroleum-based pollutants reduce photosynthesis in marine microorganisms that generate oxygen. Increasing absorption of carbon dioxide into the seas causes ocean acidification, which destroys coral reefs, impairs shellfish development, dissolves calcium-containing microorganisms at the base of the marine food web, and increases the toxicity of some pollutants. Plastic pollution threatens marine mammals, fish, and seabirds and accumulates in large mid-ocean gyres. It breaks down into microplastic and nanoplastic particles containing multiple manufactured chemicals that can enter the tissues of marine organisms, including species consumed by humans. Industrial releases, runoff, and sewage increase frequency and severity of HABs, bacterial pollution, and anti-microbial resistance. Pollution and sea surface warming are triggering poleward migration of dangerous pathogens such as the species. Industrial discharges, pharmaceutical wastes, pesticides, and sewage contribute to global declines in fish stocks.

Human Health Findings: Methylmercury and PCBs are the ocean pollutants whose human health effects are best understood. Exposures of infants to these pollutants through maternal consumption of contaminated seafood can damage developing brains, reduce IQ and increase children's risks for autism, ADHD and learning disorders. Adult exposures to methylmercury increase risks for cardiovascular disease and dementia. Manufactured chemicals - phthalates, bisphenol A, flame retardants, and perfluorinated chemicals, many of them released into the seas from plastic waste - can disrupt endocrine signaling, reduce male fertility, damage the nervous system, and increase risk of cancer. HABs produce potent toxins that accumulate in fish and shellfish. When ingested, these toxins can cause severe neurological impairment and rapid death. HAB toxins can also become airborne and cause respiratory disease. Pathogenic marine bacteria cause gastrointestinal diseases and deep wound infections. With climate change and increasing pollution, risk is high that infections, including cholera, will increase in frequency and extend to new areas. All of the health impacts of ocean pollution fall disproportionately on vulnerable populations in the Global South - environmental injustice on a planetary scale.

Conclusions: Ocean pollution is a global problem. It arises from multiple sources and crosses national boundaries. It is the consequence of reckless, shortsighted, and unsustainable exploitation of the earth's resources. It endangers marine ecosystems. It impedes the production of atmospheric oxygen. Its threats to human health are great and growing, but still incompletely understood. Its economic costs are only beginning to be counted.Ocean pollution can be prevented. Like all forms of pollution, ocean pollution can be controlled by deploying data-driven strategies based on law, policy, technology, and enforcement that target priority pollution sources. Many countries have used these tools to control air and water pollution and are now applying them to ocean pollution. Successes achieved to date demonstrate that broader control is feasible. Heavily polluted harbors have been cleaned, estuaries rejuvenated, and coral reefs restored.Prevention of ocean pollution creates many benefits. It boosts economies, increases tourism, helps restore fisheries, and improves human health and well-being. It advances the Sustainable Development Goals (SDG). These benefits will last for centuries.

Recommendations: World leaders who recognize the gravity of ocean pollution, acknowledge its growing dangers, engage civil society and the global public, and take bold, evidence-based action to stop pollution at source will be critical to preventing ocean pollution and safeguarding human health.Prevention of pollution from land-based sources is key. Eliminating coal combustion and banning all uses of mercury will reduce mercury pollution. Bans on single-use plastic and better management of plastic waste reduce plastic pollution. Bans on persistent organic pollutants (POPs) have reduced pollution by PCBs and DDT. Control of industrial discharges, treatment of sewage, and reduced applications of fertilizers have mitigated coastal pollution and are reducing frequency of HABs. National, regional and international marine pollution control programs that are adequately funded and backed by strong enforcement have been shown to be effective. Robust monitoring is essential to track progress.Further interventions that hold great promise include wide-scale transition to renewable fuels; transition to a circular economy that creates little waste and focuses on equity rather than on endless growth; embracing the principles of green chemistry; and building scientific capacity in all countries.Designation of Marine Protected Areas (MPAs) will safeguard critical ecosystems, protect vulnerable fish stocks, and enhance human health and well-being. Creation of MPAs is an important manifestation of national and international commitment to protecting the health of the seas.
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http://dx.doi.org/10.5334/aogh.2831DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7731724PMC
December 2020

Comparative Animal Mucomics: Inspiration for Functional Materials from Ubiquitous and Understudied Biopolymers.

ACS Biomater Sci Eng 2020 10 14;6(10):5377-5398. Epub 2020 Sep 14.

The PhD Program in Biochemistry, Graduate Center of the City University of New York, 365 Fifth Avenue, New York, New York 10016, United States.

