Search

The prebiotic synthesis of ribonucleotides is likely to have been accompanied by the synthesis of noncanonical nucleotides including the threo-nucleotide building blocks of TNA. Here, we examine the ability of activated threo-nucleotides to participate in nonenzymatic template-directed polymerization. We find that primer extension by multiple sequential threo-nucleotide monomers is strongly disfavored relative to ribo-nucleotides. Kinetic, NMR and crystallographic studies suggest that this is due in part to the slow formation of the imidazolium-bridged TNA dinucleotide intermediate in primer extension, and in part because of the greater distance between the attacking RNA primer 3′-hydroxyl and the phosphate of the incoming threo-nucleotide intermediate. Even a single activated threo-nucleotide in the presence of an activated downstream RNA oligonucleotide is added to the primer 10-fold more slowly than an activated ribonucleotide. In contrast, a single activated threo-nucleotide at the end of an RNA primer or in an RNA template results in only a modest decrease in the rate of primer extension, consistent with the minor and local structural distortions revealed by crystal structures. Our results are consistent with a model in which heterogeneous primordial oligonucleotides would, through cycles of replication, have given rise to increasingly homogeneous RNA strands.

Monolith is an emerging technology applicable for separation, filtration, and chromatography due to its interconnected pore structure. However, the current templates used to form monolith pores are associated with poor heat dissipation, uneven pore size distribution, and relatively low mechanical strength during monolith scale-up. Templates made from polymeric microsphere particles were synthesized via a solvent evaporation technique using different types of polymer (polystyrene, polycaprolactone, polypropylene, polyethylene, and poly (vinyl-alcohol) at varied polymer (10–40 wt%) and surfactant (5–10%) concentrations. The resulting microsphere particles were tested as a monolith template for the formation of homogenous pores. Among the tested polymers, polystyrene at 10 wt% concentration demonstrated good particle morphology determined to around 1.94–3.45 µm. The addition of surfactant at a concentration of 7–10 wt% during microsphere synthesis resulted in the formation of well-shaped and non-aggregating microsphere particles. In addition, the template has contributed to the production of porous monoliths with enhanced thermal stability. The thermogravimetric analysis (TGA) indicated monolith degradation between 230 °C and 450 °C, implying the material excellent mechanical strength. The findings of the study provide insightful knowledge on the feasibility of polymeric microsphere particles as a pore-directing template to fabricate monoliths with desired pore structures.

Significance Retrotransposons are noninfectious, mobile genetic elements that proliferate in host genomes via an RNA intermediate that is copied into DNA by a reverse transcriptase (RT) enzyme. RTs are important for biotechnological applications involving information capture from RNA since RNA is first converted into complementary DNA for detection or sequencing. Here, we biochemically characterized RTs from two retroelements and uncovered several activities that allowed us to design a streamlined, efficient workflow for determining the inventory of RNA sequences in processed RNA pools. The unique properties of nonretroviral RT activities obviate many technical issues associated with current methods of RNA sequence analysis, with wide applications in research, biotechnology, and diagnostics., Selfish, non-long terminal repeat (non-LTR) retroelements and mobile group II introns encode reverse transcriptases (RTs) that can initiate DNA synthesis without substantial base pairing of primer and template. Biochemical characterization of these enzymes has been limited by recombinant expression challenges, hampering understanding of their properties and the possible exploitation of their properties for research and biotechnology. We investigated the activities of representative RTs using a modified non-LTR RT from Bombyx mori and a group II intron RT from Eubacterium rectale. Only the non-LTR RT supported robust and serial template jumping, producing one complementary DNA (cDNA) from several templates each copied end to end. We also discovered an unexpected terminal deoxynucleotidyl transferase activity of the RTs that adds nucleotide(s) of choice to 3′ ends of single- and/or double-stranded RNA or DNA. Combining these two types of activity with additional insights about nontemplated nucleotide additions to duplexed cDNA product, we developed a streamlined protocol for fusion of next-generation sequencing adaptors to both cDNA ends in a single RT reaction. When benchmarked using a reference pool of microRNAs (miRNAs), library production by Ordered Two-Template Relay (OTTR) using recombinant non-LTR retroelement RT outperformed all commercially available kits and rivaled the low bias of technically demanding home-brew protocols. We applied OTTR to inventory RNAs purified from extracellular vesicles, identifying miRNAs as well as myriad other noncoding RNAs (ncRNAs) and ncRNA fragments. Our results establish the utility of OTTR for automation-friendly, low-bias, end-to-end RNA sequence inventories of complex ncRNA samples.

The scope of the presented research orientates itself towards the development of a Molecularly Imprinted Polymer (MIP)-based dye displacement assay for the colorimetric detection of the antibiotic amoxicillin in aqueous medium. With this in mind, the initial development of an MIP capable of such a task sets focus on monolithic bulk polymerization to assess monomer/crosslinker combinations that have potential towards the binding of amoxicillin. The best performing composition (based on specificity and binding capacity) is utilized in the synthesis of MIP particles by emulsion polymerization, yielding particles that prove to be more homogenous in size and morphology compared to that of the crushed monolithic MIP, which is an essential trait when it comes to the accuracy of the resulting assay. The specificity and selectivity of the emulsion MIP proceeds to be highlighted, demonstrating a higher affinity towards amoxicillin compared to other compounds of the aminopenicillin class (ampicillin and cloxacillin). Conversion of the polymeric receptor is then undertaken, identifying a suitable dye for the displacement assay by means of binding experiments with malachite green, crystal violet, and mordant orange. Once identified, the optimal dye is then loaded onto the synthetic receptor, and the displaceability of the dye deduced by means of a dose response experiment. Alongside the sensitivity, the selectivity of the assay is scrutinized against cloxacillin and ampicillin. Yielding a dye displacement assay that can be used (semi-)quantitatively in a rapid manner.

The biomimetic synthesis of carbonated apatites by biomolecule-based templates is a promising way for broadening apatite applications in bone tissue regeneration. In this work, heparin was used as an organic template to prepare uniform carbonate-based apatite nanorods (CHA) and graft ferulic acid (F-CHA) for enhanced bone mineralization. Next, by combining calcium phosphate cement (CPC) with different F-CHA/CPC ratios, a new type of injectable bone cement combined with F-CHA bioactive apatite was developed (CPC + F-CHA). The physicochemical properties, biocompatibility, and mineralization potential of the CPC + F-CHA composites were determined in vitro. The experimental results confirmed the preparation of highly biocompatible CHA and the compatibility of F-CHA with CPC. Although CPC + F-CHA composites with F-CHA (2.5 wt%, 5 wt%, and 10 wt%) showed a significant reduction in compressive strength (CS), compositing CPC with 10 wt% F-CHA yielded a CS suitable for orthopedic repair (CS still larger than 30 MPa). Spectroscopic and phase analyses revealed that the phase of the hydrothermally synthesized CHA product was not modified by the heparin template. Injection and disintegration tests indicated that the CPC + F-CHA composites have good biocompatibility even at 10 wt% F-CHA. D1 osteoprogenitor cells were cultured with the composites for 7 days in vitro, and the CPC + 10%F-CHA group demonstrated significantly promoted cell mineralization compared with other groups. Given these results, the use of over 10% F-CHA in CPC composites should be avoided if the latter is to be applied to load-bearing areas. A stress-shielding device may also be recommended to stabilize these areas. These newly developed biocompatible CPC + F-CHA have great potential as osteoconductive bone fillers for bone tissue engineering.

