RESUMEN
In this study, Staphylococcus aureus biofilms, which are considered a foe for being pathogenic, were tested for their uranium bioremediation capacity to find out if they can turn out to be a friend. Acid phosphatase activity, which is speculated to aid in bio-precipitation of U(VI) from uranyl nitrate solution, was assayed in biofilms of seven different S. aureus strains. The presence of acid phosphatase enzyme was detected in the biofilms of all S. aureus strains (in the range of 3.1 ± 0.21 to 26.90 ± 2.32 µi.u./g), and found to be higher when compared to that of their planktonic phenotypes. Among all, S. aureus V329 biofilm showed highest biofilm formation ability along with maximum phosphatase activity (26.9 ± 2.32 µi.u./g of biomass). Addition of phosphate enhanced the U(VI) remediation when treated with uranyl nitrate solution. S. aureus V329 biofilm showed significant U tolerance with only a 3-log reduction when exposed to 10 ppm U(VI) for 1 h. When treated in batch mode, V329 biofilm successfully remediated up to 47% of the 10 ppm U(VI). This new approach using the acid phosphatase from the S. aureus V329 biofilm presents an alternative method for the remediation of uranium contamination.
Asunto(s)
Fosfatasa Ácida/química , Biopelículas , Restauración y Remediación Ambiental/métodos , Staphylococcus aureus/enzimología , Uranio , Biodegradación Ambiental , Plancton/química , Nitrato de Uranilo/químicaRESUMEN
Cyclic peptides with two phosphoserines and two glutamic acids were developed to mimic high-affinity binding sites for uranyl found in proteins such as osteopontin, which is believed to be a privileged target of this ion in vivo. These peptides adopt a ß-sheet structure that allows the coordination of the latter amino acid side chains in the equatorial plane of the dioxo uranyl cation. Complementary spectroscopic and analytical methods revealed that these cyclic peptides are efficient uranyl chelating peptides with a large contribution from the phosphorylated residues. The conditional affinity constants were measured by following fluorescence tryptophan quenching and are larger than 10(10) at physiological pH. These compounds are therefore promising models for understanding uranyl chelation by proteins, which is relevant to this actinide ion toxicity.
Asunto(s)
Quelantes/química , Imitación Molecular , Péptidos Cíclicos/química , Fosfopéptidos/química , Nitrato de Uranilo/química , Secuencia de Aminoácidos , Sitios de Unión , Calcio/química , Quelantes/síntesis química , Dicroismo Circular , Ácido Glutámico/química , Iminoácidos , Osteopontina/química , Péptidos Cíclicos/síntesis química , Fosfopéptidos/síntesis química , Fosfoserina/química , Estructura Secundaria de Proteína , Espectrometría de Masa por Ionización de Electrospray , Triptófano/químicaRESUMEN
The use of phosphate mineral products in animal nutrition, as a major source of phosphor and calcium, can lead to uranium entering the food chain. The aim of the present study was to determine the protective effect of natural sepiolite and sepiolite treated with acid for broilers after oral intake of uranium. The broilers were contaminated for 7 days with 25 mg/uranyl nitrate per day. Two different adsorbents (natural sepiolite and sepiolite treated with acid) were given via gastric tube immediately after the oral administration of uranium. Natural sepiolite reduced uranium distribution by 57% in kidney, 80% in liver, 42% in brain, and 56% in muscle. A lower protective effect was observed after the administration of sepiolite treated with acid, resulting in significant damage of intestinal villi in the form of shortening, fragmentation, and necrosis, and histopathological lesions on kidney in the form of edema and abruption of epithelial cells in tubules. When broilers received only sepiolite treated with acid (no uranyl nitrate), shortening of intestinal villi occurred. Kidney injuries were evident when uranium concentrations in kidney were 0.88 and 1.25 µg/g dry weight. It is concluded that adding of natural sepiolite to the diets of broilers can reduce uranium distribution in organs by significant amount without adverse side effects.
Asunto(s)
Alimentación Animal/análisis , Pollos , Silicatos de Magnesio/química , Uranio/química , Adsorción , Animales , Concentración de Iones de Hidrógeno , Mucosa Intestinal/metabolismo , Factores de Tiempo , Uranio/aislamiento & purificación , Uranio/metabolismo , Uranio/toxicidad , Nitrato de Uranilo/químicaRESUMEN
It is demonstrated that hydroxyl radicals and hydrogen peroxide are formed under the action of uranyl ions in aqueous solutions containing no reducing agents. In the presence of uranyl ions, formation of 8-oxoguanine in DNA and long-lived protein radicals are observed in vitro. It is shown that the pro-oxidant properties of uranyl at micromolar concentrations mostly result from the physico-chemical nature of the compound rather than its radioactive decay. Uranyl ions lead to damage in DNA and proteins causing death of HEp-2 cells by necrotic pathway. It is revealed that the uranyl ions enhance radiation-induced oxidative stress and significantly increase a death rate of mice exposed to sublethal doses of X-rays.
Asunto(s)
Especies Reactivas de Oxígeno/química , Uranio/química , Uranio/toxicidad , Animales , Proteínas Sanguíneas/química , Médula Ósea/efectos de los fármacos , Médula Ósea/efectos de la radiación , Daño del ADN/efectos de los fármacos , Guanina/análogos & derivados , Calor , Peróxido de Hidrógeno/química , Radical Hidroxilo/análisis , Iones , Rayos Láser , Masculino , Ratones , Mortalidad , Pruebas de Mutagenicidad , Nitrato de Uranilo/química , Rayos XRESUMEN
Photooxidation and consequent cleavage of oligodeoxynucleotides by the uranyl ion is greatly enhanced in the presence of a terminal 5'- or 3'-phosphate group. This enhanced cleavage is confined to nearby phosphodiester bonds in the case of a 5'-phosphate, but is less localized in the case of a 3'-phosphate. Several attempts to use a complementary oligodeoxynucleotide to direct a uranyl "warhead" against an oligodeoxynucleotide target were unsuccessful. Our results are most easily explained if we suppose that uranyl ions form coordination complexes with terminal phosphates and that, on photoexcitation, coordinated uranyl ions extract a hydrogen atom from the CH bond of a nearby deoxyribose residue.