The Experts below are selected from a list of 1902 Experts worldwide ranked by ideXlab platform
Marianne Ellegaard - One of the best experts on this subject based on the ideXlab platform.
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The UV filtering potential of drop-casted layers of Frustules of three diatom species
'Springer Science and Business Media LLC', 2018Co-Authors: Torben Anker Lenau, Christian Maibohm, Emil Gundersen, Jacob J. K. Kirkensgaard, Jérôme Pinti, Marianne EllegaardAbstract:Abstract Diatoms are in focus as biological materials for a range of photonic applications. Many of these applications would require embedding a multitude of diatoms in a matrix (e.g. paint, crème or lacquer); however, most studies on the photonic and spectral properties of diatoms Frustules (silica walls) have been carried out on single cells. In this study, for the first time, we test the spectral properties of layers of Frustules of three diatom species (Coscinodiscus granii, Thalassiosira punctifera and Thalassiosira pseudonana), with special focus on transmission and reflectance in the UV range. The transmittance efficiency in the UV A and B range was: T. pseudonana (56–59%) >C. granii (53–54%) >T. punctifera (18–21%) for the rinsed Frustules. To investigate the underlying cause of these differences, we performed X-ray scattering analysis, measurement of layer thickness and microscopic determination of Frustule nanostructures. We further tested dried intact cells in the same experimental setup. Based on these data we discuss the relative importance of crystal structure properties, nanostructure and quantity of material on the spectral properties of diatom layers. Characterization of the UV protection performance of layers of diatom Frustules is of central relevance for their potential use as innovative bio-based UV filters
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long term cultivation of the diatom coscinodiscus granii at different light spectra effects on Frustule morphology
Journal of Applied Phycology, 2017Co-Authors: Nina Lundholm, Marianne EllegaardAbstract:The effect on diatom Frustule morphology of long-term cultivation at mono-spectral light (six wavelengths combined with two light intensities) was investigated. The results showed that the size of Coscinodiscus granii Frustules and the foramen size increased after 10-month cultivation for all light treatments, compared to results after short-term cultivation. The main difference between the light intensities was in the foramen density and similar to the short-term treatment, the lowest density was found at high-intensity red light. Thus, the mean foramen density and foramen diameter at red light 300 μmol photons m−2 s−1 and white light 100 μmol photons m−2 s−1 were statistically similar for short- and long-term tests. The foramen density was significantly reduced at all colored wavelengths at 100 μmol photons m−2 s−1, and blue and white light at 300 μmol photons m−2 s−1 after long-term compared to short-term cultivation. After both short- and long-term experiments, the foramen diameter showed a general trend of higher light intensity resulting in smaller foramen diameter, except for Y light. This study shows that C. granii can be maintained at mono-spectral light over long time periods and indicates that the most important morphological differences are maintained with the range of variability in some of these parameters being more constrained compared to short-term cultivation. This has important implications for mass cultivation of diatoms at different light conditions for applied purposes.
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the fascinating diatom Frustule can it play a role for attenuation of uv radiation
Journal of Applied Phycology, 2016Co-Authors: Marianne Ellegaard, Torben Anker Lenau, Nina Lundholm, Christian Maibohm, Soren Michael Mork Friis, Karsten Rottwitt, Yanyan SuAbstract:Diatoms are ubiquitous organisms in aquatic environments and are estimated to be responsible for 20–25 % of the total global primary production. A unique feature of diatoms is the silica wall, called the Frustule. The Frustule is characterized by species-specific intricate nanopatterning in the same size range as wavelengths of visible and ultraviolet (UV) light. This has prompted research into the possible role of the Frustule in mediating light for the diatoms’ photosynthesis as well as into possible photonic applications of the diatom Frustule. One of the possible biological roles, as well as area of potential application, is UV protection. In this review, we explore the possible adaptive value of the silica Frustule with focus on research on the effect of UV radiation on diatoms. We also explore the possible effect of the Frustules on UV radiation, from a theoretical, biological, and applied perspective, including recent experimental data on UV transmission of diatom Frustules.
Olav Vadstein - One of the best experts on this subject based on the ideXlab platform.
