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Occupational cosmic radiation exposure in Portuguese airline pilots: study of a possible correlation with oxidative biological markers., Silva, Rodrigo, Folgosa Filipe, Soares Paulo, Pereira Alice S., Garcia Raquel, Gestal-Otero Juan Jesus, Tavares Pedro, and Gomes da Silva Marco D. R. , Radiation and environmental biophysics, Jun, Volume 52, Number 2, p.211-220, (2013) AbstractWebsite

Several studies have sought to understand the health effects of occupational exposure to cosmic radiation. However, only few biologic markers or associations with disease outcomes have so far been identified. In the present study, 22 long- and 26 medium-haul male Portuguese airline pilots and 36 factory workers who did not fly regularly were investigated. The two groups were comparable in age and diet, were non-smokers, never treated with ionizing radiation and other factors. Cosmic radiation exposure in pilots was quantified based on direct monitoring of 51 flights within Europe, and from Europe to North and South America, and to Africa. Indirect dose estimates in pilots were performed based on the SIEVERT (Système informatisé d'évaluation par vol de l'exposition au rayonnement cosmique dans les transports aériens) software for 6,039 medium- and 1,366 long-haul flights. Medium-haul pilots had a higher cosmic radiation dose rate than long-haul pilots, that is, 3.3 ± 0.2 μSv/h and 2.7 ± 0.3 μSv/h, respectively. Biological tests for oxidative stress on blood and urine, as appropriate, at two time periods separated by 1 year, included measurements of antioxidant capacity, total protein, ferritin, hemoglobin, creatinine and 8-hydroxy-2-deoxyguanosine (8OHdG). Principal components analysis was used to discriminate between the exposed and unexposed groups based on all the biological tests. According to this analysis, creatinine and 8OHdG levels were different for the pilots and the unexposed group, but no distinctions could be made among the medium- and the long-haul pilots. While hemoglobin levels seem to be comparable between the studied groups, they were directly correlated with ferritin values, which were lower for the airline pilots.

Bacterioferritin from Desulfovibrio vulgaris Hildenborough is a functional DPS-like enzyme, Folgosa, F., Timóteo C. G., Guilherme M., Penas D., Tavares P., and Pereira A. S. , FEBS JOURNAL, Sep, Volume {279}, Number {1, SI}, p.{465}, (2012) Abstract
Synthesis of catecholamine conjugates with nitrogen-centered bionucleophiles, Siopa, Filipa, Pereira Alice S., Ferreira Luisa M., Matilde Marques M., and Branco Paula S. , BIOORGANIC CHEMISTRY, Oct, Volume {44}, 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA, p.{19-24}, (2012) Abstract

The enzymatic (tyrosinase) and chemical (NaIO4, Ag2O or Fremys's salt) oxidation of biologically relevant catecholamines, such as dopamine (DA), N-acetyldopamine (NADA) and the Ecstasy metabolites (alpha-MeDA and N-Me-alpha-MeDA) generates the corresponding o-quinone which can be trapped with nitrogen bionucleophiles such as N-acetyl-histidine and imidazole in a regioselective reaction that takes place predominantly at the 6-position of the catecholamine. (C) 2012 Elsevier Inc. All rights reserved.

Desulfovibrio vulgaris bacterioferritin uses H2O2 as a co-substrate for iron oxidation and reveals DPS-like DNA protection and binding activities, Timoteo, Cristina G., Guilherme Marcia, Penas Daniela, Folgosa Filipe, Tavares Pedro, and Pereira Alice S. , BIOCHEMICAL JOURNAL, Volume {446}, Number {1}, p.{125-133}, (2012) Abstract

A gene encoding Bfr (bacterioferritin) was identified and isolated from the genome of Desulfovibrio vulgaris cells, and overexpressed in Escherichia coli. In vitro, H2O2 oxidizes Fe2+ ions at much higher reaction rates than O-2. The H2O2 oxidation of two Fe2+ ions was proven by Mossbauer spectroscopy of rapid freeze-quenched samples. On the basis of the Mossbauer parameters of the intermediate species we propose that D. vulgaris Bfr follows a mineralization mechanism similar to the one reported for vertebrate H-type ferritins subunits, in which a diferrous centre at the ferroxidase site is oxidized to diferric intermediate species, that are subsequently translocated into the inner nanocavity. D. vulgaris recombinant Bfr oxidizes and stores up to 600 iron atoms per protein. This Bfr is able to bind DNA and protect it against hydroxyl radical and DNase deleterious effects. The use of H2O2 as an oxidant, combined with the DNA binding and protection activities, seems to indicate a DPS (DNA-binding protein from starved cells)-like role for D. vulgaris Bfr.

Spectroscopic Evidence for and Characterization of a Trinuclear Ferroxidase Center in Bacterial Ferritin from Desulfovibrio vulgaris Hildenborough, Pereira, Alice S., Timoteo Cristina G., Guilherme Marcia, Folgosa Filipe, Naik Sunil G., Duarte Americo G., Huynh Boi Hanh, and Tavares Pedro , Journal Of The American Chemical Society, Volume {134}, Number {26}, p.{10822-10832}, (2012) Abstract

Ferritins are ubiquitous and can be found in practically all organisms that utilize Fe. They are composed of 24 subunits forming a hollow sphere with an inner cavity of similar to 80 angstrom in diameter. The main function of ferritin is to oxidize the cytotoxic Fe2+ ions and store the oxidized Fe in the inner cavity. It has been established that the initial step of rapid oxidation of Fe2+ (ferroxidation) by H-type ferritins, found in vertebrates, occurs at a diiron binding center, termed the ferroxidase center. In bacterial ferritins, however, X-ray crystallographic evidence and amino acid sequence analysis revealed a trinuclear Fe binding center comprising a binuclear Fe binding center (sites A and B), homologous to the ferroxidase center of H-type ferritin, and an adjacent mononuclear Fe binding site (site C). In an effort to obtain further evidence supporting the presence of a trinuclear Fe binding center in bacterial ferritins and to gain information on the states of the iron bound to the trinuclear center, bacterial ferritin from Desulfovibrio vulgaris (DvFtn) and its E130A variant was loaded with substoichiometric amounts of Fe2+, and the products were characterized by Mossbauer and EPR spectroscopy. Four distinct Fe species were identified: a paramagnetic diferrous species, a diamagnetic diferrous species, a mixed valence Fe2+Fe3+ species, and a mononuclear Fe2+ species. The latter three species were detected in the wild-type DvFtn, while the paramagnetic diferrous species was detected in the E130A variant. These observations can be rationally explained by the presence of a trinuclear Fe binding center, and the four Fe species can be properly assigned to the three Fe binding sites. Further, our spectroscopic data suggest that (1) the fully occupied trinuclear center supports an all ferrous state, (2) sites B and C are bridged by a mu-OH group forming a diiron subcenter within the trinuclear center, and (3) this subcenter can afford both a mixed valence Fe2+Fe3+ state and a diferrous state. Mechanistic insights provided by these new findings are discussed and a minimal mechanistic scheme involving O-O bond cleavage is proposed.