Defesa química: histórico, classificação dos agentes de guerra e ação dos neurotóxicos

Silva, Gustavo Rocha; Borges, Itamar; Figueroa‐Villar, José Daniel; Castro, Alexandre Taschetto de

doi:10.1590/s0100-40422012001000033

Cited by 35 publications

(28 citation statements)

References 35 publications

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“…Posteriormente, estudamos as duas reações mais comuns no processo de hidrólise alcalina desse agente neurotóxico: a quebra das ligações P-S e P-O 1 47 Apresentamos na Tabela 3 toda a análise termodinâmica na temperatura ambiente (298 K) para as reações H1 e H2. Entretanto, é relatado na literatura que a cinética reacional é desfavorável: 50% de VX é degradado em 78 horas a 295 K.…”

Section: Degradação Do Agente Neurotóxico Vx Por óXido De Magnésiounclassified

Theoretical Chemistry at the Service of the Chemical Defense: Degradation of Nerve Agents in Magnesium Oxide and Hydroxide Surface

Alvim¹,

Vaiss²,

Leitão³

et al. 2014

Revista Virtual De Química

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Abstract:The Pró-Defesa funding of projects was a joint initiative of CAPES and the Ministry of Defense to fund research in defense. In this article we review the main scientific results obtained in the project "Formação de Pessoal Qualificado em Química Quântica Computacional para Atuação na Área de Defesa Química", funded by the first edition of Pró-Defesa in 2005, which involved a collaboration between the Departments of Chemistry of the Federal University of Juiz de Fora and of the Military Institute of Engineering. The main goal of this project was to study, using theoretical-computational methods, the potential of magnesium oxide and hydroxide surfaces to degrade organophosphorus (OP) substances used as warfare agents, also known as neurotoxics. These substances inhibit the acetylcholinesterase, enzyme of fundamental role in the central nervous system. The VX (O-ethyl-S-(2-diisopropylethylamino) ethyl methylphosphonothioate) and sarin (isopropyl methylphosphonofluoridate) agents are some of the main neurotoxic agents, thus the search for ways to degrade them is considerably important. In this paper, we present theoretical investigations of two chemical degradation processes of organophosphates: the hydrolysis of a VX-like OP compound (O,S-dimethyl methylphosphonothioate, DMPT) by the dissociative chemisorption on the MgO(001) surface and the degradation of sarin by a surface of magnesium hydroxide Mg(OH) 2 , known as brucite. These processes were studied by the combination of density functional theory (DFT) with periodic boundary conditions, an approach that is the state of the art of the theoretical methods for this type of problem. In the case of DMPT, we proposed a degradation mechanism that involves degradation reactions of DMPT and water molecules in the presence of two types of MgO(001) surface models: terrace and Al-doped. Conformations, free energy differences, transition states and reaction barriers were calculated. We showed that the MgO(001) surface acts as a possible catalyst for the degradation of VX, but with higher selectivity than the Al-doped surface when compared with sites without defects on the terrace. These results may have important applications as well as to serve as reference for further studies on the decomposition of VX. In the degradation process of sarin using brucite, we proposed four elementary reactions for the global mechanism. We analyzed the adsorption of sarin on the brucite layer through the fluorine and the phosphonyl oxygen atoms (P=O). The two transition states correspond to a hydroxyl anion motion toward the phosphorus atom and to a fluoride moving toward the hydroxyl vacant position; the activation barrier for the rate-limiting step, corresponds to adsorbed sarin attacked by the brucite hydroxyl. The products of the global reaction were an isopropyl methylphosphonate molecule and [Mg(OH) 2−x ]F x . The results of the deactivation process of sarin using a brucite surface show the potential of layered hydroxides to degrade OP compounds. Also the results of this resea...

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Section: Degradação Do Agente Neurotóxico Vx Por óXido De Magnésiounclassified

Theoretical Chemistry at the Service of the Chemical Defense: Degradation of Nerve Agents in Magnesium Oxide and Hydroxide Surface

Alvim¹,

Vaiss²,

Leitão³

et al. 2014

Revista Virtual De Química

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“…7,8 De acordo com a Convenção para Prevenção de Armas Químicas (CPAQ), 9 agentes químicos de guerra são definidos como substâncias químicas, quer gasosas, líquidas ou sólidas, que podem ser utilizadas devido aos seus efeitos tóxicos diretos sobre seres humanos, animais ou plantas. 10 Em um contexto militar, pode-se mencionar dois objetivos básicos para o uso de armas químicas: provocar baixas (mortos e feridos) e diminuir o desempenho operacional das tropas inimigas pela necessidade do uso prolongado de equipamentos de proteção. 10 Devido à facilidade de manufatura e ao baixo custo, as armas químicas passaram do interesse estritamente militar para o de organizações terroristas.…”

Section: Guerra Químicaunclassified

“…10 Em um contexto militar, pode-se mencionar dois objetivos básicos para o uso de armas químicas: provocar baixas (mortos e feridos) e diminuir o desempenho operacional das tropas inimigas pela necessidade do uso prolongado de equipamentos de proteção. 10 Devido à facilidade de manufatura e ao baixo custo, as armas químicas passaram do interesse estritamente militar para o de organizações terroristas. Isso faz com que a defesa contra a guerra química deixe de ser um objeto de preocupação essencialmente militar e torne-se uma preocupação também do meio civil.…”

Section: Guerra Químicaunclassified

Chemical Warfare: Perspectives on Reactivating the Enzyme Acetylcholinesterase Inhibited by Organophosphates