International audience; Zeolites are essential materials to industry due to their adsorption and catalytic properties. The best current approach to prepare a targeted zeolite still relies on trial and error's synthetic procedures since a rational understanding of the impact of synthesis variables on the final structures is still missing. To discern the role of a variety of organic templates, we perform simulations of the early stages of condensation of silica oligomers by combining DFT, Brønsted-Evans-Polanyi relationships and kinetic Monte Carlo simulations. We investigate an extended reaction path mechanism including 258 equilibrium reactions and 242 chemical species up to silica octamers, comparing the computed concentrations of Si oligomers with 29SI NMR experimental data. The effect of the templating agent is linked to the modification of the intramolecular H-bond network in the growing oligomer, which produces higher concentration of 4-membered ring intermediates, precursors of the key double-four ring building blocks present on more than 39 known zeolite topologies.

Telomerase is unique among the reverse transcriptases in containing a noncoding RNA (known as telomerase RNA (TER)) that includes a short template that is used for the processive synthesis of G-rich telomeric DNA repeats at the 3′ ends of most eukaryotic chromosomes1. Telomerase maintains genomic integrity, and its activity or dysregulation are critical determinants of human longevity, stem cell renewal and cancer progression2,3. Previous cryo-electron microscopy structures have established the general architecture, protein components and stoichiometries of Tetrahymena and human telomerase, but our understandings of the details of DNA–protein and RNA–protein interactions and of the mechanisms and recruitment involved remain limited4–6. Here we report cryo-electron microscopy structures of active Tetrahymena telomerase with telomeric DNA at different steps of nucleotide addition. Interactions between telomerase reverse transcriptase (TERT), TER and DNA reveal the structural basis of the determination of the 5′ and 3′ template boundaries, handling of the template–DNA duplex and separation of the product strand during nucleotide addition. The structure and binding interface between TERT and telomerase protein p50 (a homologue of human TPP17,8) define conserved interactions that are required for telomerase activation and recruitment to telomeres. Telomerase La-related protein p65 remodels several regions of TER, bridging the 5′ and 3′ ends and the conserved pseudoknot to facilitate assembly of the TERT–TER catalytic core. Cryo-electron microscopy structures of Tetrahymena telomerase with telomeric DNA at several steps of nucleotide addition provide insights into the structural basis of telomere repeat synthesis.

Aquatic birds represent a vast reservoir from which new pandemic influenza A viruses can emerge1. Influenza viruses contain a negative-sense segmented RNA genome that is transcribed and replicated by the viral heterotrimeric RNA polymerase (FluPol) in the context of viral ribonucleoprotein complexes2,3. RNA polymerases of avian influenza A viruses (FluPolA) replicate viral RNA inefficiently in human cells because of species-specific differences in acidic nuclear phosphoprotein 32 (ANP32), a family of essential host proteins for FluPol activity4. Host-adaptive mutations, particularly a glutamic-acid-to-lysine mutation at amino acid residue 627 (E627K) in the 627 domain of the PB2 subunit, enable avian FluPolA to overcome this restriction and efficiently replicate viral RNA in the presence of human ANP32 proteins. However, the molecular mechanisms of genome replication and the interplay with ANP32 proteins remain largely unknown. Here we report cryo-electron microscopy structures of influenza C virus polymerase (FluPolC) in complex with human and chicken ANP32A. In both structures, two FluPolC molecules form an asymmetric dimer bridged by the N-terminal leucine-rich repeat domain of ANP32A. The C-terminal low-complexity acidic region of ANP32A inserts between the two juxtaposed PB2 627 domains of the asymmetric FluPolA dimer, suggesting a mechanism for how the adaptive PB2(E627K) mutation enables the replication of viral RNA in mammalian hosts. We propose that this complex represents a replication platform for the viral RNA genome, in which one of the FluPol molecules acts as a replicase while the other initiates the assembly of the nascent replication product into a viral ribonucleoprotein complex. Structural and biochemical studies of influenza virus RNA polymerase in complex with host acidic nuclear phosphoprotein 32 (ANP32) show how ANP32-mediated polymerase dimerization enables the replication of influenza viral RNA in a host-dependent manner.

DNA-templated synthesis takes advantage of the programmability of DNA-DNA interactions to accelerate chemical reactions under diluted conditions upon sequence-specific hybridization. While this strategy has proven advantageous for a variety of applications, including sensing and drug discovery, it has been so far limited to the use of nucleic acids as templating elements. Here, we report the rational design of DNA templated synthesis controlled by specific IgG antibodies. Our approach is based on the co-localization of reactants induced by the bivalent binding of a specific IgG antibody to two antigen-conjugated DNA templating strands that triggers a chemical reaction that would be otherwise too slow under diluted conditions. This strategy is versatile, orthogonal and adaptable to different IgG antibodies and can be employed to achieve the targeted synthesis of clinically-relevant molecules in the presence of specific IgG biomarker antibodies., DNA-templated synthesis takes advantage of sequence-specific hybridization to accelerate chemical reactions. Here, the authors present templated synthesis controlled through antibody-antigen interactions.

Disulfide-rich macrocyclic peptides-cyclotides, for example-represent a promising class of molecules with potential therapeutic use. Despite their potential their efficient synthesis at large scale still represents a major challenge. Here we report new chemoenzymatic strategies using peptide ligase variants-inter alia, omniligase-1-for the efficient and scalable one-pot cyclization and folding of the native cyclotides MCoTI-II, kalata B1 and variants thereof, as well as of the theta-defensin RTD-1. The synthesis of the kB1 variant T20K was successfully demonstrated at multi-gram scale. The existence of several ligation sites for each macrocycle makes this approach highly flexible and facilitates both the larger-scale manufacture and the engineering of bioactive, grafted cyclotide variants, therefore clearly offering a valuable and powerful extension of the existing toolbox of enzymes for peptide head-to-tail cyclization.

