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Vakula N.I.,Moscow State University | Kuramshina G.M.,Moscow State University | Gorb L.G.,Badger Technical Services | Hill F.,U.S. Army | Leszczynski J.,Jackson State University
Chemical Physics Letters | Year: 2013

By employing DFT approaches we studied the adsorption of a single Ag atom and its cation on different sites of a pure α-quartz (0 0 1) surface and on an α-quartz (0 0 1) surface containing an Al defect. The energetically different adsorption sites of Ag and Ag+ were revealed and the profiles of diffusion were calculated. Diffusion of an Ag atom through the pure α-quartz surface is predicted to have a much lower barrier than an Ag cation. However in case of diffusion through the α-quartz surface with an Al defect the barriers are almost the same for both cation and neutral Ag. © 2013 Elsevier B.V. All rights reserved.


Garcia-Reyero N.,Mississippi State University | Ekman D.R.,U.S. Environmental Protection Agency | Habib T.,Badger Technical Services | Villeneuve D.L.,U.S. Environmental Protection Agency | And 4 more authors.
General and Comparative Endocrinology | Year: 2014

Aromatase, a member of the cytochrome P450 superfamily, is a key enzyme in estradiol synthesis that catalyzes the aromatization of androgens into estrogens in ovaries. Here, we used an integrated approach to assess the mechanistic basis of the direct effects of aromatase inhibition, as well as adaptation and recovery processes in fish. We exposed female fathead minnows (. Pimephales promelas) via the water to 30. μg/L of a model aromatase inhibitor, fadrozole, during 8. days (exposure phase). Fish were then held in clean water for 8 more days (recovery phase). Samples were collected at 1, 2, 4, and 8. days of both the exposure and the recovery phases. Transcriptomics, metabolomics, and network inference were used to understand changes and infer connections at the transcript and metabolite level in the ovary. Apical endpoints directly indicative of endocrine function, such as plasma estradiol, testosterone, and vitellogenin levels were also measured. An integrated analysis of the data revealed changes in gene expression consistent with increased testosterone in fadrozole-exposed ovaries. Metabolites such as glycogen and taurine were strongly correlated with increased testosterone levels. Comparison of in vivo and ex vivo steroidogenesis data suggested the accumulation of steroidogenic enzymes, including aromatase, as a mechanism to compensate for aromatase inhibition. © 2013 Elsevier Inc.


Isayev O.,Case Western Reserve University | Isayev O.,U.S. Army | Crespo-Hernandez C.E.,Case Western Reserve University | Gorb L.,Badger Technical Services | And 3 more authors.
Proteins: Structure, Function and Bioinformatics | Year: 2012

Reduction, catalyzed by the bacterial nitroreductases, is the quintessential first step in the biodegradation of a variety of nitroaromatic compounds from contaminated waters and soil. The Enterobacter cloacae nitroreductase (EcNR) enzyme is considered as a prospective biotechnological tool for bioremediation of hazardous nitroaromatic compounds. Using diverse computational methods, we obtain insights into the structural basis of activity and mechanism of its function. We have performed molecular dynamics simulation of EcNR in three different states (free EcNR in oxidized form, fully reduced EcNR with benzoate inhibitor and fully reduced EcNR with nitrobenzene) in explicit solvent and with full electrostatics. Principal Component Analysis (PCA) of the variance-covariance matrix showed that the complexed nitroreductase becomes more flexible overall upon complexation, particularly helix H6, in the vicinity of the binding site. A multiple sequence alignment was also constructed in order to examine positional constraints on substitution in EcNR. Five regions which are highly conserved within the flavin mononucleotide (FMN) binding site were identified. Obtained results and their implications for EcNR functioning are discussed, and new plausible mechanism has been proposed. © 2012 Wiley Periodicals, Inc.


Vasudevan R.,University of Florida | Kennedy A.J.,U.S. Army | Merritt M.,Badger Technical Services | Merritt M.,Emory University | And 2 more authors.
Colloids and Surfaces B: Biointerfaces | Year: 2014

Microscale patterned surfaces have been shown to control the arrangement of bacteria attached to surfaces. This study was conducted to examine the effect of patterned topographies on bacterial fouling using Enterobacter cloacae as the test model. E. cloacae is an opportunistic pathogen involved frequently in nosocomial infections. It is an important model organism to be studied in the context of healthcare associated infections (HAI) and polydimethylsiloxane (PDMS) based urinary catheter fouling. Patterned surfaces, such as Sharklet™, have shown the promise of being a benign surface treatment for prevention of catheter associated urinary tract infections (CAUTI). To the best of our knowledge, inhibition of fouling by E. cloacae has not been demonstrated on microscale patterned PDMS surfaces. In this study, the Sharklet™ and smooth PDMS surfaces were used as controls. All pattern surfaces had statistically significantly lower percentage area coverage compared to the smooth PDMS control. A cross type feature (C-1-PDMS), demonstrated the most significant reduction in percent area coverage, 89% ( p<. 0.01, α= 0.05), compared to the smooth PDMS control and all other patterned test surfaces. Additionally, theoretical calculations show that C-1-PDMS is the only surface predicted to hold the thermodynamically stable Cassie state, which occurs due to trapping air pockets at the liquid-solid interface. Combined the results provide new insights for designing environmentally benign, novel, microscale patterned surfaces for restricting bacterial fouling. © 2014 Elsevier B.V.


Lotufo G.R.,U.S. Army | Biedenbach J.M.,U.S. Army | Sims J.G.,U.S. Army | Chappell P.,Badger Technical Services | And 2 more authors.
Environmental Toxicology and Chemistry | Year: 2015

The manufacturing of explosives and their loading, assembling, and packing into munitions for use in testing on training sites or battlefields has resulted in contamination of terrestrial and aquatic sites that may pose risk to populations of sensitive species. The bioaccumulative potential of the conventional explosives 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and of the insensitive munitions (i.e., less shock sensitive) compound 2,4-dinitroanisole (DNAN) were assessed using the Northern leopard frog, Rana pipiens. Trinitrotoluene entering the organism was readily biotransformed to aminodinitrotoluenes, whereas no transformation products were measured for RDX or DNAN. Uptake clearance rates were relatively slow and similar among compounds (1.32-2.19L kg-1 h-1). Upon transfer to uncontaminated water, elimination rate was very fast, resulting in the prediction of fast time to approach steady state (5h or less) and short elimination half-lives (1.2h or less). A preliminary bioconcentration factor of 0.25L kg-1 was determined for the insensitive munitions compound 3-nitro-1,2,4-trizole-5-one (NTO) indicating negligible bioaccumulative potential. Because of the rapid elimination rate for explosives, tadpoles inhabiting contaminated areas are expected to experience harmful effects only if under constant exposure conditions given that body burdens can rapidly depurate preventing tissue concentrations from persisting at levels that may cause detrimental biological effects. Environ Toxicol Chem 2015;34:880-886. © 2014 SETAC.

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