Selective photocatalytic reduction of selenate over TiO2 in the presence of nitrate and sulfate in mine-impacted water.

Selenium contamination is a critical global issue across numerous industries. Industrial waters such as mine-impacted water (MIW) can contain toxic levels of selenate, in addition to varying concentrations of many different dissolved species from the underlying strata, such as sulfate, carbonate, nitrate, organic matter, and many dissolved metals. The removal of selenate from MIW is desired, due to selenate's acute and chronic toxicity in aquatic ecosystems at elevated concentrations. However, due to the complexity of the water matrix and the presence of many other dissolved constituents, this is often very challenging. In this study, we present for the first time the reduction of selenate in a real industrial wastewater, namely MIW, and reveal a significant advantage of photocatalytic reduction; the ability to selectively reduce selenate from >500 µg L-1 to <2 µg L-1 in the presence of the more energetically favourable electron acceptor, nitrate (250× molar concentration of selenate) and high concentrations of sulfate (1,940× molar concentration of selenate). The presence and impacts of sulfate, chloride, carbonate, and nitrate on the competitive adsorption and reduction of selenate on TiO2 are thoroughly investigated for the first time, using formic acid as an electron hole scavenger. The electron transfer mechanism proposed follows TiO2 conduction band electrons are responsible for the reduction of selenate to elemental Se (Se0) and both carbon dioxide radicals (CO2·-) and Se conduction band electrons are responsible for the further reduction of Se0 to hydrogen selenide (H2Se).

Real-time monitoring of nanoscale TiO2 concentration by spectrophotometry: implications of agglomeration due to natural organic matter and multivalent ions.

The study of the environmental fate of nanoscale TiO2 (n-TiO2) is a major recent research focus which requires a rapid and accurate on-site concentration determination method. Inductively coupled plasma mass spectroscopy (ICP-MS) has been the most widely used method for determining the concentration of n-TiO2 in environmental samples; however, poses many challenges, such as hazardous hydrofluoric acid pre-treatment and clear limitations in mobile on-site measurement and monitoring. This study demonstrates that industrial wastewater containing natural organic matter (NOM) can present a major challenge to the analysis of n-TiO2 by ICP-MS, and introduces a spectrophotometry technique that can be used as an alternative. The results suggest that spectrophotometry methods can be more accurate than slurry nebulization ICP-MS for measuring the concentrations of n-TiO2 in wastewater containing NOM under low salt conditions. Furthermore, this study demonstrates the use of a portable flow-through spectrophotometer for use in applications of wastewater treatment and environmental monitoring with real-time feedback of n-TiO2 concentrations. The ability to detect and monitor n-TiO2 will greatly assist in improving the understanding of hazards and risks that emerging nanomaterials pose to the environment and the public health.

Sensing Coated Iron-Oxide Nanoparticles with Spectral Induced Polarization (SIP): Experiments in Natural Sand Packed Flow-Through Columns.

The development of nanoparticle-based soil remediation techniques is hindered by the lack of accurate in situ nanoparticle (NP) monitoring and characterization methods. Spectral induced polarization (SIP), a noninvasive geophysical technique, offers a promising approach to detect and quantify NPs in porous media. However, its successful implementation as a monitoring tool requires an understanding of the polarization mechanisms, the governing NP-associated SIP responses and their dependence on the stabilizing coatings that are typically used for NPs deployed in environmental applications. Herein, we present SIP responses (0.1-10 000 Hz) measured during injection of a poloxamer-coated superparamagnetic iron-oxide nanoparticle (SPION) suspension in flow-through columns packed with natural sand from the Borden aquifer. An advective-dispersive transport model is fitted to outflow SPION concentration measurements to compute average concentrations over the SIP spatial response domain (within the columns). The average SPION concentrations are compared with the real and imaginary components of the complex conductivity. Excellent correspondence is found between the average SPION concentrations in the columns and the imaginary conductivity values, suggesting that NP-mediated polarization (that is, charge storage) increases proportionally with increasing SPION concentration. Our results support the possibility of SIP monitoring of spatial and temporal NP distributions, which can be immediately deployed in bench-scale studies with the prospect of future real-world field applications.