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Dynamic responses to silicon in Thalasiossira pseudonana - Identification, characterisation and classification of signature genes and their corresponding protein motifs
Scientific Reports, 2017Co-Authors: Tore Brembu, Matilde Skogen Chauton, Per Winge, Atle M. Bones, Olav VadsteinAbstract:The diatom cell wall, or Frustule, is a highly complex, three-dimensional structure consisting of nanopatterned silica as well as proteins and other organic components. While some key components have been identified, knowledge on Frustule biosynthesis is still fragmented. The model diatom Thalassiosira pseudonana was subjected to silicon (Si) shift-up and shift-down situations. Cellular and molecular signatures, dynamic changes and co-regulated clusters representing the hallmarks of cellular and molecular responses to changing Si availabilities were characterised. Ten new proteins with silaffin-like motifs, two kinases and a novel family of putatively Frustule-associated transmembrane proteins induced by Si shift-up with a possible role in Frustule biosynthesis were identified. A separate cluster analysis performed on all significantly regulated silaffin-like proteins (SFLPs), as well as silaffin-like motifs, resulted in the classification of silaffins, cingulins and SFLPs into distinct clusters. A majority of the genes in the Si-responsive clusters are highly divergent, but positive selection does not seem to be the driver behind this variability. This study provides a high-resolution map over transcriptional responses to changes in Si availability in T. pseudonana . Hallmark Si-responsive genes are identified, characteristic motifs and domains are classified, and taxonomic and evolutionary implications outlined and discussed.
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Titanium uptake and incorporation into silica nanostructures by the diatom Pinnularia sp. (Bacillariophyceae)
Journal of applied phycology, 2014Co-Authors: Matilde Skogen Chauton, Lotte M. B. Skolem, Lasse Mork Olsen, Per Erik Vullum, John C. Walmsley, Olav VadsteinAbstract:Diatoms are an ecologically successful group within the phytoplankton, and their special feature is a biofabricated silica cell encasement called a Frustule. These Frustules attract interest in material technology, and one potential application is to use them in solar cell technology. The silica Frustule with its nanoscaled pattern is interesting per se, but the utility is enhanced if we succeed in incorporating other elements. Titanium is an interesting element because its oxide is a semi-conductor with a high band gap. However, doping with relevant elements through bioincorporation is challenging, and it is necessary to understand the biology involved in element uptake and incorporation. Here we present data on bioincorporation of Ti into the silica Frustules of the pennate diatom Pinnularia sp. (Ehrenberg) and show that the distribution of the incorporated Ti is inhomogeneous both between and within valves. More than a tenfold increase of Ti in newly synthesised valves was achieved, and increased Ti around the pores was confirmed by both EDS and EELS analyses. HAADF STEM spectroscopy revealed a grainy surface with amorphous silica particles of 4 to 5 nm in size. These observations are explained by what is known from the physico-chemical processes involved in biosilification and Frustule formation, looking into it from a biological point of view.
Richard Wetherbee - One of the best experts on this subject based on the ideXlab platform.
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nanostructure of the diatom Frustule as revealed by atomic force and scanning electron microscopy
Journal of Phycology, 2001Co-Authors: Simon Crawford, Michael J Higgins, Paul Mulvaney, Richard WetherbeeAbstract:The cell wall (Frustule) of the freshwater diatom Pinnularia viridis (Nitzsch) Ehrenberg is composed of an assembly of highly silicified components and associated organic layers. We used atomic force microscopy (AFM) to investigate the nanostructure and relationship between the outermost surface organics and the siliceous Frustule components of live diatoms under natural hydrated conditions. Contact mode AFM imaging revealed that the walls were coated in a thick mucilaginous material that was interrupted only in the vicinity of the raphe fissure. Analysis of this mucilage by force mode AFM demonstrated it to be a nonadhesive, soft, and compressible material. Application of greater force to the sample during repeated scanning enabled the mucilage to be swept from the hard underlying siliceous components and piled into columns on either side of the scan area by the scanning action of the tip. The mucilage columns remained intact for several hours without dissolving or settling back onto the cleaned valve surface, thereby revealing a cohesiveness that suggested a degree of cross-linking. The hard silicified surfaces of the diatom Frustule appeared to be relatively smooth when living cells were imaged by AFM or when field-emission SEM was used to image chemically cleaned walls. AFM analysis of P. viridis Frustules cleaved in cross-section revealed the nanostructure of the valve silica to be composed of a conglomerate of packed silica spheres that were 44.8 ± 0.7 nm in diameter. The silica spheres that comprised the girdle band biosilica were 40.3 ± 0.8 nm in diameter. Analysis of another heavily silicified diatom, Hantzschia amphioxys (Ehrenberg) Grunow, showed that the valve biosilica was composed of packed silica spheres that were 37.1 ± 1.4 nm and that silica particles from the girdle bands were 38.1 ± 0.5 nm. These results showed little variation in the size range of the silica particles within a particular Frustule component (valve or girdle band), but there may be differences in particle size between these components within a diatom Frustule and significant differences are found between species.