The functions of secreted animal mucuses are remarkably diverse and include lubricants, wet adhesives, protective barriers, and mineralizing agents. Although present in all animals, many open questions related to the hierarchical architectures, material properties, and genetics of mucus remain. Here, we summarize what is known about secreted mucus structure, describe the work of research groups throughout the world who are investigating various animal mucuses, and relate how these studies are revealing new mucus properties and the relationships between mucus hierarchical structure and hydrogel function. Finally, we call for a more systematic approach to studying animal mucuses so that data sets can be compared, omics-style, to address unanswered questions in the emerging field of mucomics. One major result that we anticipate from these efforts is design rules for creating new materials that are inspired by the structures and functions of animal mucuses.
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http://dx.doi.org/10.1021/acsbiomaterials.0c00713DOI Listing
October 2020

In situ differentiation of iridophore crystallotypes underlies zebrafish stripe patterning.

Nat Commun 2020 12 15;11(1):6391. Epub 2020 Dec 15.

Department of Biology, University of Virginia, Charlottesville, VA, USA.

Skin color patterns are ubiquitous in nature, impact social behavior, predator avoidance, and protection from ultraviolet irradiation. A leading model system for vertebrate skin patterning is the zebrafish; its alternating blue stripes and yellow interstripes depend on light-reflecting cells called iridophores. It was suggested that the zebrafish's color pattern arises from a single type of iridophore migrating differentially to stripes and interstripes. However, here we find that iridophores do not migrate between stripes and interstripes but instead differentiate and proliferate in-place, based on their micro-environment. RNA-sequencing analysis further reveals that stripe and interstripe iridophores have different transcriptomic states, while cryogenic-scanning-electron-microscopy and micro-X-ray diffraction identify different crystal-arrays architectures, indicating that stripe and interstripe iridophores are different cell types. Based on these results, we present an alternative model of skin patterning in zebrafish in which distinct iridophore crystallotypes containing specialized, physiologically responsive, organelles arise in stripe and interstripe by in-situ differentiation.
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http://dx.doi.org/10.1038/s41467-020-20088-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7738553PMC
December 2020

Toward Bioinspired Wet Adhesives: Lessons from Assessing Surface Structures of the Suction Disc of Intertidal Clingfish.

ACS Appl Mater Interfaces 2020 Oct 24;12(40):45460-45475. Epub 2020 Sep 24.

Marine Biology Research Division, Scripps Institution of Oceanography, UC San Diego, 9500 Gilman Drive, La Jolla, California 92093, United States.

The clingfish attaches to rough surfaces with considerable strength using an intricate suction disc, which displays complex surface geometries from structures called papillae. However, the exact role of these structures in adhesion is poorly understood. To investigate the relationship between papillae geometry and adhesive performance, we developed an image processing tool that analyzed the surface and structural complexity of papillae, which we then used to model hydrodynamic adhesion. Our tool allowed for the automated analysis of thousands of papillae in specimens across a range of body sizes. The results led us to identify spatial trends in papillae across the complex geometry of the suction disc and to establish fundamental structure-function relationships used in hydrodynamic adhesion. We found that the surface area of papillae changed within a suction disc and with fish size, but that the aspect ratios and channel width between papillae did not. Using a mathematical model, we found that the surface structures can adhere considerably when subjected to disturbances of moderate to high velocities. We concluded that a predominant role of the papillae is to leverage hydrodynamic adhesion and wet friction to reinforce the seal of the suction disc. Overall, the trends in papillae characteristics provided insights into bioinspired designs of surface microstructures for future applications in which adhesion is necessary to attach to diverse surfaces (in terrestrial or aquatic environments), even when subjected to disturbance forces of randomized directionality.
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http://dx.doi.org/10.1021/acsami.0c10749DOI Listing
October 2020

Limitations on electromagnetic communication by vibrational resonances in biological systems.

Phys Rev E 2020 Jun;101(6-1):062401

Department of Electrical Engineering, University of California San Diego, San Diego, California 92161, USA.

