Nanomolar detection of hydrogen peroxide at a new polynuclear cluster of tin pentacyanonitrosylferrate nanoparticle-modified carbon ceramic electrode

This work describes a new electrochemical sensor for hydrogen peroxide based on tin pentacyanonitrosylferrate (SnPCNF)-modified carbon ceramic electrode (CCE). The modified electrode was constructed by using a sol-gel technique involving two steps: construction of CCE containing metallic tin (Sn) powder and then electrochemical creation of SnPCNF film on the surface of CCE. The modified electrode was characterized by energy-dispersive X-ray, Fourier transform infrared, scanning electron microscopy, and cyclic voltammetry (CV) techniques. The charge transfer coefficient (α) and charge transfer rate constant (k_s) for the modifying film were calculated. The electrocatalytic activity of the modified electrode toward the reduction of hydrogen peroxide was studied by CV and chronoamperometry. A linear calibration curve was obtained over the hydrogen peroxide concentration range of 0.5 to 69.4 μM using a hydrodynamic amperometric technique. The limit of detection (for a signal-to-noise ratio of 3) and sensitivity were found to be 92 nM and 0.89 μA/μM, respectively. Furthermore, the diffusion coefficient of hydrogen peroxide (D) and catalytic rate constant (k_cat) were calculated.     

Photoproduction of hydrogen, nitrogenase and hydrogenase activities of free and immobilized whole cells of Rhodobacter sphaeroides O.U. 001

Abstract Photoproduction of hydrogen, nitrogenase activity (acetylene reduction) and hydrogenase activity (methylene blue dye reduction) were studied in free and alginate immobilized whole cells of a purple non-sulfur photosynthetic bacterium Rhodobacter sphaeroides O.U. 001. Four-fold increase in hydrogen production, two-fold increase in nitrogenase activity and 1.2-fold increase in the hydrogenase activity were observed in immobilized cells compared to free cells. Effect of various inhibitors (CO and C₂H₂) and electron donor (H₂) on the above three functions by free and immobilized cells has also been studied.     

Synthesis of alkali metal hexahydroaluminate complexes using dimethyl ether as a reaction medium

A novel method of preparation of hexahydroaluminate complexes M₃AlH₆ (M = Li, Na or K) from the corresponding alkali metal hydride and tetrahydroaluminate has been explored, using dimethyl ether (Me₂O) as a solvent at near-ambient temperatures. The results are compared with those obtained using a recently established mechanochemical approach. Characterization of the products by powder X-ray diffraction revealed M₃AlH₆ to be formed in high yield for M = Li and Na, but not for M = K. The attempted preparation of Li₂NaAlH₆ and Li₂KAlH₆ was unsuccessful.     

The Everyday Life Context of Increasing Energy Demands: Time Use Survey Data in a Decomposition Analysis

Industrial ecologists have modeled with precision the material foundations of industrial systems, but given less attention to the demand for products and the drivers of structural changes in these systems. This article suggests that time use data complement data on monetary expenditure and can be used to elucidate the everyday life context in which the changes in the economy take place. It builds upon the claim that goods are not direct sources of utility, but enter specific household activities as inputs. A second argument for the proposed approach is that it can be used to introduce and foster human agency in analyses of production systems. The article uses Finnish time use survey data, consumption expenditure data, and data on the sectoral energy intensities of financial output in the Finnish economy. First, a measure of the energy intensity of activities is derived by relating consumer time use and the required direct and indirect energy requirements. Second, the results include a decomposition of changes in the energy requirements of private consumption in Finland during the 1990s. It is shown that although the same activities on average require increasing energy inputs per unit of time, Finns have simultaneously changed the structure of their everyday life toward less energy-intensive activities.     

Arsenic Bioaccumulation in Freshwater Fishes

The arsenic ambient water quality criterion (AWQC) for protection of human health via ingestion of aquatic organisms is currently 0.14 μ g/L. This AWQC is derived using a bioconcentration factor (BCF) of 44, which is a consumption-weighted average based on two data points for oysters and fish that was proposed by the U.S. Environmental Protection Agency in 1980 for broad application to freshwater and marine environments. This BCF is based on the assumption that bioaccumulation is a simple linear function of the exposure concentration. In the nearly quarter of a century since this BCF was promulgated, there have been additions to the arsenic bioaccumulation database and a broader scientific understanding of bioaccumulation mechanisms and how they can be applied to estimating tissue concentrations in aquatic organisms. From this database, we identified 12 studies of arsenic bioaccumulation in freshwater fishes in order to explore differences in laboratory-generated BCFs and field-generated bioaccumulation factors (BAFs) and to assess their relationship to arsenic concentrations in water. Our analysis indicates that arsenic concentrations in tissue and arsenic BAFs may be power functions of arsenic concentration in water. A power function indicates that the highest BCF values may occur at low background levels and may decrease as environmental concentrations increase above the ambient range.     

Hydrogen evolution by co-immobilized Chlorella vulgaris and Clostridium butyricum cells

Whole cells of Chlorella vulgaris and Clostridium butyricum were co-immobilized in 2% agar gel. NADP was suitable as an electron carrier. The rate of hydrogen evolution increased with increasing NADP concentration. The optimum conditions for hydrogen evolution were pH 7.0 and 37°C. The immobilized C. vulgaris-NADP-immobilized Cl. butyricum system continuously evolved hydrogen at a rate of 0.29–1.34 μmol/h per mg Chl for 6 days. On the other hand, the system without NADP evolved only a trace amount of hydrogen.     

Alcohol consumption by youth: Peers,parents, or prices?

Using data from the National Longitudinal Survey of Adolescent to Adult Health, we estimate the effect of peers’ alcohol consumption and alcohol prices on the drinking habits of high-school-age youth. We use the two-stage residual inclusion method to account for the endogeneity of peer drinking in nonlinear models. For our sample of high school students, we find that peer effects are statistically and economically significant regarding the choice to participate in drinking but are not significant for the frequency of drinking, including binge drinking. Regarding alcohol prices, even though we have good price variation in our sample, alcohol prices are not found to be significant. The results are important for policymakers who are considering policies to reduce underage drinking, as we conclude that no significant impact on underage drinking will result from low-tax states’ increasing excise taxes on alcohol so they are similar to those of high-tax states. Policymakers may choose to focus instead on the influence of peers and changing the social norm behavior.     

Self-association of glutamic acid-rich fusion peptide analogs of influenza hemagglutinin in the membrane-mimic environments: Effects of positional difference of glutamic acids on side chain ionization constant and intra- and inter-peptide interactions deduced from NMR and gel electrophoresis measurements

Two glutamic acid-rich fusion peptide analogs of influenza hemagglutinin were synthesized to study the organization of the charged peptides in the membranous media. Fluorescence and gel electrophoresis experiments suggested a loose association between the monomers in the vesicles. A model was built which showed that a positional difference of 3, 7 and 4, 8 results in the exposure of Glu3 and Glu7 side chains to the apolar lipidic core. Supportive results include: first, pK_a values of two pH units higher than reference value in aqueous medium for Glu3 and Glu7 CγH, whereas the deviation of pK_a from the reference value for Glu4 and Glu8 CγH is substantially smaller; second, Hill coefficients of titration shift of these protons indicate anti-cooperativity for Glu3 and Glu7 side chain protons but less so for Glu4 and Glu8, implying a strong electrostatic interaction between Glu3 and Glu7 possibly resulting from their localization in an apolar environment; third, positive and larger titration shift for NH of Glu3 is observed compared to that of Glu4, suggesting stronger hydrogen bond between the NH and the carboxylic group of Glu3 than that of Glu4, consistent with higher degree of exposure to hydrophobic medium for the side chain of Glu3.     

The Redox Biochemistry of Protein Sulfenylation and Sulfinylation

Controlled generation of reactive oxygen species orchestrates numerous physiological signaling events (Finkel, T. (2011) Signal transduction by reactive oxygen species. J. Cell Biol. 194, 7–15). A major cellular target of reactive oxygen species is the thiol side chain (RSH) of Cys, which may assume a wide range of oxidation states (i.e. −2 to +4). Within this context, Cys sulfenic (Cys-SOH) and sulfinic (Cys-SO₂H) acids have emerged as important mechanisms for regulation of protein function. Although this area has been under investigation for over a decade, the scope and biological role of sulfenic/sulfinic acid modifications have been recently expanded with the introduction of new tools for monitoring cysteine oxidation in vitro and directly in cells. This minireview discusses selected recent examples of protein sulfenylation and sulfinylation from the literature, highlighting the role of these post-translational modifications in cell signaling.     

Heart design: free ADP scales with absolute mitochondrial and myofibrillar volumes from mouse to human

Our aim was to estimate a number of bioenergetic parameters in the beating mouse, rat and guinea pig heart in situ and compare the values to those in hearts of mammals over a 2000-fold range in body mass. For the mouse, rat and guinea pig heart, we report a phosphorylation ratio of 1005±50 (n=16), 460±32 (n=10) and 330±22 (n=5) mM⁻¹ and a free cytosolic [ADP] concentration of 13, 18 and 22 μM, respectively. When each parameter was plotted against body mass, they scaled closely to the quarter power (−0.28, r=0.99 and −0.23, r=0.97). A similar regression slope was found when the inverse of free [ADP] was plotted against absolute mitochondrial (slope=−0.26, r=0.99) and myofibrillar volumes (slope=−0.24, r=0.99). The similar slopes indicate that the ratio of absolute mitochondria and myofibrillar volumes in the healthy mammalian heart is a constant, and independent of body size. In conclusion, our study supports the hypothesis that the mammalian heart has a number of highly conserved thermodynamic and kinetic parameters that obey quarter-power laws linking the phosphorylation ratio, ATP turnover rates, free [ADP] and absolute mitochondrial volumes to body size. The results are discussed in terms of possible mechanisms and potential deviations from these laws in some disease states.