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pleuralins are involved in theca differentiation in the diatom cylindrotheca fusiformis
Protist, 2000Co-Authors: Nils Kroger, Richard WetherbeeAbstract:Diatom cells are encased within a silica-based cell wall (Frustule) that serves as armour-like protection for the enclosed protoplast. Maintaining the integrity of the Frustule requires a precise coupling between the biogenesis of new Frustule components and the cell cycle. Thus far, the molecular mechanisms by which this coupling is achieved are unknown. This study demonstrates that pleuralins (formerly HEPs), a previously characterized family of diatom cell wall proteins, are involved in cell cycle-dependent Frustule development. The Frustule is made up of two, overlapping half-shells termed the epitheca and hypotheca. Both thecae are morphologically identical, yet immunolocalisation with anti-pleuralin antibodies demonstrates that their protein composition is clearly different. During interphase, pleuralins are associated only with the epitheca, where they are confined to the inner surface of the terminal elements (pleural bands) in the region of overlap with the hypotheca. At cell division, pleuralins also become associated with the newly formed pleural bands of the hypotheca. Remarkably, this process is concomitant with the functional conversion of the parental hypotheca into the epitheca of one of the progeny cells. These results indicate that developmentally controlled association of pleuralins with the Frustule is involved in hypotheca-epitheca differentiation, which is a crucial process to ensure proper Frustule development.
Mario De Stefano - One of the best experts on this subject based on the ideXlab platform.
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UV-shielding and wavelength conversion by centric diatom nanopatterned Frustules
Scientific Reports, 2018Co-Authors: Edoardo De Tommasi, Stefano Managò, Ilaria Rea, Principia Dardano, Roberta Congestri, Anna Chiara De Luca, Mario De StefanoAbstract:Diatoms can represent the major component of phytoplankton and contribute massively to global primary production in the oceans. Over tens of millions of years they developed an intricate porous silica shell, the Frustule, which ensures mechanical protection, sorting of nutrients from harmful agents, and optimization of light harvesting. Several groups of microalgae evolved different strategies of protection towards ultraviolet radiation (UVR), which is harmful for all living organisms mainly through the formation of dimeric photoproducts between adjacent pyrimidines in DNA. Even in presence of low concentrations of UV-absorbing compounds, several diatoms exhibit significant UVR tolerance. We here investigated the mechanisms involved in UVR screening by diatom silica investments focusing on single Frustules of a planktonic centric diatom, Coscinodiscus wailesii, analyzing absorption by the silica matrix, diffraction by Frustule ultrastructure and also UV conversion into photosynthetically active radiation exerted by nanostructured silica photoluminescence. We identified the defects and organic residuals incorporated in Frustule silica matrix which mainly contribute to absorption; simulated and measured the spatial distribution of UVR transmitted by a single valve, finding that it is confined far away from the diatom valve itself; furthermore, we showed how UV-to-blue radiation conversion (which is particularly significant for photosynthetic productivity) is more efficient than other emission transitions in the visible spectral range.
Gregory L Rorrer - One of the best experts on this subject based on the ideXlab platform.