Evaluation of antiphospholipid antibody assays using latent class analysis to address the lack of a reference standard.

BACKGROUND: Method evaluation of new assays for the detection of antiphospholipid antibodies (aPL) such as anti-cardiolipin (aCL) or anti-ß2-glycoprotein I (aß2-GPI) is challenging, as no internationally accepted reference material is available yet. Besides a lack of standardization, unacceptable inter-laboratory comparability of established tests is regularly observed. Owing to the absence of a commonly accepted reference standard, the evaluation of two research surface plasmon resonance (SPR) biosensor assays was performed using statistical methods from latent class analysis (LCA). METHODS: aCL and aß2-GPI IgG and IgM were measured in sera from 63 antiphospholipid syndrome patients, fulfilling the Sydney criteria, and in 34 healthy controls with four commercial assays. LCA was performed on the results and sera were assigned to the antibody-positive or antibody-negative group. Sera were subsequently evaluated in the SPR assays for aCL and aß2-GPI. Optimal cutoffs and diagnostic performances of the research systems were established employing the LCA-derived gold standard. RESULTS: With area under the curve results of 0.96 and 0.89 for the detection of aCL and aß2-GPI, the research SPR assays discriminated well between antibody-positive and antibody-negative sera. Their sensitivities and specificities were comparable to the investigated commercial immunoassays. CONCLUSIONS: SPR assays are a suitable tool for the detection of aCL and aß2-GPI with diagnostic performances not different from currently available commercial tests. LCA enabled the calculation of sensitivities and specificities for aPL assays in absence of a reference standard.

Synthesis of an inositol hexakisphosphate (IP6) affinity probe to study the interactome from a colon cancer cell line.

Inositol hexakisphosphate (InsP6 or IP6) is an important signalling molecule in vesicular trafficking, neurotransmission, immune responses, regulation of protein kinases and phosphatases, activation of ion channels, antioxidant functions and anticancer activities. An IP6 probe was synthesised from myo-inositol via a derivatised analogue, which was immobilised through a terminal amino group onto Dynabeads. Systematic analysis of the IP6 interactome has been performed using the IP6 affinity probe using cytosolic extracts from the LIM1215 colonic carcinoma cell line. LC/MS/MS analysis identified 77 proteins or protein complexes that bind to IP6 specifically, including AP-2 complex proteins and ß-arrestins as well as a number of novel potential IP6 interacting proteins. Bioinformatic enrichment analysis of the IP6 interactome reinforced the concept that IP6 regulates a number of biological processes including cell cycle and division, signal transduction, intracellular protein transport, vesicle-mediated transport and RNA splicing.

Medium-Ring Effects on the Endo/Exo Selectivity of the Organocatalytic Intramolecular Diels-Alder Reaction.

The intramolecular Diels-Alder reaction has been used as a powerful method to access the tricyclic core of the eunicellin natural products from a number of 9-membered-ring precursors. The endo/exo selectivity of this reaction can be controlled through a remarkable organocatalytic approach, employing MacMillan's imidazolidinone catalysts, although the mechanistic origin of this selectivity remains unclear. We present a combined experimental and density functional theory investigation, providing insight into the effects of medium-ring constraints on the organocatalyzed intramolecular Diels-Alder reaction to form the isobenzofuran core of the eunicellins.

Ultrafast Fabrication of Flexible Dye-Sensitized Solar Cells by Ultrasonic Spray-Coating Technology.

This study investigates novel deposition techniques for the preparation of TiO2 electrodes for use in flexible dye-sensitized solar cells. These proposed new methods, namely pre-dye-coating and codeposition ultrasonic spraying, eliminate the conventional need for time-consuming processes such as dye soaking and high-temperature sintering. Power conversion efficiencies of over 4.0% were achieved with electrodes prepared on flexible polymer substrates using this new deposition technology and N719 dye as a sensitizer.

Chemically Altering the Solubility and Durability of Dyes for Sensitized Solar Cells.

By designing dyes with fluoroalkyl groups, the optical and electronic properties of the alkyl analogue were maintained while dramatically altering the solubility. Dyes, F-TABTA (8) and its masked derivative F-TABTSi (9), that enable them to be deposited under conventional organic solvent and scCO2 conditions, respectively, were developed. In liquid DSSC devices, the fluoroalkyl dye (F-TABTA, 8) performs slightly better than its alkyl analogue (D21L6, 10), and interestingly, it was found that the former device showed better stability over time. Deploying the silyl-masked precursor F-TABTSi (9), this dye was deposited onto TiO2 photoanodes from scCO2 in very short contact times (2.5 h), and ECEs of 7.70% were obtained that exceed the performance of the alkyl dye when deposited by conventional methods.

Organic Photovoltaic Materials--Design, Synthesis and Scale-Up.

This account describes the work of our group in the area of organic photovoltaics in the past six years. The emphasis is on our experiences in the development of the organic materials, their characterization, scale-up and application in devices. We share our insight into the relationship between synthetic methods, molecular properties, bulk material properties and device performance.

Plasmodium falciparum coronin organizes arrays of parallel actin filaments potentially guiding directional motility in invasive malaria parasites.

BACKGROUND: Gliding motility in Plasmodium parasites, the aetiological agents of malaria disease, is mediated by an actomyosin motor anchored in the outer pellicle of the motile cell. Effective motility is dependent on a parasite myosin motor and turnover of dynamic parasite actin filaments. To date, however, the basis for directional motility is not known. Whilst myosin is very likely orientated as a result of its anchorage within the parasite, how actin filaments are orientated to facilitate directional force generation remains unexplained. In addition, recent evidence has questioned the linkage between actin filaments and secreted surface antigens leaving the way by which motor force is transmitted to the extracellular milieu unknown. Malaria parasites possess a markedly reduced repertoire of actin regulators, among which few are predicted to interact with filamentous (F)-actin directly. One of these, PF3D7_1251200, shows strong homology to the coronin family of actin-filament binding proteins, herein referred to as PfCoronin. METHODS: Here the N terminal beta propeller domain of PfCoronin (PfCor-N) was expressed to assess its ability to bind and bundle pre-formed actin filaments by sedimentation assay, total internal reflection fluorescence (TIRF) microscopy and confocal imaging as well as to explore its ability to bind phospholipids. In parallel a tagged PfCoronin line in Plasmodium falciparum was generated to determine the cellular localization of the protein during asexual parasite development and blood-stage merozoite invasion. RESULTS: A combination of biochemical approaches demonstrated that the N-terminal beta-propeller domain of PfCoronin is capable of binding F-actin and facilitating formation of parallel filament bundles. In parasites, PfCoronin is expressed late in the asexual lifecycle and localizes to the pellicle region of invasive merozoites before and during erythrocyte entry. PfCoronin also associates strongly with membranes within the cell, likely mediated by interactions with phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2) at the plasma membrane. CONCLUSIONS: These data suggest PfCoronin may fulfil a key role as the critical determinant of actin filament organization in the Plasmodium cell. This raises the possibility that macro-molecular organization of actin mediates directional motility in gliding parasites.

A molecular nematic liquid crystalline material for high-performance organic photovoltaics.

Solution-processed organic photovoltaic cells (OPVs) hold great promise to enable roll-to-roll printing of environmentally friendly, mechanically flexible and cost-effective photovoltaic devices. Nevertheless, many high-performing systems show best power conversion efficiencies (PCEs) with a thin active layer (thickness is ~100 nm) that is difficult to translate to roll-to-roll processing with high reproducibility. Here we report a new molecular donor, benzodithiophene terthiophene rhodanine (BTR), which exhibits good processability, nematic liquid crystalline behaviour and excellent optoelectronic properties. A maximum PCE of 9.3% is achieved under AM 1.5G solar irradiation, with fill factor reaching 77%, rarely achieved in solution-processed OPVs. Particularly promising is the fact that BTR-based devices with active layer thicknesses up to 400 nm can still afford high fill factor of ~70% and high PCE of ~8%. Together, the results suggest, with better device architectures for longer device lifetime, BTR is an ideal candidate for mass production of OPVs.

Organic solar cells using a high-molecular-weight benzodithiophene-benzothiadiazole copolymer with an efficiency of 9.4%.

A high molecular weight donor-acceptor conjugated polymer is synthesized using the Suzuki polycondensation method. Using this polymer, a single-junction bulk-heterojunction solar cell is fabricated giving a power conversion efficiency of 9.4% using a fullerene-modified ZnO interlayer at the cathode contact.

Development of a new parallelized, optical biosensor platform for label-free detection of autoimmunity-related antibodies.

Autoimmune diseases are characterized by the presence of autoantibodies in serum of affected patients. The heterogeneity of autoimmune relevant antigens creates a variety of different antibodies, which requires a simultaneous detection mode. For this reason, we developed a tool for parallelized, label-free, optical detection that accomplishes the characterization of multiple antigen-antibody interactions within a single measurement on a timescale of minutes. Using 11-aminoundecyltrimethoxysilane, we were able to immobilize proteinogenic antigens as well as an amino-functionalized cardiolipin on a glass surface. Assay conditions were optimized for serum measurements with a single spot antigen chip on a single spot 1-λ detection system. Minimized background signal allows a differentiation between patients and healthy controls with a good sensitivity and specificity. Applying polarized imaging reflectometric interference spectroscopy, we evaluated samples from three APS patients and three control subjects for this proof-of-principle and already obtained good results for ß2-glycoprotein I and cardiolipin.

Photophysics and aggregation effects of a triphenylamine-based dye sensitizer on metal-oxide nanoparticles suspended in an ion trap.

The photophysical behaviour of a triphenylamine-based organic dye sensitizer (Carbz-PAHTDTT) attached to alumina and titania nanoparticles (labelled Carbz-Al and Carbz-Ti, respectively) is examined in the absence and presence of the chenodeoxycholic acid (CDCA) coadsorber. The experiments are conducted in vacuo by suspending the target dye-sensitized nanoparticles within a quadrupole ion trap, where they are probed with laser radiation to obtain emission spectra and time-resolved excited state decay curves. For Carbz-Al, the dye's emission band is blue-shifted and the excited state lifetime is increased upon the coabsorption of CDCA, effects attributed to reduced dye aggregation. Compared to Carbz-Al, the Carbz-Ti excited state lifetimes are significantly shorter due to excited dye molecules injecting electrons into the titania conduction band. For Carbz-Ti, the electron injection quantum yields for the surfaces with CDCA (CDCA : dye = 25 : 1) and without CDCA are estimated to be 0.87 and 0.71, respectively. The gas-phase results demonstrate that Carbz-PAHTDTT dye aggregates are detrimental to the performance of a dye-sensitized solar cell.

Enhancement of efficiency in organic photovoltaic devices containing self-complementary hydrogen-bonding domains.

Self-complementary hydrogen-bonding domains were incorporated as the electron deficient unit in "push-pull", p-type small molecules for organic photovoltaic active layers. Such compounds were found to enhance the fill factor, compared with similar non-self-organized compounds reported in the literature, leading to higher device efficiencies. Evidence is presented that the ability of these molecules to form one-dimensional hydrogen-bonded chains and subsequently exhibit hierarchical self-assembly into nanostructured domains can be correlated with improved device efficiency.

Enhanced photovoltaic efficiency via light-triggered self-assembly.

Light-initiated, radical and hydrogen-bond induced self-assembly of bis-acetamido-functionalized triarylamines is demonstrated to occur in strongly dipolar "push-pull" molecules. This self-assembly process results in the formation of self-assembled nanostructures which in turn increase the efficiency of organic photovoltaic devices.

The PI(3)P interactome from a colon cancer cell.