Transcriptional pausing underlies regulation of cellular RNA biogenesis. A consensus pause sequence that acts on RNA polymerases (RNAPs) from bacteria to mammals halts RNAP in an elemental paused state from which longer-lived pauses can arise. Although the structural foundations of pauses prolonged by backtracking or nascent RNA hairpins are recognized, the fundamental mechanism of the elemental pause is less well-defined. Here we report a mechanistic dissection that establishes the elemental pause signal (i) is multipartite; (ii) causes a modest conformational shift that puts γ-proteobacterial RNAP in an off-pathway state in which template base loading but not RNA translocation is inhibited; and (iii) allows RNAP to enter pretranslocated and one-base-pair backtracked states easily even though the half-translocated state observed in paused cryo-EM structures rate-limits pause escape. Our findings provide a mechanistic basis for the elemental pause and a framework to understand how pausing is modulated by sequence, cellular conditions, and regulators., eLife digest The information a cell needs to create a specific protein is encoded in a sequence of precisely organized DNA ‘letters’. Unlocking these instructions requires an enzyme known as RNA polymerase (RNAP for short), which reads the DNA segment and faithfully copies the information to form a strand of RNA. This molecule then relays the genetic message to the machinery that pieces together a protein. An RNAP works by reading a DNA segment and building a matching RNA strand at the same time. The enzyme clamps onto DNA, and threads it letter-by-letter through its reading and building site. For each DNA letter that RNAP reads, the enzyme adds a matching RNA building block onto the budding RNA strand, with DNA and RNA segments then being moved away from the active site. However, RNAP does not usually read a whole gene in one go: there are several ‘pause sites’ in the sequence where it stops and waits for instruction. If the cell needs this protein immediately, it sends signals that encourage RNAP to carry on and even ignore further pause sites; if the protein is not needed at the time, the enzyme is instructed to terminate the RNA-making process. This mechanism is present in species across the tree of life, and is key so that a cell fine-tunes its protein production. Once RNAP has stopped, several well-studied mechanisms kick in to stabilize the enzyme in its waiting position. Yet, it is still unclear how the enzyme, which normally reads 50 to 100 DNA letters per second, is able to come to a halt in the first place. To dissect this mechanism, Saba et al. made targeted changes to RNAP or to the DNA segment it was reading, and then closely monitored the movement of the protein under these conditions. The experiments revealed that when RNAP interacts with multiple signals in the DNA, such as particular sequences just before or inside the segment being read, the enzyme changes its structure slightly, and loosens its grip on DNA and RNA. With the enzyme’s new shape, the RNA strand is ready to be extended, but the DNA segment is trapped and cannot move into the reading site. This prevents a new RNA letter to be added onto the growing strand, stopping RNAP in its tracks. Knowing how RNAP pauses may help researchers to understand how its activity is regulated, for example by antibiotics. Ultimately, this could allow us to manipulate the activity of the enzyme so that we could control how and when a cell creates specific proteins.

Porous ceramics have been developed from lichen templates infiltrated with illite clay slurry and mineralized at 900 ​°C in air and nitrogen environments. The obtained ceramic samples were thoroughly investigated as well as tested for phenol catalytic decomposition ability. The structures of mineralized samples in air and nitrogen environments differ; samples mineralized in air demonstrate poorly structured platelets of plagioclase and mainly quartz, as well as small amorphous areas. The presence of crystalline particles in sizes from 400 up to 850 ​nm and attributed to carbon or iron is typical for samples mineralized in nitrogen. The effect on phenol catalytic decomposition can be evaluated as 80% effective decomposition after contact of samples with phenol-water solution. One of the main factors for catalytic decomposition of phenol is considered to be the presence of differently located Fe3+,2+ ions in the structure of samples with the decomposition process being akin to Fenton reactions.

Poly(PADPA) synthesized with the enzyme Trametes versicolor laccase (TvL) at pH = 3.5 in aqueous solution from the aniline dimer p -aminodiphenylamine (PADPA) was studied by EPR spectrometry at X-band and W-band frequencies. For the synthesis of poly(PADPA), vesicles formed from AOT (sodium bis-(2-ethylhexyl)sulfosuccinate) were used as structure-directing templates, and TvL/O 2 as catalyst and oxidant. The isolated product is abbreviated as “poly(PADPA)-TvL-AOT” to distinguish it from poly(PADPA) obtained by other means. The EPR spectrum of poly(PADPA)-TvL-AOT recorded at room temperature is complex. It can be decomposed into two separate Dyson–type spectral components. Furthermore, the spectra measured at high frequency exhibit a line broadening behavior in comparison to the spectra recorded at low frequency where there is no line broadening. This behavior was used to estimate the effective inter -chain spin exchange interaction for each monitored spectral component. The obtained effective distances between the polymer (or oligomer) chains in both identified components of poly(PADPA)-TvL-AOT can be explained by considering slightly different interactions between the chains and the AOT molecules present in the sample. Additionally, due to different average g tensor values, g av , of these components, it seems that each spectral component originates from one of two different molecular subunits (or local structural motifs) within the polymer (or oligomer) chains.

Polymers 10(4), 429 (2018). doi:10.18154/RWTH-2018-223567 special issue: "Special Issue "Microgels and Hydrogels at Interfaces" / Guest Editor Dr. Patrick van Rijn, Department of BioMedical Engineering FB-40, University of Groningen/University Medical Center Groningen; Dr. Felix Plamper, Institute of Physical Chemistry, RWTH Aachen University", Published by MDPI, Basel

Viruses in the Reoviridae, like the triple-shelled human rotavirus and the single-shelled insect cytoplasmic polyhedrosis virus (CPV), all package a genome of segmented double-stranded RNAs (dsRNAs) inside the viral capsid and carry out endogenous messenger RNA synthesis through a transcriptional enzyme complex (TEC). By direct electron-counting cryoelectron microscopy and asymmetric reconstruction, we have determined the organization of the dsRNA genome inside quiescent CPV (q-CPV) and the in situ atomic structures of TEC within CPV in both quiescent and transcribing (t-CPV) states. We show that the ten segmented dsRNAs in CPV are organized with ten TECs in a specific, non-symmetric manner, with each dsRNA segment attached directly to a TEC. The TEC consists of two extensively interacting subunits: an RNA-dependent RNA polymerase (RdRP) and an NTPase VP4. We find that the bracelet domain of RdRP undergoes marked conformational change when q-CPV is converted to t-CPV, leading to formation of the RNA template entry channel and access to the polymerase active site. An amino-terminal helix from each of two subunits of the capsid shell protein (CSP) interacts with VP4 and RdRP. These findings establish the link between sensing of environmental cues by the external proteins and activation of endogenous RNA transcription by the TEC inside the virus.

