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

Stereotypic Behavior and Stable Accident in a 17-year-old Decrepit Part – Arab Stallion

This case describes a stable accident in a 17-year-old part-Arab albino stallion kept in a stall constructed about 30 years ago. Abnormal behaviors like, wood chewing, cribbing and coprophagy were observed and these could be as a result of a distorted gastrointestinal system pH. The body score of the horse was 2. The stallion was found dead with the head trapped in a hay rack. Postmortem result revealed a greenish frothy exudate in the trachea, congested lungs and watery blood.This paper looks into a possible association of abnormal behavioral events in a horse with an increased risk to stable accident in a 30 years old horse facility.Key words: Stable accident, behaviour, pica appetite, hay rack, stereotypic behaviou

Systematic observation of mask adherence and distancing (SOMAD): Findings from Philadelphia

Adherence to guidelines for face coverings and physical distancing are critical strategies to stem the COVID-19 pandemic but are not uniformly followed. Understanding factors associated with adherence to mask-wearing and physical distancing may help guide future control efforts. We conducted an observational study using Systematic Observation of Mask Adherence and Distancing (SOMAD) in August 2020 in parks, playgrounds and commercial streets in each of 10 City Council Districts in Philadelphia, PA. Wearing a mask correctly varied by setting with highest adherence in commercial areas and lowest in playgrounds. Almost 17% wore visible masks that did not cover the nose and/or mouth. There were multiple disparities in correct mask use. Females had higher rates than males (unadjusted relative risk = 1.40, p < .0001) and seniors higher than any other age group (unadjusted chi-square p < .0001). Asians wore masks correctly the most often [adjusted log odds ratio (LOR) = 0.53 compared with non-Hispanic white, p = 0.02]. Correct mask-wearing was higher in areas with a higher population density (adjusted LOR = 0.03 per one thousand/square mile, p = 0.02) and lower in higher poverty areas (adjusted LOR = −0.01, p = .03). Disparities in adherence to mask wearing and physical distancing likely reflect differences in perception of risk by gender, age group, and race/ethnicity. While the risk of COVID-19 transmission is lower in outdoor settings, it is unlikely to be zero. The lower rates of mask use by males and minority groups suggest increased efforts are needed to enhance adherence to recommended guidelines

Functionality of the Three-Site Ferroxidase Center of <i>Escherichia coli</i> Bacterial Ferritin (EcFtnA)

At least three ferritins are found in the bacterium Escherichia coli: the heme-containing bacterioferritin (EcBFR) and two nonheme 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 was further defined through a combination of oximetry, pH stat, stopped-flow and conventional kinetics, UV–vis, fluorescence, and EPR spectroscopic measurements on both the wild-type protein and site-directed variants of the A, B, and C sites. The data reveal that although H₂O₂ is a product of dioxygen reduction in EcFtnA and oxidation occurs with a stoichiometry of Fe²⁺/O₂ ∼ 3:1 most of the H₂O₂ produced is consumed in subsequent reactions with a 2:1 Fe²⁺/H₂O₂ stoichiometry, thus suppressing hydroxyl-radical formation. Although 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, our data do not support a universal mechanism for iron oxidation in all ferritins whereby the C site acts as transit site, as has been recently proposed