A comprehensive analysis of the phosphoinositide interactome has been performed using an ω-amino analogue of phosphatidylinositol 3-phosphate (PI(3)P immobilised onto Affi-10 beads for use as an affinity absorbent for cytosolic, membrane and nuclear extracts from the LIM1215 colonic carcinoma cell line. Affinity/LC/MS/MS experiments allowed the identification of 681 proteins/protein complexes which interact with PI(3)P. Protein domain enrichment analysis identified proteins possessing PI(3)P (e.g., FYVE, PX, PH), PIP and PIP/phospholipid binding domains along with small GTPases, GTPase regulators, kinases and SH2/SH3 containing proteins. Functional and pathway enrichment analyses highlighted the major role of PI(3)P in endocytosis dynamics and vesicular trafficking, intracellular cell signalling regulation, cell division and cytokinesis. BIOLOGICAL SIGNIFICANCE: This study provides an initial detailed assessment of the phosphatidylinositol 3-phosphate (PI(3)P) interactome, highlights the major role of PI(3)P in endocytosis dynamics and vesicular trafficking, cell intracellular regulation, signalling and cytokinesis and suggests potential PI(3)P specificity for further biochemical and biological characterisation.

Covalent attachment of functionalized cardiolipin on a biosensor gold surface allows repetitive measurements of anticardiolipin antibodies in serum.

Antiphospholipid antibodies (aPL) are a relevant serological indicator of antiphospholipid syndrome (APS). A solid-state surface with covalently bound ω-amine-functionalized cardiolipin was established and the binding of ß2-glycoprotein I (ß2-GPI) was investigated either by use of surface plasmon resonance (SPR) biosensor, by electrically switchable DNA interfaces (switchSENSE) and by scanning tunneling microscopy (STM). STM could clearly visualize the attachment of ß2-GPI to the cardiolipin surface. Using the switchSENSE sensor, ß2-GPI as specific ligand could be identified by increased hydrodynamic friction. The binding of anti-cardiolipin antibodies (aCL) was detected against the ω-amine-functionalized cardiolipin-modified SPR biosensor (aCL biosensor) using sera from healthy donors, APS patients and syphilis patients. Our results showed that the aCL biosensor is a much more sensitive diagnostic device for APS patients compared to previous methods. The specificity between ß2-GPI-dependent autoimmune- and ß2-GPI-independent infection-associated types of aPLs was also studied and they can be distinguished by the different binding kinetics and patterns.

Intramolecular nitrone dipolar cycloadditions: control of regioselectivity and synthesis of naturally-occurring spirocyclic alkaloids.

The intramolecular nitrone dipolar cycloaddition of in situ-generated nitrones such as compound 26 has been used for the synthesis of cyclic isoxazolidines 27 and 29. The regioselectivity of the intramolecular cycloaddition depends on the nature of the terminal substituent on the dipolarophile. The influence of the substituent on the regioselectivity of the cycloaddition has been examined using several model systems and two methods of nitrone formation. These studies demonstrated that the cyano-substituent plays a special role in favouring the formation of the 6,6,5-ring fused adduct 27 under thermodynamically controlled conditions. The utility of the cyclo-adduct 57 (see Scheme 12) as a precursor for the naturally occurring histrionicotoxins is illustrated by the synthesis of three "unsymmetrical" (i.e. with each side chain bearing different functional groups) members of the histrionicotoxin family HTX-259A, HTX-285C and HTX-285E (2, 3 and 4 respectively).

Causation in a cascade: the origins of selectivities in intramolecular nitrone cycloadditions.

The factors controlling chemo-, regio-, and stereoselectivity in a cascade of reactions starting from a bis(cyanoalkenyl)oxime and proceeding via nitrone cycloadditions have been unraveled through a series of density functional theory calculations with several different functionals. Both kinetic and thermodynamic control of the reaction cascade are important, depending upon the conditions. Kinetic control was analyzed by the distortion/interaction model and found to be dictated by differences in distortions of the cycloaddends in the transition states. A new mechanism competing with that originally proposed in the application of these reactions to the histrionicotoxin synthesis was discovered in these studies.