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near infrared selective and angle independent backscattering from magnetite nanoparticle decorated diatom Frustules
ACS Photonics, 2014Co-Authors: Bin Jiang, Xiulun Yang, Micah Eastman, Yuming Liu, Linhui Wang, Jeremy Campbell, Lester Lampert, Ruikang K Wang, Gregory L Rorrer, Jun JiaoAbstract:Periodic heterogeneous structures exhibit color with brilliance through constructive interference of electromagnetic waves in accordance with Bragg’s law. However, the wavelength of diffracted light is strictly angle-dependent, and such periodic structures generate only iridescent color. Here we report that periodically porous, microellipsoidal shells of diatom Pinnularia sp. wavelength-selectively backscatter light at arbitrary incidence. The biosilica Frustules could be approximated as many polygonal faces of two-dimensional photonic crystal slabs. Furthermore, surface decoration of the Frustule with magnetite nanoparticles produced photonic band gaps in the near-infrared. Magnetite nanoparticle-decorated Frustules behave as angle-independent near-infrared reflectors and near-infrared contrast agents in optical coherence tomography.
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metabolic insertion of nanostructured tio2 into the patterned biosilica of the diatom pinnularia sp by a two stage bioreactor cultivation process
ACS Nano, 2008Co-Authors: Clayton Jeffryes, Jun Jiao, Timothy Gutu, Gregory L RorrerAbstract:Diatoms are single-celled algae that make silica shells or Frustules with intricate nanoscale features imbedded within periodic two-dimensional pore arrays. A two-stage photobioreactor cultivation process was used to metabolically insert titanium into the patterned biosilica of the diatom Pinnularia sp. In Stage I, diatom cells were grown up on dissolved silicon until silicon starvation was achieved. In Stage II, soluble titanium and silicon were continuously fed to the silicon-starved cell suspension (similar to 4 x 10(5) cells/mL) for 10 h. The feeding rate of titanium (0.85-7.3 mu mol Ti L-1 h(-1)) was designed to circumvent the precipitation of titanate in the liquid medium, and feeding rate of silicon (48 mu mol Si L-1 h(-1)) was designed to sustain one cell division. The addition of titanium to the culture had no detrimental effects on cell growth and preserved the Frustule morphology. Cofeeding of Ti and Si was required for complete intracellular uptake of Ti. The maximum bulk composition of titanium in the Frustule biosilica was 2.3 g of Ti/100 g of SiO2. Intact biosilica Frustules were isolated by treatment of diatom cells with SDS/EDTA and then analyzed by TEM and STEM-EDS. Titanium was preferentially deposited as a nanophase lining the base of each Frustule pore, with estimated local TiO2 content of nearly 80 wt %. Thermal annealing in air at 720 degrees C converted the biogenic titanate to anatase TiO2 with an average crystal size of 32 nm. This is the first reported study of using a living organism to controllably fabricate semiconductor TiO2 nanostructures by a bottom-up self-assembly process.
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two stage photobioreactor process for the metabolic insertion of nanostructured germanium into the silica microstructure of the diatom pinnularia sp
Materials Science and Engineering: C, 2008Co-Authors: Clayton Jeffryes, Jun Jiao, Timothy Gutu, Gregory L RorrerAbstract:There is significant interest in imbedding nanoscale germanium (Ge) into dielectric silica for optoelectronic applications. In this study, a bioreactor process was developed to metabolically insert nanostructured Ge into a patterned silica matrix of the diatom Pinnularia sp. at levels ranging from 0.24 to 0.97 wt.% Ge. In Stage I, the diatom cell culture was grown up to silicon starvation. In Stage II, soluble silicon and germanium were co-fed to the silicon-starved culture to promote one cell division during Ge uptake. In Stage II, soluble Si and Ge were transported into the silicon-starved diatom cell by a surge uptake process, and Ge uptake preceded its incorporation into the Frustule. STEM-EDS line scans of the Frustule in the newly-divided cells revealed that the Ge was uniformly incorporated into the biosilica. The overall shape of the new Frustule was intact, but Si-Ge oxides filled the Frustule areolae and altered their nanoscale pore size and geometry. Ge-rich pockets imbedded within the silica Frustule and Ge-rich nanoparticles littering the Frustule surface were also found. These results suggest that a two-stage diatom cultivation process can biologically fabricate and self-assemble new types of Ge-Si nanocomposite hierarchical materials that possess intricate submicron features. (C) 2007 Elsevier B.V. All rights reserved.
