Design and development of a portable resistive sensor based on α-MnO2 /GQD nanocomposites for trace quantification of Pb(II) in water.

The occurrence of heavy metal ions in food chain is appearing to be a major problem for mankind. The traces of heavy metals, especially Pb(II) ions present in water bodies remains undetected, untreated, and it remains in the food cycle causing serious health hazards for human and livestock. The consumption of Pb(II) ions may lead to serious medical complications including multiple organ failure which can be fatal. The conventional methods of heavy metal detection are costly, time-consuming and require laboratory space. There is an immediate need to develop a cost-effective and portable sensing system which can easily be used by the common man without any technical knowhow. A portable resistive device with miniaturized electronics is developed with microfluidic well and α-MnO2 /GQD nanocomposites as a sensing material for the sensitive detection of Pb(II). α-MnO2 /GQD nanocomposites which can be easily integrated with the miniaturized electronics for real-time on-field applications. The proposed sensor exhibited a tremendous potential to be integrated with conventional water purification appliances (household and commercial) to give an indication of safety index for the drinking water. The developed portable sensor required low sample volume (200 µL) and was assessed within the Pb(II) concentration range of 0.001 nM to 1 uM. The Limit of Detection (LoD) and sensitivity was calculated to be 0.81 nM and 1.05 kΩ/nM/mm2 , and was validated with the commercial impedance analyser. The shelf-life of the portable sensor was found to be ∼45 days.

Rapid removal of lead(II) ions from water using iron oxide-tea waste nanocomposite - a kinetic study.

Lead (Pb) ions are a major concern to the environment and human health as they are contemplated cumulative poisons. In this study, facile synthesis of magnetic iron oxide-tea waste nanocomposite is reported for adsorptive removal of lead ions from aqueous solutions and easy magnetic separation of the adsorbent afterwards. The samples were characterised by scanning electron microscopy, Fourier transform-infrared spectroscopy, X-ray diffraction, and Braunner-Emmet-Teller nitrogen adsorption study. Adsorptive removal of Pb(II) ions from aqueous solution was followed by ultraviolet-visible (UV-Vis) spectrophotometry. About 95% Pb(II) ion removal is achieved with the magnetic tea waste within 10 min. A coefficient of regression R2 ≃ 0.99 and adsorption density of 18.83 mg g-1 was found when Pb(II) ions were removed from aqueous solution using magnetic tea waste. The removal of Pb(II) ions follows the pseudo-second-order rate kinetics. External mass transfer principally regulates the rate-limiting phenomena of adsorption of Pb(II) ions on iron oxide-tea waste surface. The results strongly imply that magnetic tea waste has promising potential as an economic and excellent adsorbent for the removal of Pb(II) from water.

Therapeutic strategies for the treatment of tauopathies: Hopes and challenges.

A group of neurodegenerative diseases referred to as tauopathies are characterized by the presence of brain cells harboring inclusions of pathological species of the tau protein. These disorders include Alzheimer's disease and frontotemporal lobar degeneration due to tau pathology, including progressive supranuclear palsy, corticobasal degeneration, and Pick's disease. Tau is normally a microtubule (MT)-associated protein that appears to play an important role in ensuring proper axonal transport, but in tauopathies tau becomes hyperphosphorylated and disengages from MTs, with consequent misfolding and deposition into inclusions that mainly affect neurons but also glia. A body of experimental evidence suggests that the development of tau inclusions leads to the neurodegeneration observed in tauopathies, and there is a growing interest in developing tau-directed therapeutic agents. The following review provides a summary of strategies under investigation for the potential treatment of tauopathies, highlighting both the promises and challenges associated with these various therapeutic approaches.

Transcriptomic Analysis of Drosophila Mushroom Body Neurons Lacking Amyloid-ß Precursor-Like Protein Activity.

