Core-shell nanospheres behind the blue eyes of the bay scallop Argopecten irradians.

The bay scallop Argopecten irradians (Mollusca: Bivalvia) has dozens of iridescent blue eyes that focus light using mirror-based optics. Here, we test the hypothesis that these eyes appear blue because of photonic nanostructures that preferentially scatter short-wavelength light. Using transmission electron microscopy, we found that the epithelial cells covering the eyes of A. irradians have three distinct layers: an outer layer of microvilli, a middle layer of random close-packed nanospheres and an inner layer of pigment granules. The nanospheres are approximately 180 nm in diameter and consist of electron-dense cores approximately 140 nm in diameter surrounded by less electron-dense shells 20 nm thick. They are packed at a volume density of approximately 60% and energy-dispersive X-ray spectroscopy indicates that they are not mineralized. Optical modelling revealed that the nanospheres are an ideal size for producing angle-weighted scattering that is bright and blue. A comparative perspective supports our hypothesis: epithelial cells from the black eyes of the sea scallop Placopecten magellanicus have an outer layer of microvilli and an inner layer of pigment granules but lack a layer of nanospheres between them. We speculate that light-scattering nanospheres help to prevent UV wavelengths from damaging the internal structures of the eyes of A. irradians and other blue-eyed scallops.

A highly efficient TiO2@ZnO n-p-n heterojunction nanorod photocatalyst.

Shell@core-nanostructured TiO(2)@ZnO n-p-n heterojunction nanorods with diameter of 30 nm were successfully fabricated via a hydrothermal method. The photodegradation rate of the TiO(2)@ZnO n-p-n nanorods evaluated by photodegrading methyl orange has been demonstrated to increase three times compared to that of wurtzite hexagonal ZnO. Anatase TiO(2) and Ti(2)O(3) grow along ZnO crystal lattices, which forms p-type Zn(2+) doped Ti(2)O(3) in the interface of TiO(2)/ZnO and therefore numerous n-p-n heterojunctions owing to the substitution of Ti(3+) by Zn(2+). Under the drive of inner electric field, the photogenerated electrons are both injected to the conduction band of Zn(2+) doped Ti(2)O(3) from conduction bands of ZnO and TiO(2), which efficiently enhances the separation of photogenerated electron-hole pairs and accelerates the transport of charges. The results suggest that TiO(2)@ZnO n-p-n heterojunction nanorods are very promising for enhancing the photocatalytic activity of photocatalysts.

Uptake, distribution and toxicity of gold nanoparticles in tobacco (Nicotiana xanthi) seedlings.

Understanding plant interactions with nanoparticles is of increasing importance for assessing their toxicity and trophic transport. The primary objective of this study was to assess uptake, biodistribution and toxicity associated with exposure of tobacco plants (Nicotiana xanthi) to gold nanoparticles (AuNPs). We employed synchrotron-based X-ray microanalysis with X-ray absorption near-edge microspectroscopy and high resolution electron microscopy to localize AuNPs within plants. Results from these experiments reveal that AuNPs entered plants through the roots and moved into the vasculature. Aggregate bodies were also detected within root cell cytoplasm. Furthermore, AuNP uptake was size selective as 3.5 nm AuNP spheres were detected in plants but 18 nm AuNPs remained agglomerated on the root outer surfaces. Finally, leaf necrosis was observed after 14 days of exposure to 3.5 nm AuNPs. Overall, results of this work show the potential for AuNPs to enter plants through size-dependent mechanisms, translocate to cells and tissues and cause biotoxicity.

Visualizing cell extracellular matrix (ECM) deposited by cells cultured on aligned bacteriophage M13 thin films.

Topographical features ranging from micro- to nanometers can affect cell orientation and migratory pathways, which are important factors in tissue engineering and tumor migration. In our previous study, a convective assembly of bacteriophage M13 resulted in thin films which could be used to control the alignment of cells. However, several questions regarding its underlying reasons to dictate cell alignment remained unanswered. Here, we further study the nanometer topographical features generated by the bacteriophage M13 crystalline film, which results in the alignment of the cells and extracellular matrix (ECM) proteins. Sequential imaging analyses at micro- and nanoscale levels of aligned cells and fibrillar matrix proteins were documented using scanning electron microscopy and immunofluorescence microscopy. As a result, we observed baby hamster kidney cells with higher degree of alignment on the ordered M13 substrates than NIH-3T3 fibroblasts, a difference which could be attributed to the intrinsic nature of the cells' production of ECM proteins. The results from this study provide a crucial insight into the topographical features of a biological thin film, which can be utilized to control the orientation of cells and surrounding ECM proteins.

Effect of lead (Pb) on the systemic movement of RNA viruses in tobacco (Nicotiana tabacum var. Turkish).