Previous research in biology and physics speculates that high-frequency electromagnetic fields may be an unexplored method of cellular and subcellular communication. The predominant theory for generating electric fields in the cell is mechanical vibration of charged or polar biomolecules such as cell membranes or microtubules. The challenge to this theory is explaining how high-frequency vibrations would not be overdamped by surrounding biological media. As many of these suspected resonators are too large for atomistic molecular dynamics simulations, accurately modeling biological resonators remains an ongoing challenge. While many resonators have been studied and simulated, the general limitations on communication imposed by energy transfer arguments have not been considered. Starting with energy transfer expressions from coupled-mode theory, we derive expressions for the minimum quality factor (Q factor) required to sustain communication for both near- and far-field interactions. We compare previous simulation studies and our theory. We determine the flexing mode of microtubules as an identified resonance in the literature which meets our criteria. Our results suggest the major obstacle to meeting our criteria for effective electromagnetic communication is the trade-off between the Q factor and the plasma frequency: Resonators must be large enough to have a large Q factor, but small enough to resonate at frequencies greater than the plasma frequency.
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http://dx.doi.org/10.1103/PhysRevE.101.062401DOI Listing
June 2020

Bionic 3D printed corals.

Nat Commun 2020 04 9;11(1):1748. Epub 2020 Apr 9.

Bioinspired Photonics Group, Department of Chemistry, University of Cambridge, Cambridge, UK.

Corals have evolved as optimized photon augmentation systems, leading to space-efficient microalgal growth and outstanding photosynthetic quantum efficiencies. Light attenuation due to algal self-shading is a key limiting factor for the upscaling of microalgal cultivation. Coral-inspired light management systems could overcome this limitation and facilitate scalable bioenergy and bioproduct generation. Here, we develop 3D printed bionic corals capable of growing microalgae with high spatial cell densities of up to 10 cells mL. The hybrid photosynthetic biomaterials are produced with a 3D bioprinting platform which mimics morphological features of living coral tissue and the underlying skeleton with micron resolution, including their optical and mechanical properties. The programmable synthetic microenvironment thus allows for replicating both structural and functional traits of the coral-algal symbiosis. Our work defines a class of bionic materials that is capable of interacting with living organisms and can be exploited for applied coral reef research and photobioreactor design.
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http://dx.doi.org/10.1038/s41467-020-15486-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7145811PMC
April 2020

Iron redox pathway revealed in ferritin via electron transfer analysis.

Sci Rep 2020 03 4;10(1):4033. Epub 2020 Mar 4.

Department of Mechanical Engineering, University of California, San Diego, La Jolla, CA, 92093, USA.

Ferritin protein is involved in biological tissues in the storage and management of iron - an essential micro-nutrient in the majority of living systems. While there are extensive studies on iron-loaded ferritin, its functionality in iron delivery is not completely clear. Here, for the first time, differential pulse voltammetry (DPV) has been successfully adapted to address the challenge of resolving a cascade of fast and co-occurring redox steps in enzymatic systems such as ferritin. Using DPV, comparative analysis of ferritins from two evolutionary-distant organisms has allowed us to propose a stepwise resolution for the complex mix of concurrent redox steps that is inherent to ferritins and to fine-tune the structure-function relationship of each redox step. Indeed, the cyclic conversion between Fe and Fe as well as the different oxidative steps of the various ferroxidase centers already known in ferritins were successfully discriminated, bringing new evidence that both the 3-fold and 4-fold channels can be functional in ferritin.
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http://dx.doi.org/10.1038/s41598-020-60640-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7055317PMC
March 2020

Simulation of electric fields generated from microtubule vibrations.

Phys Rev E 2019 Aug;100(2-1):022410

Electrical Engineering Department, University of California, San Diego, California 92093, USA.

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 10nm from the surface of the microtubule, but interaction is not likely at greater distances.
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http://dx.doi.org/10.1103/PhysRevE.100.022410DOI Listing
August 2019

Reversible adhesion to rough surfaces both in and out of water, inspired by the clingfish suction disc.

Bioinspir Biomim 2019 10 25;14(6):066016. Epub 2019 Oct 25.

Department of Mechanical and Aerospace Engineering, University of California San Diego, 9500 Gilman Dr., La Jolla, CA 92093, United States of America.

Adhesion is difficult to achieve on rough surfaces both in air and underwater. In nature, the northern clingfish (Gobiesox maeandricus) has evolved the impressive ability to adhere onto substrates of various shapes and roughnesses, while subject to strong intertidal surges. The suction disc of the clingfish relies on suction and friction to achieve and maintain adhesion. Inspired by this mechanism of attachment, we designed an artificial suction disc and evaluated its adhesive stress on rough surfaces and non-planar geometries. The artificial suction disc achieved adhesion strengths of 10.1  ±  0.3 kPa in air on surfaces of moderate roughness (grain size, 68 µm), and 14.3  ±  1.5 kPa underwater on coarse surfaces (grain size, 269 µm). By comparison, a commercially available suction cup failed to exhibit any significant adhesion in both scenarios. The roughly 2 g heavy clingfish-inspired suction discs gripped concave surfaces with small radii of curvature (12.5 mm) and supported payloads up to 0.7 kg. We correlated the effect of key bioinspired features (i.e. slits, a soft outer layer, and body geometry) to adhesion performance using contact visualization techniques and finite element analysis (FEA). The suction discs were then tested on a remotely operated vehicle (ROV) to demonstrate their utility in the soft manipulation of fragile objects.
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http://dx.doi.org/10.1088/1748-3190/ab47d1DOI Listing
October 2019

Fate plasticity and reprogramming in genetically distinct populations of leucophores.

