The Functionality of the three-sited Ferroxidase center of E. coli Bacterial Ferritin (EcFtnA)

At least three ferritins are found in the bacterium Escherichia coli, the heme-containing bacterioferritin (EcBFR) and two non-heme bacterial ferritins (EcFtnA and EcFtnB). In addition to the conserved A- and B-sites of the diiron ferroxidase center, EcFtnA has a third iron-binding site (the C-site) of unknown function that is nearby the diiron site. In the present work, the complex chemistry of iron oxidation and deposition in EcFtnA has been further defined through a combination of oximetry, pH stat, stopped-flow and conventional kinetics, UV-visible, fluorescence and EPR spectroscopic measurements on the wildtype protein and site-directed variants of the A-, B- and C-sites. The data reveal that, while H2O2 is a product of dioxygen reduction in EcFtnA and oxidation occurs with a stoichiometry of Fe(II)/O2 ~ 3:1, most of the H2O2 produced is consumed in subsequent reactions with a 2:1 Fe(II)/H2O2 stoichiometry, thus suppressing hydroxyl radical formation. While the A- and B-sites are essential for rapid iron oxidation, the C-site slows oxidation and suppresses iron turnover at the ferroxidase center. A tyrosyl radical, assigned to Tyr24 near the ferroxidase center, is formed during iron oxidation and its possible significance to the function of the protein is discussed. Taken as a whole, the data indicate that there are multiple iron-oxidation pathways in EcFtnA with O2 and H2O2 as oxidants. Furthermore, the data are inconsistent with the C-site being a transit site, providing iron to the A- and B-sites, and does not support a universal mechanism for iron oxidation in all ferritins as recently proposed

Biomimetic, Mild Chemical Synthesis of CdTe-GSH Quantum Dots with Improved Biocompatibility

Multiple applications of nanotechnology, especially those involving highly fluorescent nanoparticles (NPs) or quantum dots (QDs) have stimulated the research to develop simple, rapid and environmentally friendly protocols for synthesizing NPs exhibiting novel properties and increased biocompatibility

Contrasting vertical and horizontal representations of affect in emotional visual search

The final publication is available at Springer via http://dx.doi.org/ 10.3758/s13423-015-0884-6Independent lines of evidence suggest that the representation of emotional evaluation recruits both vertical and horizontal spatial mappings. These two spatial mappings differ in their experiential origins and their productivity, and available data suggest that they differ in their saliency. Yet, no study has so far compared their relative strength in an attentional orienting reaction time task that affords the simultaneous manifestation of both of them. Here we investigated this question using a visual search task with emotional faces. We presented angry and happy face targets and neutral distracter faces in top, bottom, left, and right locations on the computer screen. Conceptual congruency effects were observed along the vertical dimension supporting the ‘up=good’ metaphor, but not along the horizontal dimension. This asymmetrical processing pattern was observed when faces were presented in a cropped (Experiment 1) and whole (Experiment 2) format. These findings suggest that the ‘up=good’ metaphor is more salient and readily activated than the ‘right=good’ metaphor, and that the former outcompetes the latter when the task context affords the simultaneous activation of both mappings

“The world around me”: The environment and single women

The “environment” has often been taken as a backdrop for feminist research and theory, as a setting within which issues of feminist concern are played out. This environment, however, is not a neutral setting; rather, research over the past 15 years has evidenced the assumptions about “a woman's place” as a man's wife literally built into women's worlds. Space speaks, and the stories it tells center around particular and identifiable assumptions about gender and where a woman “should” be, when, and with whom. Unmarried women are in a unique position in this environment: they are subjected not only to the economic disadvantages and social subjugation of being a woman, but also to the social and economic drawbacks of being single in a couple-oriented society and in an environment they see as not built for them. Although research exists on the sexism in the physical environment, on women's economic and social position, and on singlehood, a need exists to bridge these areas to explore how single women experience their singlehood, their womanhood, and the environment in their everyday lives and decision making. I conducted in-depth interviews with 25 single women, 23 white and 2 African-American women, about their experiences of living single. This article, based on the results of those interviews and a series of focus group discussions, examines how single women negotiate and respond to their necessary environmental decisions about housing, transportation, and leisure activities in an environment not likely to be conducive to their ways of life.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45605/1/11199_2005_Article_BF01544591.pd

Glucose-6-Phosphate Dehydrogenase Protects Escherichia coli from Tellurite-Mediated Oxidative Stress

The tellurium oxyanion tellurite induces oxidative stress in most microorganisms. In Escherichia coli, tellurite exposure results in high levels of oxidized proteins and membrane lipid peroxides, inactivation of oxidation-sensitive enzymes and reduced glutathione content. In this work, we show that tellurite-exposed E. coli exhibits transcriptional activation of the zwf gene, encoding glucose 6-phosphate dehydrogenase (G6PDH), which in turn results in augmented synthesis of reduced nicotinamide adenine dinucleotide phosphate (NADPH). Increased zwf transcription under tellurite stress results mainly from reactive oxygen species (ROS) generation and not from a depletion of cellular glutathione. In addition, the observed increase of G6PDH activity was paralleled by accumulation of glucose-6-phosphate (G6P), suggesting a metabolic flux shift toward the pentose phosphate shunt. Upon zwf overexpression, bacterial cells also show increased levels of antioxidant molecules (NADPH, GSH), better-protected oxidation-sensitive enzymes and decreased amounts of oxidized proteins and membrane lipids. These results suggest that by increasing NADPH content, G6PDH plays an important role in E. coli survival under tellurite stress

Criterion-Related Validity in Multiple-Hurdle Designs: Estimation and Bias

Employee selection often involves a series of sequential tests (or hurdles). However, validation strategies under this complex design are not found in the literature. Missing is a discussion of the statistical properties important in establishing criterion-related validity in multiple-hurdle designs. The authors address this gap in the literature by suggesting a general statistical model for range restriction corrections. Because the multiple-hurdle design includes as special cases predictive and concurrent designs, the corrections apply also to these designs. The general correction model is based on algorithms from the missing data literature. Two missing data procedures are examined: the estimation-maximization procedure and the Bayesian multiple imputation (MI) procedure. These procedures are large-sample equivalent and often yield similar results. The MI procedure, however, has the added advantage of providing easily obtainable standard errors. A hypothetical example of a multiple-hurdle design is used to illustrate the procedures.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline