- Water body type and group size affect the flight initiation distance of European waterbirds. [Journal Article]
- PlosPLoS One 2019; 14(7):e0219845
- Human encroachment on nature grows constantly, increasing human-wildlife interactions. Flight initiation distance (FID, the distance at which animals flee from an approaching threat) is often used to…
Human encroachment on nature grows constantly, increasing human-wildlife interactions. Flight initiation distance (FID, the distance at which animals flee from an approaching threat) is often used to measure antipredator behaviour and establish buffer zones to reduce human impact on wildlife. In this study, we approached 10 waterbird species on larger lakes and narrower rivers using a motorboat. We investigated whether water body type, season (winter/spring), approach starting distance, species body mass, and group size influenced bird FID. Average bird FID was 145 ± 92 m and differed between species. In general, FID of all species was larger on lakes than rivers and increased with increasing group size and approach starting distance. When analysed separately for the two most common species, common goldeneyes (Bucephala clangula) and mallards (Anas platyrhynchos), FID increased with increasing starting distance on rivers, but not lakes, likely because birds on lakes have enough time to evaluate the approaching object and take flight at great distance. Additionally, birds might perform different activities on lakes versus rivers, leading to varying energetic trade-offs between the two habitat types, which may affect the decision when to take flight. Finally, mallards aggregated in larger groups on lakes, which affected FID, likely due to enhanced visibility (i.e., earlier detection of the approaching boat) and detection probability (via increased group size) on lakes. Our results emphasize the importance of accounting for habitat characteristics, such as water body type, when studying waterbird FID, because they can affect the visibility of stimuli, group size and potentially animal behaviour, factors which should be taken into account when planning buffer zones for waterbirds in conservation areas.
- Dark-Field Microwells toward High-Throughput Direct miRNA Sensing with Gold Nanoparticles. [Journal Article]
- ASACS Sens 2019 Jul 16
- MicroRNA (miRNA) is a class of short RNA that is emerging as an ideal biomarker, as its expression level has been found to correlate with different types of diseases including diabetes and cancer. Th…
MicroRNA (miRNA) is a class of short RNA that is emerging as an ideal biomarker, as its expression level has been found to correlate with different types of diseases including diabetes and cancer. The detection of miRNA is highly beneficial for early diagnostics and disease monitoring. However, miRNA sensing remains difficult because of its small size and low expression levels. Common techniques such as quantitative real-time polymerase chain reaction (qRT-PCR), in situ hybridization and Northern blotting have been developed to quantify miRNA in a given sample. Nevertheless, these methods face common challenges in point-of-care practice as they either require complicated sample handling and expensive equipment, or suffer from low sensitivity. Here we present a new tool based on dark-field microwells to overcome these challenges in miRNA sensing. This miniaturized device enables the readout of a gold nanoparticle assay without the need of a dark-field microscope. We demonstrate the feasibility of the dark-field microwells to detect miRNA in both buffer solution and cell lysate. The dark-field microwells allow affordable miRNA sensing at a high throughput which make them a promising tool for point-of-care diagnostics.
- Mutational loss of carotenoids in alkaliphilic Bacillus pseudofirmus OF4 results in sensitivity to oxidative stress and growth at high pH. [Journal Article]
- MMicrobiology 2019 Jul 15
- Alkaliphilic Bacillus pseudofirmus OF4, which has a broad pH growth range of 7.5 to above 10.5, is yellow-pigmented due to carotenoids. Carotenoids contribute to membrane rigidity and can alleviate c…
Alkaliphilic Bacillus pseudofirmus OF4, which has a broad pH growth range of 7.5 to above 10.5, is yellow-pigmented due to carotenoids. Carotenoids contribute to membrane rigidity and can alleviate cellular oxidative stress. This study was undertaken to gain insight into the roles carotenoids play in alkaliphile physiology. Carotenoid content was high in stationary phase and in cells grown nonfermentatively at pH 10.5 A colourless mutant was isolated by the in-frame deletion of a key carotenogenic gene, crtM. In cells grown to stationary phase in a pH 10.5 medium with a suboptimal concentration of Na+, the ∆crtM strain exhibited lower resistance to paraquat and hydrogen peroxide. Preincubation of the mutant in a nutrient-free pH 10.5 buffer revealed a pronounced sensitivity to hydrogen peroxide in growth at pH 7.5. In growth curves in media with optimal or suboptimal nutrient concentrations conducted at 37°, the mutant grew identically to the wild-type at pH 7.5 but its lag time was longer than the wild-type at pH 10.5 and growth was slower when the carbon source, malate, was limiting. When the temperature of the growth curves was lowered to 25°, the mutant no longer had a pH 10.5 phenotype, implicating the effect of carotenoids on membrane rigidity for the pH 10.5 growth phenotype. These results suggest that carotenoids in B. pseudofirmus OF4 play a role in managing oxidative stress when cells are adapting to other stressful conditions such as nutrient limitation while also helping to maintain membrane fluidity/rigidity balance for membrane-linked functions.