The amyloid-ß protein precursor (AßPP) is subjected to sequential intramembrane proteolysis by α-, ß-, andγ-secretases, producing secreted amyloid-ß (Aß) peptides and a cytoplasmically released AßPP Intracellular Domain (AICD). AICD complexes with transcription factors in the nucleus, suggesting that this AßPP fragment serves as an active signaling effector that regulates downstream genes, although its nuclear targets are poorly defined. To further understand this potential signaling mechanism mediated by AßPP, we performed a transcriptomic identification of the Drosophila genome that is regulated by the fly AßPP orthologue in fly mushroom body neurons, which control learning- and memory-based behaviors. We find significant changes in expression of 245 genes, representing approximately 1.6% of the Drosophila genome, with the changes ranging from +6 fold to -40 fold. The largest class of responsive targets corresponds to non-protein coding genes and includes microRNAs that have been previously implicated in Alzheimer's disease pathophysiology. Several genes were identified in our Drosophila microarray analyses that have also emerged as putative AßPP targets in similar mammalian transcriptomic studies. Our results also indicate a role for AßPP in cellular pathways involving the regulation of Drosophila Casein Kinase II, mitochondrial oxidative phosphorylation, RNA processing, and innate immunity. Our findings provide insights into the intracellular events that are regulated by AßPP activity in healthy neurons and that might become dysregulated as a result of abnormal AßPP proteolysis in AD.

Spectrin tetramer formation is not required for viable development in Drosophila.

The dominant paradigm for spectrin function is that (αß)2-spectrin tetramers or higher order oligomers form membrane-associated two-dimensional networks in association with F-actin to reinforce the plasma membrane. Tetramerization is an essential event in such structures. We characterize the tetramerization interaction between α-spectrin and ß-spectrins in Drosophila. Wild-type α-spectrin binds to both ß- and ßH-chains with high affinity, resembling other non-erythroid spectrins. However, α-spec(R22S), a tetramerization site mutant homologous to the pathological α-spec(R28S) allele in humans, eliminates detectable binding to ß-spectrin and reduces binding to ßH-spectrin ∼1000-fold. Even though spectrins are essential proteins, α-spectrin(R22S) rescues α-spectrin mutants to adulthood with only minor phenotypes indicating that tetramerization, and thus conventional network formation, is not the essential function of non-erythroid spectrin. Our data provide the first rigorous test for the general requirement for tetramer-based non-erythroid spectrin networks throughout an organism and find that they have very limited roles, in direct contrast to the current paradigm.

Evaluating hypoxia during air travel in healthy infants.

Up to a third of ex-preterm infants flying near term exhibit pulse oxygen saturation (SpO2) of less than 85% during air travel. A hypoxia challenge test (HCT) is recommended to evaluate the requirement for in-flight supplemental O2. The validity of the HCT in healthy, term infants has not been reported. This study aimed to characterise the in-flight hypoxia response and the accuracy of the HCT to predict this response in healthy, term infants in the first year of life. Infants (n=24: (15 male)) underwent a HCT prior to commercial air travel during which parents monitored SpO2. Thirty-two flights were undertaken with six infants completing multiple flights. The median in-flight SpO2 nadir was 87% and significantly lower than the HCT SpO2 nadir (92%: p<0.001). Infants on seven flights recorded SpO2<85% with one infant recording a HCT with a SpO2 less than 85%. There was marked variability in the in-flight SpO2 in the six infants who undertook multiple flights, and for three of these infants, the SpO2 nadir was both above and below 85%. We report that in healthy term infants an in-flight SpO2 below 85% is common and can vary considerably between flights and that the HCT poorly predicts the risk of in-flight hypoxia (SpO2<85%). As it is common for healthy term infants to have SpO2 less than 85% during air travel further research is needed to clarify whether this is an appropriate cut-off in this age group.

Protein trafficking abnormalities in Drosophila tissues with impaired activity of the ZIP7 zinc transporter Catsup.