International audience; Highly-ordered arrays with sub-10 nm features are produced with topographical-directed self-assembly of low-molecular-weight poly(1,1-dimethyl silacyclobutane)block-poly(methyl methacrylate). This system turns out to be of high interest for lithographic applications since the domain orientation is solely controlled through the polymer layer thickness, while the promotion of the microphase separation is obtained by a short thermal annealing process under mild conditions.

Nanostructured polymer/silica hybrid materials have gained attention as they combine the advantageous properties of organic and inorganic materials in one entity. Herein, we report incorporation of chloromethyl moieties into a living diatom to prepare an alkyl-halide activated siliceous biotemplate. Subsequent, in situ polymerization via surface initiated atom transfer radical polymerization generated a polymer/silica microparticle with defined geometry., This material is based upon works supported by the Science Foundation Ireland under Grant no. [07/SRC/B1163]. The authors acknowledge the facilities and scientific and technical assistance of the Centre for Microscopy and Imaging at the National University of Ireland Galway funded by NUIG and the Irish Government's Programme for Research in Third Level Institutions, Cycles 4 and 5, National Development Plan 2007–2013.

Basic adsorption of hydrophobic polymers from aprotic solvents was introduced as a platform technology to modify exclusively the surfaces of cellulose nanopapers. Dynamic vapor sorption demonstrated that the water vapor uptake ability of the nanopapers remained unperturbed, despite strong repellency to liquid water caused by the adsorbed hydrophobic polymer on the surface. This was enabled by the fact that the aprotic solvents used for adsorption did not swell the nanopaper unlike water that is generally applied as the adsorption medium in such systems. As case examples, the adsorptions of polystyrene (PS) and poly(trifluoroethylene) (PF3E) were followed by X-ray photoelectron spectroscopy and water contact angle measurements, backed up with morphological analysis by atomic force microscopy. The resulting nanopapers are useful in applications like moisture buffers where repellence to liquid water and ability for moisture sorption are desired qualities.

The recent outbreak of Zika virus (ZIKV) has imposed a serious threat to public health. Here we report the crystal structure of the ZIKV NS5 protein in complex with S-adenosyl-L-homocysteine, in which the tandem methyltransferase (MTase) and RNA-dependent RNA polymerase (RdRp) domains stack into one of the two alternative conformations of flavivirus NS5 proteins. The activity of this NS5 protein is verified through a de novo RdRp assay on a subgenomic ZIKV RNA template. Importantly, our structural analysis leads to the identification of a potential drug-binding site of ZIKV NS5, which might facilitate the development of novel antivirals for ZIKV., The recent outbreak of Zika virus is a major worldwide health concern and effective drugs are currently not available. Here the authors present the structure of Zika non-structural protein 5 and identify a potential drug-binding site, which might facilitate the development of novel antivirals.

Anisotropic nanostructtires, such as nanotubes, incorporating bioactive molecules present interesting features for application as drug delivery carriers. Here, we present the synthesis of layer-by-layer (LbL) nanotubes including protein (ovalbumin) layers and go from simple to more complex synergetic combinations of synthetic and natural polyelectrolytes, leading to structures with tunable properties. The rigidity in organic and aqueous media, the stability in buffer solution and the uptake of different LbL tubes by dendritic cells (DCs) are analyzed to contrast size and chemistry. The most rigid studied systems appear as the best candidates to be internalized by cells, regardless of the chemistry of their outermost layers. The successful transport of long protein-loaded robust rigid nanotubes to the cytoplasm of DCs paves the way for their use as new cargo for the delivery of large amounts of antigen to such cells.

Several CeO2 and CuO-CeO2 catalysts were prepared using different methods, i.e., a homogeneous precipitation with urea, a nanocasting route using CMK-3 carbon as a hard template and a sol–gel process using Poly(methyl methacrylate) (PMMA) polymer as a soft template, and tested in the total oxidation of propane. The catalysts were characterized by a number of physicochemical techniques (XRD, N2 adsorption, TPR, XPS, Raman spectroscopy) showing distinct characteristics. For each series, Cu-Ce-O catalysts with low Cu-loadings (5 wt % CuO) showed the highest activity, higher than those samples either without copper or with high Cu-loading (13 wt % CuO). The incorporation of copper leads to an increase of the concentration of bulk defects but if the Cu-loading is too high the surface area drastically falls. The highest activity in the total oxidation of propane was achieved by Cu-containing ceria catalysts synthesized using a polymer as a template, as this method yields high surface area materials. The surface area and the number of bulk/sub-surface defects of the ceria seem to be the main properties determining the catalytic activity., The authors would like to acknowledge the DGICYT in Spain CTQ2012-37925-C03-2, CTQ2015-68951-C3-1-R, CTQ2015-68951-C3-3-R. Authors from ITQ also thank Project SEV-2012-0267 for financial support. B.S, R.S and A.M.D also thank UV-INV-AE16-484416.

A series of shape-persistent phenylene–ethynylene–naphthylene–butadiynylene macrocycles with different extraannular alkyl groups and intraannular bridges is synthesized by oxidative Glaser-coupling of the appropriate precursors. The intraannular bridges serve in this case as templates that reduce the oligomerization even when the reaction is not performed under pseudo high-dilution conditions. The extraannular as well as the intraannular substituents have a strong influence on the thermal behavior of the compounds. With branched alkyl chains at the periphery, the macrocycles exhibit liquid crystalline (lc) phases when the interior is empty or when the length of the alkyl bridge is just right to cross the ring. With a longer alkyl or an oligoethylene oxide bridge no lc phase is observed, most probably because the mesogene is no longer planar.

ZnO-SnO2 hollow spheres were successfully synthesized through a hydrothermal method-combined carbon sphere template. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR). The average diameter of hollow spheres is about 150 nm. The photocatalytic activity of the as-prepared samples was investigated by photodegrading Rhodamine B. The results indicated that the photocatalytic activities of ZnO-SnO2 hollow spheres are higher than ZnO hollow spheres. The degradation efficiency of the hollow spheres could reach 99.85% within 40 min, while the ZnO hollow spheres need 50 min.

WOS: 000324103300007, The influence of poly(ethylene glycol) (PEG) and synthesis temperature in the synthesis of SBA-15-SO3H was investigated to evaluate the catalytic activity in the esterification of propionic acid with methanol. The catalysts were characterized by means of surface and structure analyses; X-ray diffraction, FT-IR, scanning electron microscopy, Thermo-gravimetric and N-2 adsorption/desorption techniques. It was found that, by the addition of PEG, the surface area and porosity of SBA-15-SO3H increased, while the structure and size of mesopores remained unchanged. Nitrogen sorption measurements indicate that PEG introduces additional pores into the pore walls of SBA-15-SO3H. Thus, a simple way of improving the porosity of mesoporous SBA-15-SO3H was presented that could enhance transport of substrates through the porous system and allow the generation of stable mesoporous replicas, important for catalytic applications and also beneficial for replication and nanocasting purposes., Commission of Scientific Research Projects of Uludag University [UAP(F)-2011/69], This work was supported by The Commission of Scientific Research Projects of Uludag University, Project number: UAP(F)-2011/69.