Effect of various lead (Pb) concentrations on the systemic movement of RNA viruses was examined in tobacco plants. Prior to inoculation, plants were grown hydroponically for 6 days in Hoagland's solution supplemented with five concentrations of lead nitrate [Pb(NO(3))(2)]: 0.0 (control), 10, 15, 50, and 100 µM. Four different RNA viruses with different cell-to-cell movement mechanisms were used. Two weeks after inoculation lower and upper leaves of each treatment were harvested and examined for the presence of viral coat protein. In plants inoculated with Tobacco mosaic virus, Potato virus X, and Tobacco etch virus, TEM images and western blot assays confirmed the presence of viral coat proteins in the upper leaves of all lead treatments. However, in plants inoculated with Turnip vein-clearing virus (TVCV), no signs of viral particles were detected in the upper leaves of plants treated with 10 µM or 15 µM lead nitrate. In contrast, plants treated with high concentrations of lead nitrate (50 µM or 100 µM) showed viral particles in their upper leaves. In plants treated with 10 µM or 15 µM lead nitrate, callose accumulation was the same as in control plants. This suggests that non-toxic concentrations of lead nitrate may trigger the production of putative cellular factors in addition to callose that interfere with the TVCV systemic movement. In contrast, plants treated with 100 µM lead nitrate showed less callose as compared to control plants, facilitating the systemic movement of TVCV.

Synthesis and electron microscopic analysis of the self-assembly of polymer and ferritin core-shell structures.

Self-assembly of poly(4-vinylpyridine) (P4VP) and ferritin produced a spherical core-shell structure, which was analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In particular, for better understanding, the organization of such core-shell nanostructures, an optimal protocol for preparation of TEM thin sectioning of ferritin-P4VP composites, was developed. It entails fixing the ferritin-P4VP complex with 2.5% glutaraldehyde and infiltrating it with a mixture of acetone/resin while omitting the OsO(4) postfixation and ethanol dehydration steps of the conventional protocol. Using this method, a round-shaped thin section structure with unevenly distributed dark and white components was observed. The dark component from the thin section structure was determined to contain ferritin by energy-filtered TEM imaging and iron element mapping, whereas the white part was identified as P4VP by its energy dispersive X-ray spectroscopy (EDS) spectrum.

Controlled assembly of rodlike viruses with polymers.

A practical method to assemble rodlike tobacco mosaic virus and bateriophage M13 with polymers was developed, which afforded a 3D core-shell composite with morphological control.

Adsorption kinetics of Escherichia coli and Staphylococcus aureus on single-walled carbon nanotube aggregates.

Batch adsorption studies to determine adsorption kinetics of Escherichia coli (E.coli) K12 and Staphylococcus aureus (S.aureus) SH 1000 bacterial cells on single-walled carbon nanotube aggregates were performed at two different initial concentrations. The diffusivity of E. coli cells in single-walled carbon nanotube aggregates obtained was 6.54 x 10(-9) and 8.98 x 10(-9) cm(2)/s, whereas that of S. aureus was between 1.00 x 10(-7) and 1.66 x 10(-7) cm(2)/s respectively. In addition to batch adsorption studies, electron microscopy studies were also conducted. The results suggest that diffusion kinetics of bacterial cells is concentration dependent as well as bacteria dependent. Diffusivity of S. aureus is two orders of magnitude greater than E. coli cells. This proves to be beneficial from an adsorption perspective where it is desired to filter microorganisms (water pretreatment and wastewater post treatment) and from nanotube biosensor perspective where it is desired to simultaneously capture and detect biothreat agents in a shorter span of time.

Biochemical and molecular characterization of transgenic Lotus japonicus plants constitutively over-expressing a cytosolic glutamine synthetase gene.

Higher plants assimilate nitrogen in the form of ammonia through the concerted activity of glutamine synthetase (GS) and glutamate synthase (GOGAT). The GS enzyme is either located in the cytoplasm (GS1) or in the chloroplast (GS2). To understand how modulation of GS activity affects plant performance, Lotus japonicus L. plants were transformed with an alfalfa GS1 gene driven by the CaMV 35S promoter. The transformants showed increased GS activity and an increase in GS1 polypeptide level in all the organs tested. GS was analyzed by non-denaturing gel electrophoresis and ion-exchange chromatography. The results showed the presence of multiple GS isoenzymes in the different organs and the presence of a novel isoform in the transgenic plants. The distribution of GS in the different organs was analyzed by immunohistochemical localization. GS was localized in the mesophyll cells of the leaves and in the vasculature of the stem and roots of the transformants. Our results consistently showed higher soluble protein concentration, higher chlorophyll content and a higher biomass accumulation in the transgenic plants. The total amino acid content in the leaves and stems of the transgenic plants was 22-24% more than in the tissues of the non-transformed plants. The relative abundance of individual amino acid was similar except for aspartate/asparagine and proline, which were higher in the transformants.

TRANSPORT OF PROTEINS AND NUCLEIC ACIDS THROUGH PLASMODESMATA.

Despite a potentially key role in cell-to-cell communication, plant intercellular connections-the plasmodesmata-have long been a biological "black box." Little is known about their protein composition, regulatory mechanisms, or transport pathways. However, recent studies have shed some light on plasmodesmal function. These connections have been shown to actively traffic proteins and protein-nucleic acid complexes between plant cells. This review describes these transport processes-specifically, cell-to-cell movement of plant viruses as well as endogenous cellular proteins-and discusses their possible mechanism(s). For comparison and to provide a broader perspective on the plasmodesmal transport process, the current model for nuclear import, the only other known example of transport of large proteins and protein-nucleic acid complexes through a membrane pore, is summarized. Finally, the function of plasmodesmata as communication boundaries within plant tissue is discussed.