- Separation of antipyretic analgesics by open tubular capillary electrochromatography with homopolymer coatings. [Journal Article]
- JSJ Sep Sci 2019 Jul 16
- This study developed an open-tubular capillary electrochromatography protocol for the analysis of antipyretic analgesics drugs, which used a multifunctional homopolymer as coatings. A controlled/livi…
This study developed an open-tubular capillary electrochromatography protocol for the analysis of antipyretic analgesics drugs, which used a multifunctional homopolymer as coatings. A controlled/living radical polymerization strategy was adopted to obtain poly(N-acryloxysuccinimide) with a tunable chain-length. The homopolymer coating enhanced the separation performance by contributing to the hydrophobic and hydrogen-bonding interactions between the analytes and the homopolymer. The effect of polymer chain-length and buffer pH and concentration on the separation efficiency were evaluated. In this approach, baseline separation of the three test drugs was achieved within 15 minutes. The repeatability of the prepared homopolymer coating was investigated, with the relative standard deviations < 2.88% observed in intra-day and inter-day runs. Good linearity in the 5.0-800.0 µM range (R2 ≥ 0.998) demonstrates that accurate quantitative analysis of real samples was achieved. Moreover, the proposed assay was used to quantify the three drugs (aminopyrine, 4-aminoantipyrine and phenacetin) in urine samples, achieving recovery rates between 92.1% and 108.7%. This promising methodology may be used for the analysis of drugs in real bio-samples and for the development of unique homopolymer coatings for open-tubular capillary electrochromatography systems. This article is protected by copyright. All rights reserved.
- HYDROXYLAMINE OXIDATION ON POLYCRYSTALLINE GOLD ELECTRODES IN AQUEOUS ELECTROLYTES: QUANTITATIVE ON-LINE MASS SPECTROMETRY UNDER FORCED CONVECTION. [Journal Article]
- CChemphyschem 2019 Jul 16
- A method is herein presented that allows quantitative determination of faradaic efficiencies for dinitrogen, N2, generation, during the electrochemical oxidation of hydroxylamine, NH2OH, on a polycry…
A method is herein presented that allows quantitative determination of faradaic efficiencies for dinitrogen, N2, generation, during the electrochemical oxidation of hydroxylamine, NH2OH, on a polycrystalline, Au(poly), gold disk electrode in aqueous electrolytes over a wide pH range. This tactic involves the use of an impinging jet electrolyte configuration incorporating a gas porous ring connected in turn to a mass spectrometer. The actual amount of N2 generated at the Au(poly) disk was assayed using the oxidation of hydrazine, N2H4, in aqueous phosphate buffer (pH 7). This redox process yields N2 as the only product, allowing a direct correlation to be established between the changes in the partial pressures of N2 and the current flowing through the disk electrode. An analysis of the data collected revealed a strong dependence of faradaic efficiencies both on pH and the applied potential. Although faradaic efficiencies as high as 20 to 30% were found in acid and neutral media over a narrow potential region, those in alkaline solution were far smaller in the entire range examined.