Nanoporous silicon oxide templates formed by swift heavy ion tracks technology have been investigated. The influence of the heavy ion characteristics, such as type of ion, energy, stopping power and irradiation fluence on the pore properties of the silicon oxide templates, has been studied. Furthermore, the process of pore formation by chemical etching with hydrofluoric acid has been thoroughly investigated by assessing the effect of etchant concentration and etching time. The outcome of this investigation enables us to have precise control over the resulting geometry of nanopores arrays. As a result, guidelines for the creation of a-SiO2/Si templates with tunable parameters and general recommendations for their further application are presented.

Current genome-editing technologies introduce double-stranded (ds) DNA breaks at a target locus as the first step to gene correction.1,2 Although most genetic diseases arise from point mutations, current approaches to point mutation correction are inefficient and typically induce an abundance of random insertions and deletions (indels) at the target locus from the cellular response to dsDNA breaks.1,2 Here we report the development of base editing, a new approach to genome editing that enables the direct, irreversible conversion of one target DNA base into another in a programmable manner, without requiring dsDNA backbone cleavage or a donor template. We engineered fusions of CRISPR/Cas9 and a cytidine deaminase enzyme that retain the ability to be programmed with a guide RNA, do not induce dsDNA breaks, and mediate the direct conversion of cytidine to uridine, thereby effecting a C→T (or G→A) substitution. The resulting “base editors” convert cytidines within a window of approximately five nucleotides (nt), and can efficiently correct a variety of point mutations relevant to human disease. In four transformed human and murine cell lines, second- and third-generation base editors that fuse uracil glycosylase inhibitor (UGI), and that use a Cas9 nickase targeting the non-edited strand, manipulate the cellular DNA repair response to favor desired base-editing outcomes, resulting in permanent correction of ∼15-75% of total cellular DNA with minimal (typically ≤ 1%) indel formation. Base editing expands the scope and efficiency of genome editing of point mutations.

Carbon foams were produced from a macroporous poly(divinylbenzene) (poly(DVB) precursor, synthesized by polymerizing the continuous but minority phase of water-in-oil high internal phase emulsions (HIPEs) stabilized by molecular and/or particulate emulsifiers. Both permeable and non-permeable hierarchically porous carbon foams, or ‘carboHIPEs’, were prepared by carbonization of the resulting macroporous polymers at 800 °C. The carbon yields were as high as 26 wt.% of the original polymer. CarboHIPEs retain the pore structure of the macroporous polymer precursor, but with surface areas of up to 505 m2/g and excellent electrical conductivities of 81 S/m. Contrary to some previous reports, the method does not require further modification, such as sulfonation or additional crosslinking of the polyHIPE prior to carbonization, due to the inherently crosslinked structure of poly(DVB). The use of a pourable, aqueous emulsion-template enables simple moulding, minimises waste and avoids the strong acid treatments used to remove many conventional solid-templates. The retention of the macroporous structure is coupled with the introduction of micropores during carbonization, producing hierarchically porous carboHIPEs, suitable for a wide range of applications as sorbents and electrodes.

One central problem for the function and manufacture of materials where performance relies on nanoscale structure is to control the compatibility and interactions of the building blocks. In natural materials, such as nacre, there are examples of multifunctional macromolecules that have combined binding affinities for different materials within the same molecule, thereby bridging these materials and acting as a molecular glue. Here, we describe the use of a designed multifunctional protein that is used for self-assembly of nanofibrillar cellulose. Recent advances in the production of cellulose nanofibrils have given inspiration for new uses of cellulosic materials. Cellulose nanofibrils have mechanical and structural features that open new possibilities for performance in composites and other nanoscale materials. Functionalisation was realised through a bi-functional fusion protein having both an ability to bind to cellulose and a second functionality of surface activity. The cellulose-binding function was obtained using cellulose-binding domains from cellulolytic enzymes and the surface activity through the use of a surface active protein called hydrophobin. Using the bi-functional protein, cellulose nanofibrils could be assembled into tightly packed thin films at the air/water interface and at the oil/water interface. It was shown that the combination of protein and cellulose nanofibrils resulted in a synergistic improvement in the formation and stability of oil-in-water emulsions resulting in emulsions that were stable for several months. The bi-functionality of the protein also allowed the binding of hydrophobic solid drug nanoparticles to cellulose nanofibrils and thereby improving their long-term stability under physiological conditions.

A new type of biomimetic templated copolymer has been prepared by reverse addition fragmentation chain transfer polymerization (RAFT) in dioxane. The initial formulation includes the template fluorescein, N-isopropylacrylamide (NIPAM, 84 mol %), methacrylic acid (MAA, 5-mol %), 4-vinylpyridine (4-VP, 9 mmol %), and N,N′-methylenebis(acrylamide) (MBA, 2 mol %). PolyNIPAM is a thermosensitive polymer that comes out of aqueous solution above its lower critical solution temperature forming hydrophobic ‘crosslinks’. MAA and 4-VP interact in dioxane forming acid–base crosslinks. The excess 4-VP serves as a recognition monomer organizing around the template fluorescein to form a binding site that is held in place by the noncovalent and covalent crosslinks. The MBA is a covalent crosslinker. The RAFT agent in the resulting copolylmer was reduced to a thiol and attached to gold nanoparticles. The gold nanoparticle bound copolymer binds fluorescein completely in less than two seconds with an affinity constant greater than 108 M−1. A reference copolymer prepared with the same monomers by the same procedure binds fluorescein much more weakly.