Developmental patterning requires the precise interplay of numerous intercellular signaling pathways to ensure that cells are properly specified during tissue formation and organogenesis. The spatiotemporal function of the Notch signaling pathway is strongly influenced by the biosynthesis and intracellular trafficking of signaling components. Receptors and ligands must be trafficked to the cell surface where they interact, and their subsequent endocytic internalization and endosomal trafficking is crucial for both signal propagation and its down-modulation. In a forward genetic screen for mutations that alter intracellular Notch receptor trafficking in Drosophila epithelial tissues, we recovered mutations that disrupt the Catsup gene, which encodes the Drosophila ortholog of the mammalian ZIP7 zinc transporter. Loss of Catsup function causes Notch to accumulate abnormally in the endoplasmic reticulum (ER) and Golgi compartments, resulting in impaired Notch signaling. In addition, Catsup mutant cells exhibit elevated ER stress, suggesting that impaired zinc homeostasis causes increased levels of misfolded proteins within the secretory compartment.

Annexin B9 binds to ß(H)-spectrin and is required for multivesicular body function in Drosophila.

The role of the cytoskeleton in protein trafficking is still being defined. Here, we describe a relationship between the small Ca(2+)-dependent membrane-binding protein Annexin B9 (AnxB9), apical ß(Heavy)-spectrin (ß(H)) and the multivesicular body (MVB) in Drosophila. AnxB9 binds to a subset of ß(H) spliceoforms, and loss of AnxB9 results in an increase in basolateral ß(H) and its appearance on cytoplasmic vesicles that overlap with the MVB markers Hrs, Vps16 and EPS15. Similar colocalizations are seen when ß(H)-positive endosomes are generated either by upregulation of ß(H) in pak mutants or through the expression of the dominant-negative version of ß(H). In common with other mutations disrupting the MVB, we also show that there is an accumulation of ubiquitylated proteins and elevated EGFR signaling in the absence of AnxB9 or ß(H). Loss of AnxB9 or ß(H) function also causes the redistribution of the DE-Cadherin (encoded by shotgun) to endosomal vesicles, suggesting a rationale for the previously documented destabilization of the zonula adherens in karst (which encodes ß(H)) mutants. Reduction of AnxB9 results in degradation of the apical-lateral boundary and the appearance of the basolateral proteins Coracle and Dlg on internal vesicles adjacent to ß(H). These results indicate that AnxB9 and ß(H) are intimately involved in endosomal trafficking to the MVB and play a role in maintaining high-fidelity segregation of the apical and lateral domains.

Towards a membrane proteome in Drosophila: a method for the isolation of plasma membrane.

BACKGROUND: The plasma membrane (PM) is a compartment of significant interest because cell surface proteins influence the way in which a cell interacts with its neighbours and its extracellular environment. However, PM is hard to isolate because of its low abundance. Aqueous two-phase affinity purification (2PAP), based on PEG/Dextran two-phase fractionation and lectin affinity for PM-derived microsomes, is an emerging method for the isolation of high purity plasma membranes from several vertebrate sources. In contrast, PM isolation techniques in important invertebrate genetic model systems, such as Drosophila melanogaster, have relied upon enrichment by density gradient centrifugation. To facilitate genetic investigation of activities contributing to the content of the PM sub-proteome, we sought to adapt 2PAP to this invertebrate model to provide a robust PM isolation technique for Drosophila. RESULTS: We show that 2PAP alone does not completely remove contaminating endoplasmic reticulum and mitochondrial membrane. However, a novel combination of density gradient centrifugation plus 2PAP results in a robust PM preparation. To demonstrate the utility of this technique we isolated PM from fly heads and successfully identified 432 proteins using MudPIT, of which 37% are integral membrane proteins from all compartments. Of the 432 proteins, 22% have been previously assigned to the PM compartment, and a further 34% are currently unassigned to any compartment and represent candidates for assignment to the PM. The remainder have previous assignments to other compartments. CONCLUSION: A combination of density gradient centrifugation and 2PAP results in a robust, high purity PM preparation from Drosophila, something neither technique can achieve on its own. This novel preparation should lay the groundwork for the proteomic investigation of the PM in different genetic backgrounds in Drosophila. Our results also identify two key steps in this procedure: The optimization of membrane partitioning in the PEG/Dextran mixture, and careful choice of the correct lectin for the affinity purification step in light of variations in bulk membrane lipid composition and glycosylation patterns respectively. This points the way for further adaptations into other systems.