- Tuning Redox Active Polyoxometalates for Efficient Electron-coupled Proton Buffer Mediated Water Splitting. [Journal Article]
- CChemistry 2019 Jul 16
- We present a strategy to tune the redox properties of polyoxometalate clusters to enhance the electron-coupled proton buffer-mediated water splitting process. By substituting the heteroatom template …
We present a strategy to tune the redox properties of polyoxometalate clusters to enhance the electron-coupled proton buffer-mediated water splitting process. By substituting the heteroatom template in the Keggin-type [H8-mXmW12O40] polyoxometalate cluster from Silicon(IV) to Zinc(II), it is possible to double number of redox electrons and protonation from two to four. This increase can be achieved via control of the redox potentials as controlled by the oxidation state of the heteroion, allowing an increase in electron storage from H3PW12O40 (2e) and H4SiW12O40 (2e) to H6ZnW12O40 (4e). This means that H6ZnW12O40 can act as a high-performance redox mediator in an electrolytic cell for the on-demand generation of hydrogen with a high decoupling efficiency of 95.5% and an energy efficiency of 83.3%. Furthermore, the H6ZnW12O40 cluster also exhibits excellent cycling characteristics and redox reversibility with almost 100% retention of capacity for the production of hydrogen over 200 cycles with a high coulombic efficiency > 92% per cycle at 30 mA/cm2.
- Strain-stress study of AlxGa1-xN/AlN heterostructures on c-plane sapphire and related optical properties. [Journal Article]
- SRSci Rep 2019 Jul 15; 9(1):10172
- This work presents a systematic study of stress and strain of AlxGa1-xN/AlN with composition ranging from GaN to AlN, grown on a c-plane sapphire by metal-organic chemical vapor deposition, using syn…
This work presents a systematic study of stress and strain of AlxGa1-xN/AlN with composition ranging from GaN to AlN, grown on a c-plane sapphire by metal-organic chemical vapor deposition, using synchrotron radiation high-resolution X-ray diffraction and reciprocal space mapping. The c-plane of the AlxGa1-xN epitaxial layers exhibits compressive strain, while the a-plane exhibits tensile strain. The biaxial stress and strain are found to increase with increasing Al composition, although the lattice mismatch between the AlxGa1-xN and the buffer layer AlN gets smaller. A reduction in the lateral coherence lengths and an increase in the edge and screw dislocations are seen as the AlxGa1-xN composition is varied from GaN to AlN, exhibiting a clear dependence of the crystal properties of AlxGa1-xN on the Al content. The bandgap of the epitaxial layers is slightly lower than predicted value due to a larger tensile strain effect on the a-axis compared to the compressive strain on the c-axis. Raman characteristics of the AlxGa1-xN samples exhibit a shift in the phonon peaks with the Al composition. The effect of strain on the optical phonon energies of the epitaxial layers is also discussed.
- Cytosolic Ca2+ Buffers Are Inherently Ca2+ Signal Modulators. [Journal Article]
- CSCold Spring Harb Perspect Biol 2019 Jul 15
- For precisely regulating intracellular Ca2+ signals in a time- and space-dependent manner, cells make use of various components of the "Ca2+ signaling toolkit," including Ca2+ entry and Ca2+ extrusio…
For precisely regulating intracellular Ca2+ signals in a time- and space-dependent manner, cells make use of various components of the "Ca2+ signaling toolkit," including Ca2+ entry and Ca2+ extrusion systems. A class of cytosolic Ca2+-binding proteins termed Ca2+ buffers serves as modulators of such, mostly short-lived Ca2+ signals. Prototypical Ca2+ buffers include parvalbumins (α and β isoforms), calbindin-D9k, calbindin-D28k, and calretinin. Although initially considered to function as pure Ca2+ buffers, that is, as intracellular Ca2+ signal modulators controlling the shape (amplitude, decay, spread) of Ca2+ signals, evidence has accumulated that calbindin-D28k and calretinin have additional Ca2+ sensor functions. These other functions are brought about by direct interactions with target proteins, thereby modulating their targets' function/activity. Dysregulation of Ca2+ buffer expression is associated with several neurologic/neurodevelopmental disorders including autism spectrum disorder (ASD) and schizophrenia. In some cases, the presence of these proteins is presumed to confer a neuroprotective effect, as evidenced in animal models of Parkinson's or Alzheimer's disease.