Anodised aluminium oxide (AAO) templates have been utilised to investigate Cu deposition from a typical sulphate plating bath. The influence of the common additives poly ethylene glycol (PEG), chloride ion (Cl−) and Bis-(sodium sulphopropyl)-disulphide (SPS) on the deposition process has been analysed. The growth of Cu wires or nanotubes (with tube walls of 40–70 nm) is significantly influenced by the action of the additives. In the presence of either Cl− or SPS solid wire growth is observed, however, when PEG is added with Cl− the growth of ordered Cu nanotubes is observed. SPS added to a bath containing Cl− and PEG restores the growth of wires. Keywords: Templates, AAO, Copper, Electrodeposition, Nanotubes, Additives

Using diethyl ether as a co-solvent, a non-stable interface of biphasic oil-water system (the so-called oil-water two-phase (OWTP) system) was employed in the preparation of mesostructured silicas with diversified particle morphologies. By adjusting the molar ratios of H2O:C2H5OC2H5:NH3 center dot H2O and the alkalinity of the OWTP system, several product morphologies could be obtained under different reaction conditions. On the other hand, different product morphologies with distinct structural properties could be obtained at a specific reaction condition, indicating that product morphology varied upon intrinsic characteristics of non-equilibrium processes in the system as well. There are six kinds of product morphologies in our results. In the biphasic region the morphotypes such as vesicles, slices, and spheres were widely distributed. Multi-lamellar fragments were formed under relatively strong alkaline conditions and at a high proportion of diethyl ether (>41%). bi-continuously phased fragments were observed in the weak alkaline conditions and medium proportion between diethyl ether and water. In the single-phase region, hexagonally ordered MCM-41, plain sheets of MCM-48, as well as smooth and plain slices with worm-like pore structures were formed with bi-modal pore-size distribution structure. Based on HRTEM analysis, these structural features were rationalized being derived from fragments that originated from the oil/water interface. Apparently, the product morphosynthesis resulted from a combination of fluid theological distortions and reconstructive reaction fields. With a systematic approach we have established the reaction phase diagram of the system, which enabled us to define the structural properties and to classify the morphology of the products for nomenclatural purposes in studying OWTP systems. (c) 2007 Elsevier Inc. All rights reserved.

Extremely dilute systems arise in homeopathy, which uses dilution factors 10(60), 10(400) and also higher. These amounts to potencies of 30c, 200c or more, those are far beyond Avogadro's number. There is extreme skepticism among scientists about the possibility of presence of starting materials due to these high dilutions. This has led modern scientists to believe homeopathy may be at its best a placebo effect. However, our recent studies on 30c and 200c metal based homeopathic medicines clearly revealed the presence of nanoparticles of starting metals, which were found to be retained due to the manufacturing processes involved, as published earlier.(9,10) Here, we use HR-TEM and STEM techniques to study medicines arising from inorganic salts as starting materials. We show that the inorganic starting materials are present as nano-scale particles in the medicines even at 1 M potency (having a large dilution factor of 10(2000)). Thus this study has extended our physicochemical studies of metal based medicines to inorganic based medicines, and also to higher dilution. Further, we show that the particles develop a coat of silica: these particles were seen embedded in a meso-microporous silicate layer through interfacial encapsulation. Similar silicate coatings were also seen in metal based medicines. Thus, metal and inorganic salt based homeopathic medicines retain the starting material as nanoparticles encapsulated within a silicate coating. On the basis of these studies, we propose a universal microstructural hypothesis that all types of homeopathic medicines consist of silicate coated nano-structures dispersed in the solvent.

DNA methylation at selective cytosine residues (5-methylcytosine (5mC)) and their removal by TET-mediated DNA demethylation are critical for setting up pluripotent states in early embryonic development. TET enzymes successively convert 5mC to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC), with 5fC and 5caC subject to removal by thymine DNA glycosylase (TDG) in conjunction with base excision repair. Early reports indicate that 5fC and 5caC could be stably detected on enhancers, promoters and gene bodies, with distinct effects on gene expression, but the mechanisms have remained elusive. Here we determined the X-ray crystal structure of yeast elongating RNA polymerase II (Pol II) in complex with a DNA template containing oxidized 5mCs, revealing specific hydrogen bonds between the 5-carboxyl group of 5caC and the conserved epi-DNA recognition loop in the polymerase. This causes a positional shift for incoming nucleoside 5'-triphosphate (NTP), thus compromising nucleotide addition. To test the implication of this structural insight in vivo, we determined the global effect of increased 5fC/5caC levels on transcription, finding that such DNA modifications indeed retarded Pol II elongation on gene bodies. These results demonstrate the functional impact of oxidized 5mCs on gene expression and suggest a novel role for Pol II as a specific and direct epigenetic sensor during transcription elongation.

Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, have high porosity, high surface-to-volume and strength-to-weight ratio. Unfortunately, common approaches for preparation of metallic nanostructures render materials with highly disordered architecture, which might have an adverse effect on their mechanical properties. Block copolymers have the ability to self-assemble into ordered nanostructures and can be applied as templates for the preparation of well-ordered metal nanofoams. Here we describe the application of a block copolymer-based supramolecular complex -polystyrene-block-poly(4-vinylpyridine)(pentadecylphenol) PS-b-P4VP(PDP) - as a precursor for well-ordered nickel nanofoam. The supramolecular complexes exhibit a phase behavior similar to conventional block copolymers and can self-assemble into the bicontinuous gyroid morphology with two PS networks placed in a P4VP(PDP) matrix. PDP can be dissolved in ethanol leading to the formation of a porous structure that can be backfilled with metal. Using electroless plating technique, nickel can be inserted into the template's channels. Finally, the remaining polymer can be removed via pyrolysis from the polymer/inorganic nanohybrid resulting in nanoporous nickel foam with inverse gyroid morphology.

We present a detailed experimental and theoretical investigation of the ultrathin titania z'-TiOx/Pt(111) phase and Au nanoparticles assembled on it. Scanning tunneling spectroscopy (STS) at two different tip stabilization biases (TSB) is measured at three different locations on the bare titania phase and on top of the Au nanoparticles (NPs). STS data are compared with the results of first-principles calculations based on a Tersoff-Hamann approach for simulating tunneling currents. We obtain a coherent framework in which STS features can be used as fingerprints with atomistic resolution of the local density of states. On the bare titania, Shockley states coming from the 0 atoms dominate the occupied DOS, while resonant states coming from the Ti atoms dominate the DOS above the Fermi level. The ultrathin film is partially metallized, with DOS empty channels at the hole sites, hence lying in an intermediate state between a semiconducting oxide and a conductor. Finally, STS data on top of Au nanoparticles provide information on the coordination environment of the Au atom in direct contact with the titania phase, discriminating between the Au metallic or nonmetallic regime.

International audience; Lightweight cellular foams were prepared by freeze-drying oil-in-water emulsions stabilized with cellulose nanocrystals (CNCs). Oil and water were removed while preserving the cellular emulsion template without any shrinkage or deformation both at the internal cell and bulk foam scales. This versatile process proved to be relevant for controlling the pore size of the foam with respect to emulsion droplets. Moreover, the composite foams could easily be obtained as shown here by the addition of polyelectrolytes. Mechanical properties of the foam were investigated and they were found to be reinforced by chitosan addition. Thus, our finding opens new routes to a broad range of cellulose-based porous materials.

