Solvent dependence of the one-electron reduction of substituted benzo- and naphthoquinones

Potentials for the one-electron reduction of a series of substituted benzo- and naphthoquinones were measured in 10 aprotic solvents by cyclic voltammetry and used to construct Hammett plots. Hammett reaction constants, ρ, were determined in each solvent and used as indicators of the solvent-mediated stabilization of the charged radical-anion product of the reduction reaction. Correlations of Hammett ρ values with solvent parameters suggest that the Lewis acidity of the solvent, in particular the solvent's ability to donate a partially positive proton, is a consistent predictor of the degree of charge stabilization of the quinone radical anion. Other mechanisms of charge stabilization, including solvent–solute charge transfer complexes and dipole–dipole interactions involving the molecular dipole moment (or an induced dipole moment) of the solvent, were found to be inconsistent predictors of the effect of solvent on one-electron quinone reduction in aprotic media.     

The Walkerton tragedy --issues for water quality monitoring

One of the most significant weaknesses in modern day water quality management is the detection of microbiological indicators. Microbial tests are normally conducted off-site, often resulting in long turn-around time, risk of contamination, cross contamination and adulteration. Here Stephen Brown and Moe Hussain present a thought provoking case study where limitations in current analytical technologies for water monitoring had fatal results and discuss new approaches to microbiological monitoring that might prevent similar disasters occurring in the future.     

Hyperfine structure determination of the 72D52state of 133Cs

The magnitude and sign of the hyperfine structure of $\text{7}{}^2\text{D}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$state of ¹³³Cs have been measured. We find the magnetic dipole coupling constant to be A = -1.7 (2) MHz.     

B-transform and its application to a fish-hyacinth model

A new transform proposed by Oyelami and Ale for impulsive systems is applied to an impulsive fish-hyacinth model. A biological policy regarding the growth of the fish and the hyacinth populations is formulated.     

Design and concise synthesis of a novel type of green fluorescent protein chromophore analogue

A small molecular model compound for the green fluorescent protein chromophore was readily synthesized by a novel condensation reaction of (thio)imidate with imino-ester via an aziridine intermediate. This compound showed fluorescence in the solid and frozen solution states but not in the solution state. Its fluorescent property was successfully applied in the detection of dsDNA.     

Effects of lipopolysaccharide-induced inflammation on expression of growth-associated genes by corticospinal neurons

Background  

Inflammation around cell bodies of primary sensory neurons and retinal ganglion cells enhances expression of neuronal growth-associated genes and stimulates axonal regeneration. We have asked if inflammation would have similar effects on corticospinal neurons, which normally show little response to spinal cord injury. Lipopolysaccharide (LPS) was applied onto the pial surface of the motor cortex of adult rats with or without concomitant injury of the corticospinal tract at C4. Inflammation around corticospinal tract cell bodies in the motor cortex was assessed by immunohistochemistry for OX42 (a microglia and macrophage marker). Expression of growth-associated genes c-jun, ATF3, SCG10 and GAP-43 was investigated by immunohistochemistry or in situ hybridisation.     

On the number of cusps on cuspidal curves on Hirzebruch surfaces

In this article we give an upper bound for the number of cusps on a cuspidal curve on a Hirzebruch surface. We adapt the results that have been found for a similar question asked for cuspidal curves on the projective plane, and restate the results in this new setting.     

Real-time cell-microelectronic sensing of nanoparticle-induced cytotoxic effects

We report a real-time cell analysis (RTCA) sensing method of 96 electronic microwells for profiling the cytotoxicity of nanoparticles on different cell lines. The method consists of 96 microwells embedded with microelectrodes (96x E-plate) to measure impedance changes of adherent cell lines. When the testing cells change in population, adhesion, and/or morphology, the impedance at the cell–electrode interface changes to provide real-time monitoring of overall cell status. To demonstrate this technique, we used three cell lines as sensing probes: two human lung carcinoma cell lines, A549 and SK-MES-1, and a normal mammalian cell line, CHO-K1. We tested two well-characterized nanoparticles: nano-titanium dioxide (nTiO₂) and nano-silver (nAg). The three cell lines were separately seeded into 96x E-plates and treated with varying concentrations of nanoparticles (0.078–160 μg mL⁻¹). This method provides dynamic cell response profiles and temporal IC₅₀ histograms, showing concentration-, time-, particle-, and cell-dependent cytotoxicity. The 24 h and 48 h IC₅₀ values of nAg obtained using both the RTCA and the neutral red uptake (NRU) assays were in good agreement, validating the RTCA technique. The RTCA assay does not suffer interference from nTiO₂, whereas the NRU assay cannot be used due to severe interference from nTiO₂. A cytostatic response was observed in CHO-K1 cells after 24 h exposure to 40 μg mL⁻¹ nTiO₂, which was correlated with S-phase cell cycle arrest based on cell cycle analysis using flow cytometry. This suggests that the shapes of the response curves provide indicative information, directing further studies into the mode of action of the toxicant. Advantages of the RTCA technique over traditional colorimetric assays for screening the cytotoxicity of nanoparticles include minimizing interference, qualitative and quantitative cytotoxicity data, and the capability of real-time and high-throughput measurements.