Proc Natl Acad Sci U S A 2019 06 28;116(24):11806-11811. Epub 2019 May 28.

Department of Biology, University of Virginia, Charlottesville, VA 22903;

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 fishes, including the zebrafish , 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.
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http://dx.doi.org/10.1073/pnas.1901021116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6575160PMC
June 2019

Acquisition of obligate mutualist symbionts during the larval stage is not beneficial for a coral host.

Mol Ecol 2019 01;28(1):141-155

Department of Biology, Pennsylvania State University, University Park, Pennsylvania.

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.
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http://dx.doi.org/10.1111/mec.14967DOI Listing
January 2019

Before platelets: the production of platelet-activating factor during growth and stress in a basal marine organism.

Proc Biol Sci 2018 08 15;285(1884). Epub 2018 Aug 15.

Department of Biology, San Diego State University, San Diego, CA 92182-4614, USA

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.
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http://dx.doi.org/10.1098/rspb.2018.1307DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6111180PMC
August 2018

Translucent soft robots driven by frameless fluid electrode dielectric elastomer actuators.

Sci Robot 2018 04;3(17)

Department of Mechanical and Aerospace Engineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.

Dielectric elastomer actuators (DEAs) are a promising enabling technology for a wide range of emerging applications, including robotics, artificial muscles, 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 electrode materials; (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.
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http://dx.doi.org/10.1126/scirobotics.aat1893DOI Listing
April 2018

Rainbow peacock spiders inspire miniature super-iridescent optics.

Nat Commun 2017 12 22;8(1):2278. Epub 2017 Dec 22.

Department of Biology and Integrated Bioscience Program, The University of Akron, Akron, OH, 44325, USA.

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 (~ 40 × 10 μm) 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.
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http://dx.doi.org/10.1038/s41467-017-02451-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5741626PMC
December 2017

Photobiology: How flowers get the blues to lure bees.

Authors:
Dimitri D Deheyn

Nature 2017 10 18;550(7677):467-468. Epub 2017 Oct 18.

Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093, USA.

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http://dx.doi.org/10.1038/nature24155DOI Listing
October 2017

Stress physiology and weapon integrity of intertidal mantis shrimp under future ocean conditions.

Sci Rep 2016 12 15;6:38637. Epub 2016 Dec 15.

Scripps Institution of Oceanography, Marine Biology Research Division, University of California at San Diego, La Jolla, CA 92093 USA.

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.
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http://dx.doi.org/10.1038/srep38637DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5156921PMC
December 2016

Evidence that ferritin is associated with light production in the mucus of the marine worm Chaetopterus.

Sci Rep 2016 11 10;6:36854. Epub 2016 Nov 10.

Scripps Institution of Oceanography, Marine Biology Research Division, University of California San Diego, 9500 Gillman Drive, La Jolla, CA 92093, USA.

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.
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http://dx.doi.org/10.1038/srep36854DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5103273PMC
November 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 2016 Dec 20;25(10):1720-1729. Epub 2016 Sep 20.

Marine Biology Research Division Scripps Institution of Oceanography, University of California, 9500 Gilman Drive, La Jolla, San Diego, CA, 92093-0202, USA.

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 μg/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 μg/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 μg/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.
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http://dx.doi.org/10.1007/s10646-016-1705-zDOI Listing
December 2016

Hyperspectral imaging of snow algae and green algae from aeroterrestrial habitats.

J Photochem Photobiol B 2016 Sep 5;162:412-420. Epub 2016 Jul 5.

Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0202, USA. Electronic address:

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 400-900nm. Particularly in Chlamydomonas nivalis and Chlainomonas sp., a high absorbance between 400-550nm 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 400-500nm. 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.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5061078PMC
http://dx.doi.org/10.1016/j.jphotobiol.2016.07.001DOI Listing
September 2016

The evolution of genes encoding for green fluorescent proteins: insights from cephalochordates (amphioxus).

Sci Rep 2016 06 17;6:28350. Epub 2016 Jun 17.