The effects of temperature and interfacial elasticity on nanostructured titanium dioxide (TiO2) microemulsions templated materials have been investigated. The aim was to establish a simple and rapid selection of the best experimental conditions for achieving some required material property. TiO2 materials have been prepared through reactive microemulsion precipitation. The effect of microemulsion process parameters (temperature and oil phase density) on the final material characteristics has been investigated. The titania nanopowders were characterized by Xray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and N2 adsorption– desorption isotherms. The results obtained by different process conditions show that the nonpolar phase density and temperature of microemulsions have a great influence on the final characteristics of the obtained material. A reduction of the microemulsion oil density causes a significant decrease in the particle agglomeration and an augment of the material-specific surface area and pore volume. At the same time, rutile is favored over anatase phase. The increase of template microemulsion temperature produces, in some systems, a morphology change from granular to a bicontinuous structure. Fil: Messina, Paula Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Bahía Blanca. Instituto de Química del Sur; Argentina.; Fil: Verdinelli, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Bahía Blanca. Instituto de Química del Sur; Argentina.; Fil: Pieroni, Olga Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Bahía Blanca. Instituto de Química del Sur; Argentina.; Fil: Ruso, Juan Manuel. Universidad de Santiago de Compostela. Facultad de Física. Grupo de Materia Blanda y Biofísica Molecular; España

Low-temperature processing of dye-sensitized solar cells (DSCs) is crucial to enable commercialization with low-cost, plastic substrates. Prior studies have focused on mechanical compression of premade particles on plastic or glass substrates; however, this did not yield sufficient interconnections for good carrier transport. Furthermore, such compression can lead to more heterogeneous porosity. To circumvent these problems, we have developed a low-temperature processing route for photoanodes where crystalline TiO2 is deposited onto well-defined, mesoporous templates. The TiO2 is grown by atomic layer deposition (ALD), and the crystalline films are achieved at a growth temperature of 200 °C. The ALD TiO2 thickness was systematically studied in terms of charge transport and performance to lead to optimized photovoltaic performance. We found that a 15 nm TiO2 overlayer on an 8 μm thick SiO2 film leads to a high power conversion efficiency of 7.1% with the state-of-the-art zinc porphyrin sensitizer and cobalt bipyridine redox mediator.

The possibility of using self-assembled films of block polymers as templates to fabricate nanoscale structures for devices has attracted great attention towards this class of material. Self-assembly of a block copolymer can be directed by using an electric field to orient features (i.e., similar to10-nm-diam cylinders) parallel to the electric field, making the material more attractive as a nanoscale lithography mask. In this letter we describe an approach to influence the electric field orientation phenomena by interfacial effects. As a result, the 15-nm-diam polystyrene cylinders of the polystyrene-polyisoprene-polystyrene triblock copolymer orient perpendicular to the electric field. The described approach along with the previous method can produce a directed self-assembly to fabricate complex nanoscale structures with orthogonally oriented nanoscale width lines. (C) 2003 American Institute of Physics. Carilion Biomedical Institute

International audience; During the origin of life, the biological information of nucleic acid polymers must have increased to encode functional molecules (the RNA world). Ribozymes tend to be compositionally unbiased, as is the vast majority of possible sequence space. However, ribonucleotides vary greatly in synthetic yield, reactivity and degradation rate, and their non-enzymatic polymerization results in compositionally biased sequences. While natural selection could lead to complex sequences, molecules with some activity are required to begin this process. Was the emergence of compositionally diverse sequences a matter of chance, or could prebiotically plausible reactions counter chemical biases to increase the probability of finding a ribozyme? Our in silico simulations using a two-letter alphabet show that template-directed ligation and high concatenation rates counter compositional bias and shift the pool toward longer sequences, permitting greater exploration of sequence space and stable folding. We verified experimentally that unbiased DNA sequences are more efficient templates for ligation, thus increasing the compositional diversity of the pool. Our work suggests that prebiotically plausible chemical mechanisms of nucleic acid polymerization and ligation could predispose toward a diverse pool of longer, potentially structured molecules. Such mechanisms could have set the stage for the appearance of functional activity very early in the emergence of life.

Metal nanofoams with a porosity above 50% v/v have recently attracted great. Interest In materials science due to their interesting properties.. We.. demonstrate a new straightforward route to prepare such nanofoams using diblock copolymer-based PS-block-P4VP-(PDP) supramolecules that self-assemble Into a bicontinuous gyroid morphology, consisting of PS network channels in a P4VP(PDP) matrix. After dissolving the PDP, the P4VP. collapses onto the PS struts and a free-standing bicontinuous. gyroid template of 50-100 mu m thickness and interconnected, uniformly sized pores Is formed. The hydrophilic P4VP corona facilitates the penetration of water-based plating reagents into the porous template and enables a successful metal deposition. After plating, the polymer is simply degraded by heating, resulting In a well-ordered inverse gyroid nickel-foam. Essential to this approach Is the removal of only one part of the matrix (i.e., PDP). Therefore, the template accounts for 50% v/v or more. The porosity characteristics (amount, size of pores) can be tuned by selecting the appropriate copolymer and by adjusting the amount of PDP.

International audience; This paper discusses the self-assembly of rod-coil amylose-b-polystyrene (Mal-b-PS) block copolymer thick and thin films. The nano-organization falls in an interdomain spacing d of about 10 am, much smaller than flexible-flexible petrol block copolymer systems. Additionally, hydrogen-bonding interactions between carbohydrate rods (amylose) and 4',4-bipyridine (bipy) molecules induces phase transitions. Indeed, adding bipy in maltooctadecaose-block-polystyrene (Mal18-b-PS) copolymers results, at room temperature, in the formation of a lamellar phase having Mal18 bipy-rich nanodomains instead of hexagonal close-packed (HCP) of cylinders made of Mal18, whereas a coexistence of Mal7bipy-rich cylindrical and spherical nanodomains are formed from maltoheptaose-b-polystyrene (Mal7-b-PS) copolymers instead of a poorly organized array of Mal7-based cylinders. On heating, the Mal7bipy-b-PS system shows more rich phase behavior as compared to the Mal7-b-PS one due to weakening of hydrogen bonding with temperature. Such a system is of great interest in developing active layers in light-emitting diodes (LEDs) or in photovoltaic cells to realize devices with an optimal structure, that is, having large interface area and domain size with similar exciton diffusion length (10 nm).

The well-defined structure and high stability of peptides make them attractive biotemplates for low-temperature synthesis of semiconductor nanocrystals. Adsorbed peptide monolayers could also potentially passivate semiconductors by preventing regrowth of the oxide layer. In this work, the adsorption and passivation capabilities of different collagen-binding peptides on In As surfaces were analyzed by X-ray photoelectron spectroscopy (XPS). Before peptide functionalization, Br(2)- and HCl-based etches were used to remove the native oxide layer on the In As surfaces. The presence of the N is peak for peptide-functionalized samples confirms the adsorption of peptides onto the etched In As surfaces. Calculated coverages were similar for all peptide sequences and ranged from similar to 20 to 40% of a monolayer using the deconvoluted C Is spectra and from similar to 2 to 5% for the N Is spectra. The passivation ability of the peptides was analyzed by comparing the ratios of the oxide components to the nonoxide components in the XPS spectra. The thickness of the oxide layer was also approximated by accounting for the attenuation of the substrate photoelectrons through the oxide layer. We find that the oxide layer regrowth still occurs after peptide functionalization. However, the oxide layer thicknesses for peptide-functionalized samples do not reach as received levels, indicating that the peptides do have some passivation ability on InAs.

