Cloning, sequencing, and characterization of the hexahydro-1,3,5-trinitro-1,3,5-triazine degradation gene cluster from Rhodococcus rhodochrous

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a high explosive which presents an environmental hazard as a major land and groundwater contaminant. Rhodococcus rhodochrous strain 11Y was isolated from explosive contaminated land and is capable of degrading RDX when provided as the sole source of nitrogen for growth. Products of RDX degradation in resting-cell incubations were analyzed and found to include nitrite, formaldehyde, and formate. No ammonium was excreted into the medium, and no dead-end metabolites were observed. The gene responsible for the degradation of RDX in strain 11Y is a constitutively expressed cytochrome P450-like gene, xpLA, which is found in a gene cluster with an adrenodoxin reductase homologue, xplB. The cytochrome P450 also has a flavodoxin domain at the N terminus. This study is the first to present a gene which has been identified as being responsible for RDX biodegradation. The mechanism of action of XplA on RDX is thought to involve initial denitration followed by spontaneous ring cleavage and mineralization

Thermal Decomposition of Energetic Materials by ReaxFF Reactive Molecular Dynamics

We report the study of thermal decomposition of 1,3,5-trinitrohexahydro-s-triazine (RDX) bonded with polyurethane (Estane) and of the bulk hydrazine by molecular dynamics (MD) simulations equipped with the reactive force field (ReaxFF). For the polymer binder explosive, the simulation results show that the thermal decomposition of RDX is affected by the presence of the polymer binder Estane. Generally, with addition of Estane the decomposition of RDX slows down. Final products including N2, H2O, CO, CO2 and intermediates NO2, NO and HONO have been identified from the thermal decomposition processes. For the bulk hydrazine, it is found that with the increase of temperature, its decomposition increases and more N2 and H2 are generated, but NH3 molecules are consumed much faster at higher temperatures. This simulation work provides us an approach to quickly test the response of various energetic materials to thermal conditions

Application of introduced nano-diamonds for the study of carbon condensation during detonation of high explosives

This paper describes the experimental studies of the formation of nano-diamonds during detonation of TNT/RDX 50/50 mixture with small-angle x-ray scattering (SAXS) method at a synchrotron radiation beam on VEPP-3 accelerator. A new experimental method with introduction of nano-diamonds into the explosive has been applied. Inclusion of the diamonds obtained after detonation into the TNT and RDX explosives allows modelling of the case of instant creation of nano-diamonds during detonation.Comment: Latex, 4 pages, 2 figures (proc. of SR-2008

Evaluation of a TiO2 photocatalysis treatment on nitrophenols and nitramines contaminated plant wastewaters by solid-phase extraction coupled with ESI HPLC–MS

Nitration reactions of aromatic compounds are commonly involved in different industrial processes for pharmaceutical, pesticide or military uses. For many years, most of the manufacturing sites used lagooning systems to treat their process effluents. In view of a photocatalytic degradation assay, the wastewater of a lagoon was investigated by using HPLC coupled with mass spectrometry. The wastewater was highly concentrated in RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), HMX (octahydro- 1,3,5,7-tetranitro-1,3,5,7-tetrazocine) and two herbicides Dinoterb (2-tert-butyl-4,6-dinitrophenol) and Dinoseb (2-sec-butyl-4,6-dinitrophenol). First of all, an analytical method using solid-phase extraction (SPE) combined with HPLC ESI MS/MS was put in work for identification and titration of RDX, HMX and the two dinitrophenols in a complex natural matrix. Then, the UV/TiO2 treatment was investigated for pollutants removal. Dinitrophenolic compoundswere significantly degraded after a 8-h-exposition of the wastewater/TiO2 suspension, whereas RDX and HMX were poorly affected

Thermodynamic Simulation of the RDX-Aluminum Interface Using ReaxFF Molecular Dynamics

We use reactive molecular dynamics (RMD) simulations to study the interface between cyclotrimethylene trinitramine (RDX) and aluminum (Al) with different oxide layers to elucidate the effect of nanosized Al on thermal decomposition of RDX. A published ReaxFF force field for C/H/N/O elements was retrained to incorporate Al interactions and then used in RMD simulations to characterize compound energetic materials. We find that the predicted adsorption energies for RDX on the Al(111) surface and the apparent activation energies of RDX and RDX/Al are in agreement with ab initio calculations. The Al(111) surface-assisted decomposition of RDX occurs spontaneously without potential barriers, but the decomposition rate becomes slow when compared with that for RDX powder. We also find that the Al(111) surface with an oxide layer (Al oxide) slightly increases the potential barriers for decomposition of RDX molecules, while α-Al_2O_3(0001) retards thermal decomposition of RDX, due to the changes in thermal decomposition kinetics. The most likely mechanism for the thermal decomposition of RDX powder is described by the Avrami–Erofeev equation, with n = 3/4, as random nucleation and subsequent growth model. Although the decomposition mechanism of RDX molecules in the RDX/Al matrix complies with three-dimensional diffusion, Jander’s equation for RDX(210)/Al oxide and the Zhuralev–Lesokin–Tempelman (Z-L-T) equation for RDX(210)/Al_2O_3(0001) provide a more accurate description. We conclude that the origin of these differences in dynamic behavior is due to the variations in the oxide layer morphologies

MicroRNA and messenger RNA profiling reveals new biomarkers and mechanisms for RDX induced neurotoxicity

Background RDX is a well-known pollutant to induce neurotoxicity. MicroRNAs (miRNA) and messenger RNA (mRNA) profiles are useful tools for toxicogenomics studies. It is worthy to integrate MiRNA and mRNA expression data to understand RDX-induced neurotoxicity. Results Rats were treated with or without RDX for 48 h. Both miRNA and mRNA profiles were conducted using brain tissues. Nine miRNAs were significantly regulated by RDX. Of these, 6 and 3 miRNAs were up- and down-regulated respectively. The putative target genes of RDX-regulated miRNAs were highly nervous system function genes and pathways enriched. Fifteen differentially genes altered by RDX from mRNA profiles were the putative targets of regulated miRNAs. The induction of miR-71, miR-27ab, miR-98, and miR-135a expression by RDX, could reduce the expression of the genes POLE4, C5ORF13, SULF1 and ROCK2, and eventually induce neurotoxicity. Over-expression of miR-27ab, or reduction of the expression of unknown miRNAs by RDX, could up-regulate HMGCR expression and contribute to neurotoxicity. RDX regulated immune and inflammation response miRNAs and genes could contribute to RDX- induced neurotoxicity and other toxicities as well as animal defending reaction response to RDX exposure. Conclusions Our results demonstrate that integrating miRNA and mRNA profiles is valuable to indentify novel biomarkers and molecular mechanisms for RDX-induced neurological disorder and neurotoxicity.published_or_final_versio