- Correlation analysis based on the hydropathy properties of non-steroidal anti-inflammatory drugs in solid-phase extraction (SPE) and reversed-phase high performance liquid chromatography (HPLC) with photodiode array detection and their applications to biological samples. [Journal Article]
- JCJ Chromatogr A 2019 Jul 06; :360351
- In the present work we analyzed the hydrophobicity and hydrophilicity properties of several non-steroidal anti-inflammatory drugs (NSAIDs) by investigating the structural changes of the dynamic hydro…
In the present work we analyzed the hydrophobicity and hydrophilicity properties of several non-steroidal anti-inflammatory drugs (NSAIDs) by investigating the structural changes of the dynamic hydrogen bond network in order to predict the extraction recovery of NSAIDs from biological fluids set by solid phase extraction (SPE). This work allows investigating the relationship between theoretical descriptors and experimental data using a parameter free method with a strong correlation (Pearson correlation 0.95, p-value 0.0003). The identification and quantification of analytes in human plasma were carried out by high performance liquid chromatography coupled with photodiode array detection (HPLC-PDA) using a Kinetex Evo C18 (150 x 4.6 mm I.D) protected by a guard column and a mixture of acetonitrile and 10 mM phosphate buffer (pH 2.5) (50:50, v/v) as mobile phase at isocratic conditions. Accuracy (BIAS%) ranged within -2.33% and + 8.05% while precision (RSD%) was less than 5.73%.The mean extraction recovery of the carprofen (IS) was 84.1% and the recovery of NSAIDs from human plasma ranged between 81.9% to 86.6%. LODs and LOQs for all the investigated NSAIDs were 0.003 and 0.01 μg/mL, respectively. The method was validated according to the ICH guide line in the range 0.010-20.0 μg/mL.
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- Highly sensitive and selective electrochemical paper-based device using a graphite screen-printed electrode modified with molecularly imprinted polymers coated Fe3O4@Au@SiO2 for serotonin determination. [Journal Article]
- ACAnal Chim Acta 2019 Oct 24; 1077:255-265
- Herein, we propose a highly sensitive and selective three-dimensional electrochemical paper-based analytical device (3D-ePAD) to determine serotonin (Ser). It uses a graphite-paste electrode modified…
Herein, we propose a highly sensitive and selective three-dimensional electrochemical paper-based analytical device (3D-ePAD) to determine serotonin (Ser). It uses a graphite-paste electrode modified with nanoparticles coated with molecularly imprinted polymer (MIP). Fe3O4@Au nanoparticles were encapsulated with silica to create novel nano-sized MIP. Morphology and structural characterization reveal that silica imprinted sites (Fe3O4@Au@SiO2) synthesized via sol-gel methods provide excellent features for Ser detection, including high porosity, and greatly improve analyte diffusion and adsorption to provide a faster response by the MIP sensor. The template molecule was effectively removed by solvent extraction to provide a greater number of specific cavities that enhance analyte capacity and sensitivity. The 3D-ePAD was fabricated by alkyl ketene dimer (AKD)-inkjet printing of a circular hydrophobic detection zone on filter paper for application of aqueous samples, coupled with screen-printed electrodes on the paper, which was folded underneath the hydrophobic zone. The sensor was constructed by drop coating of Fe3O4@Au@SiO2-MIP nanocomposites on the graphite electrode (GPE) surface. The MIP sensor (Fe3O4@Au@SiO2-MIP/GPE) was used in the detection of Ser by linear-sweep voltammetry (LSV) in 0.1 M phosphate buffer at pH 8.0. The device exhibits high sensitivity toward Ser, which we attribute to synergistic effects between catalytic properties, electrical conductivity of Fe3O4@Au@SiO2, and significantly increased numbers of imprinted sites. Ser oxidation was observed at +0.39 V. Anodic peak currents for Ser show linearity from 0.01 to 1000 μM (y = 0.0075 ± 0.0049 x + 0.4071 ± 0.0052, r2 = 0.993), with a detection limit of 0.002 μM (3S/N). The device provides good repeatability (%relative standard deviations; RSD) = 4.23%, calculated from the current responses of ten different MIP sensors). The device also exhibits high selectivity and reproducibility (%RSD = 8.35%, obtained from five calibration plots). The analytical performance of the device is suitable for the determination of Ser in pharmaceutical capsules and urine samples.