Cataloged from PDF version of article. The zinc nitrate salt acts as a solvent in the ZnX-C(12)EO(10) (ZnX is [Zn(H(2)O)(6)](NO(3))(2) and C(12)EO(10) is C(12)H(25)(OCH(2)CH(2))(10)OH) lyotropic liquid crystalline (LLC) mesophase with a drastic dropping on the melting point of ZnX. The salt surfactant LLC mesophase is stable down to -52 degrees C and undergoes a phase change into a solid mesostructured salt upon cooling below -52 degrees C; no phase separation is observed down to -190 degrees C. The ZnX-C(12)EO(10) mesophase displays a usual phase behavior with an increasing concentration of the solvent (ZnX) in the media with an order of bicontinuous cubic(V(1))-2D hexagonal(H(1)) - a mixture of 2D hexagonal and micelle cubic(H(1) + I)-micelle cubic(I)-micelle(L(1)) phases. The phase behaviors, specifically at low temperatures, and the first phase diagram of the ZnX-C(12)EO(10) system was investigated using polarized optical microscopy (POM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), and Raman techniques and conductivity measurements.

A new, fast, one-pot synthesis of SnO2 and Pt-doped SnO2 inverted opal thin films, to be used as materials for gas sensing, was carried out. Films were built from crystalline cassiterite nanoparticles, uniform in size (∼5 nm), resulting in a well-organized hierarchical structure of macro- and mesopores. The noble metal was homogeneously dispersed into the sensing layer of the oxide and the doping centers were present as Pt(IV) and Pt(II) species, partially reduced to Pt(0) after the interaction with the reducing gas (CO). The values of the electrical sensitivity under CO/Air atmosphere demonstrated that the response of Pt-doped films is higher than that of bare SnO2 films, and that the response of inverted opal films is higher compared to that of the sol-gel films. The regular array of cassiterite nanoparticles, strongly interconnected and ordered as close-packed hollow spheres, promotes the effective gas diffusion through the oxide layer and, along with the electron acceptor ability of Pt(IV) doping centers, significantly contributes to enhancing the electrical sensitivity. The conductance regime of the Pt-doped SnO2 inverted opal film is indicative of a regular microstructure of SnO2 nanoparticles

The interest in the template-based synthesis of nanomaterials and nanostructures is continuously increasing due to the advantageous features offered by the templates and the ease of processing a large number of nanostructures in parallel. In recent years, nanoporous anodic aluminum oxide (AAO) has been intensively studied and used for that purpose. [1] At present, it is considered one of the most promising templates [2] mainly because of its unique features, which include easily tunable geometrical parameters, mild preparation conditions, and resistance to high temperatures. AAO, whichisatypicalself-orderednanopore-arraymaterialformed by the electrochemical oxidation of Al in acidic solutions, is an excellent starting host material for the fabrication of various nanomaterials and nanostructures. It possesses a hexagonally packed arrangement of nanoscale-sized straight blind holes aligned perpendicular to the surface. The voids of the nanoscale-channeled structure are typically filled with various materials and heterostructures using electrochemical or chemical vapor deposition methods after the elimination of the oxide barrier layer that closes the bottom ends of the holes. While this barrier layer is typically considered undesirable and eliminated, herein we emphasize that the surface of this layer possesses an ordered array of hemispheres that can also be used as a very interesting template. We describe the advantages of the ordered bumpy surface for creating artificial superconducting pinning centers in Nb films deposited on it.

Functionalization of colloidal particles based on the use of polyelectrolytes and heterocoagulation was combined with electrophoretic deposition (EPD), with the aim of depositing titania-polystyrene (TiO2-PS) composite particles on Ti6A14V substrates. The composite particles were obtained by heterocoagulation of TiO2 nanoparticles on the surface of monosized polystyrene beads of 4.6 mu m in diameter. Two alternative methods were developed for the preparation of the TiO2-PS suspensions in organic fluids for cathodic electrodeposition. The first method was carried out in alkaline aqueous medium with the use of polyelectrolytes and intermediate control measurements of zeta potential, conductivity, and pH; the second one was carried out directly in the organic solvent used for EPD, typically isopropanol. Examples of deposits obtained by EPD in both suspensions and a comparative analysis between the two methods are presented. (c) 2007 Elsevier Inc. All rights reserved.

Sub-micrometer-sized hollow tantalum oxide (Ta2O5) spheres with tunable shell thickness and void size have been fabricated exploiting P-diketone-functionalized polystyrene (PS) beads as sacrificial templates in a sol-gel process. First, a controlled precipitation of Ta2O5 nanoparticles was carried out on the template surface by hydrolyzing tantalum ethoxide (Ta(OEt)(5)) at room temperature, and subsequently, the polymer core was removed either via chemical treatment with toluene or calcination at 650 degrees C. The thickness of the tantala shell precipitated on the PS core during the coating process was tuned between 100 and 142 nm by varying the concentration of tantala precursor in the reaction media. The obtained Ta2O5-coated PS particles and hollow microspheres were characterized by scanning electron microscopy, transmission electron microscopy, infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. Due to the unique optical and dielectric properties, these nanostructured materials are envisaged to be used in applications such as novel building blocks for the fabrication of advancedmaterials, surface coatings, catalysts, and drug delivery systems. Langmuir

Submicron hollow spheres are an interesting class of materials that receive significant attention nowadays. Closed and mechanically robust homogeneous hollow titania microspheres with as much shell thickness as 130 nm were fabricated by coating polystyrene beads with titania nanoparticles using sol-gel chemistry and subsequently removing the core either via heating or a chemical dissolution process. The thickness of the titania shell deposited on polystyrene core was finely tuned between 100 and 130 nm by varying the concentration of titania precursor, i.e., Ti(OEt)(4) salt from 0.5 to 2 mM during the coating process. The obtained hybrid core-shell particles and hollow microspheres were characterized by scanning electron microscopy, transmission electron microscopy, infrared spectroscopy, X-ray diffraction, and thermo-gravimetric analysis. The approach employed is well suited to the preparation of titania-coated polystyrene hybrid particles and hollow titania spheres, which can find their applications as novel building blocks with unique optical properties for fabrication of advanced materials, catalyst, and drug delivery system. Colloid and Polymer Science