Marine Biology Research Division, Scripps Institution of Oceanography, UC San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.

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.
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http://dx.doi.org/10.1038/srep28350DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4911609PMC
June 2016

Biofluorescence in Catsharks (Scyliorhinidae): Fundamental Description and Relevance for Elasmobranch Visual Ecology.

Sci Rep 2016 04 25;6:24751. Epub 2016 Apr 25.

American Museum of Natural History, Sackler Institute for Comparative Genomics, New York, NY 10024, USA.

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 (λ1/2max) 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.
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http://dx.doi.org/10.1038/srep24751DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4843165PMC
April 2016

Blue reflectance in tarantulas is evolutionarily conserved despite nanostructural diversity.

Sci Adv 2015 Nov 27;1(10):e1500709. Epub 2015 Nov 27.

Department of Biology and Integrated Bioscience Program, The University of Akron, Akron, OH 44325-3908, USA.

Slight shifts in arrangement within biological photonic nanostructures can produce large color differences, and sexual selection often leads to high color diversity in clades with structural colors. We use phylogenetic reconstruction, electron microscopy, spectrophotometry, and optical modeling to show an opposing pattern of nanostructural diversification accompanied by unusual conservation of blue color in tarantulas (Araneae: Theraphosidae). In contrast to other clades, blue coloration in phylogenetically distant tarantulas peaks within a narrow 20-nm region around 450 nm. Both quasi-ordered and multilayer nanostructures found in different tarantulas produce this blue color. Thus, even within monophyletic lineages, tarantulas have evolved strikingly similar blue coloration through divergent mechanisms. The poor color perception and lack of conspicuous display during courtship of tarantulas argue that these colors are not sexually selected. Therefore, our data contrast with sexual selection that typically produces a diverse array of colors with a single structural mechanism by showing that natural selection on structural color in tarantulas resulted in convergence on similar color through diverse structural mechanisms.
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http://dx.doi.org/10.1126/sciadv.1500709DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4681340PMC
November 2015

Effects of CO2-induced pH reduction on the exoskeleton structure and biophotonic properties of the shrimp Lysmata californica.

Sci Rep 2015 Jun 1;5:10608. Epub 2015 Jun 1.

Scripps Institution of Oceanography, Marine Biology Research Division, University of California, San Diego.

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.
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http://dx.doi.org/10.1038/srep10608DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4450593PMC
June 2015

Bio-Inspired Structural Colors Produced via Self-Assembly of Synthetic Melanin Nanoparticles.

ACS Nano 2015 May 12;9(5):5454-60. Epub 2015 May 12.

†Department of Polymer Science, The University of Akron, Akron, Ohio 44325, United States.

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).
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http://dx.doi.org/10.1021/acsnano.5b01298DOI Listing
May 2015

Capillary foams: stabilization and functionalization of porous liquids and solids.

Langmuir 2015 Mar 26;31(9):2669-76. Epub 2015 Feb 26.

School of Chemical & Biomolecular Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332-0100, United States.

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.
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http://dx.doi.org/10.1021/la504784hDOI Listing
March 2015

The biocomposite tube of a chaetopterid marine worm constructed with highly-controlled orientation of nanofilaments.

Mater Sci Eng C Mater Biol Appl 2015 Mar 9;48:408-15. Epub 2014 Dec 9.

Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La California 92093-0202, USA. Electronic address:

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 (ø 50-1100nm) cemented together by an unstructured organic matrix binder. The thin-walled, impermeable tubes are bio-inspirational for conventional pipe technology. Orientation distribution analyses revealed that the dominant orientation angles of nanofilaments in the tube were 0°, ±45° and ±65°, 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.
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http://dx.doi.org/10.1016/j.msec.2014.12.015DOI Listing
March 2015

Housing tubes from the marine worm Chaetopterus sp.: biomaterials with exceptionally broad thermomechanical properties.

J R Soc Interface 2014 Sep;11(98):20140525

Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0202, USA

The housing tube material of the marine worm Chaetopterus sp. exhibits thermal stability up to 250°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°C and 200°C in air, and 5°C and 75°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° and ± 65° than at 0° 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.
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http://dx.doi.org/10.1098/rsif.2014.0525DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4233702PMC
September 2014

Spectral and structural comparison between bright and dim green fluorescent proteins in Amphioxus.

Sci Rep 2014 Jun 27;4:5469. Epub 2014 Jun 27.

Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92037 USA.

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.
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http://dx.doi.org/10.1038/srep05469DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4073121PMC
June 2014
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