Giacoppo¹,

Lima²,

Kuča³

et al. 2014

Revista Virtual De Química

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Recent attacks on Syria using the nerve agent sarin warned once again the world and the scientists on the use of chemical weapons. It is known that nerve agents are potent inhibitors of acetylcholinesterase (AChE), the enzyme responsible for the hydrolysis of the neurotransmitter acetylcholine and, thus, transmitting of nerve impulses. The process of AChE inhibition by organophosphate (OP) can be reversed by a nucleophile, responsible for dephosphorylation of the residue Ser203 in the active site of the enzyme. In this sense, oximes exhibit this characteristic and are able to remove the neurotoxic and reactivate the enzyme. Here, we review experimental and theoretical results involving docking and quantum mechanical-molecular mechanics hybrid methods (QM/MM), using Molegro® and Spartan® softwares to analyze the interaction of different OPs and oximes with AChE and to evaluate kinetic constants of reactivation.Keywords: Chemical warfare; organophosphates; oximes; docking; QM/MM. ResumoOs ataques recentes na Síria utilizando o agente neurotóxico sarin alertaram mais uma vez a opinião pública mundial e a comunidade científica quanto à utilização de armas químicas. Sabe-se que agentes dos nervos são potentes inibidores da acetilcolinesterase (AChE), enzima responsável pela hidrólise do neurotransmissor acetilcolina e, consequentemente, pela transmissão de impulsos nervosos. A inibição da AChE por um organofosforado (OP) pode ser revertida por um nucleófilo, que desfosforila a Ser203 no sítio ativo da enzima. Nesse sentido, as oximas têm essa característica, pois são capazes de remover o neurotóxico e reativar a enzima. Neste trabalho, revisamos alguns resultados experimentais e teóricos que envolvem estudos de ancoramento molecular e métodos híbrídos quanto-mecânicos/mecânica molecular (QM/MM) usando os softwares Molegro® e Spartan® para analisar as interações de diferentes oximas e OPs com a AChE e avaliar as constantes cinéticas de reativação.Palavras-chave: Guerra química; organofosforados; oximas; ancoramento; QM/MM.

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“…[11][12][13] Degrading, i.e., detoxifying, these agents is challenging 14,15 and analogous dephosphorylation reactions have been efficiently promoted in biological Orth 1761 Vol. 28, No.…”

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confidence: 99%

Degrading Pesticides with Waste Product: Imidazole-Functionalized Rice Husk Catalyst for Organophosphate Detoxification

Ferreira

Orth

2017

J. Braz. Chem. Soc.

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Rice husk (RH) is one the largest agricultural waste products worldwide, and rice is one of the crops that use the most pesticides. Among these, organophosphates have been of increasing concern due to their high toxicity. Herein, we report the functionalization of RH with imidazole groups (RHIMZ) to obtain sustainable catalysts from waste for organophosphate degradation. The waste-derived catalyst showed prominent catalytic activity in dephosphorylation reactions with the model substrate diethyl 2,4-dinitrophenyl phosphate (DENDPP), over 10 5 -fold, compared to the spontaneous reaction (lifetime = 1 month). Finally, RHIMZ was also effective in degrading the pesticide Paraoxon (spontaneous lifetime = 1 million years), degrading 60% in 20 days, giving a 10 7 -fold enhancement. Overall, the proposed approach is environmentally friendly for reusing the waste for a noble cause, i.e., degrading toxic pesticides, which is promising for designing sensors and detoxification processes.Keywords: rice husk, sustainable catalyst, imidazole, pesticide degradation, organophosphate, rice husk functionalization IntroductionRice husk (RH) comprises one of the largest agricultural waste products, with the inherent waste management concerns.1 Notwithstanding, while rice feeds more than half of the human population, about 0.22 kg of RH is produced for each 1 kg of rice cropped, i.e., an estimated production of 164 million tons of RH only in 2013, according to data of FAOSTAT.2,3 Furthermore, RH leads as the most underused cellulosic source in contrast to wood, textile fibers and papers. RH is composed of 75-80% of organic matter, which corresponds nearly to 44% of cellulose, 31% of hemicellulose and 25% of lignin. 4,5 When burned (550-600 °C), RH ash configures as the cereal residue with the highest percentage of Si (94.38, 2.29 and 0.97% of SiO 2 , K 2 O and CaO, respectively, and traces of P 2 O 5 , Al 2 O 3 , MgO, Fe 2 O 3 , Na 2 O and TiO 2 ).5 Despite these facts, research and use of cellulosic residues such as raw RH in the chemical industry is still a relatively unexplored field, thus the main destination of these materials is to burn as biomass or use as fertilizer. 1The RH waste awareness is potentiated by some facts: rice is among the major crops worldwide, which is also one that most applies agrochemicals.6,7 Specifically concerning Brazil's scenario, while it occupies fourth place in worldwide agricultural production, Brazil is one of the largest consumers of agrochemicals. This has become a serious public health issue, since poisoning by pesticides is alarmingly high, losing only to medical drug. Moreover, studies show that nearly 30% of food samples (2011)(2012) contain prohibited substances or are present in abusive amounts.8 This scenario along with the worldwide concern in preventing hunger and assuring safe food has increased the interest in studies regarding reactions with toxic pesticides, especially organophosphates, with potential for developing efficient monitoring and detoxifying procedures. Curiously, abando...

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Defesa química: histórico, classificação dos agentes de guerra e ação dos neurotóxicos

Cited by 35 publications

References 35 publications

Theoretical Chemistry at the Service of the Chemical Defense: Degradation of Nerve Agents in Magnesium Oxide and Hydroxide Surface

Theoretical Chemistry at the Service of the Chemical Defense: Degradation of Nerve Agents in Magnesium Oxide and Hydroxide Surface

Chemical Warfare: Perspectives on Reactivating the Enzyme Acetylcholinesterase Inhibited by Organophosphates

Degrading Pesticides with Waste Product: Imidazole-Functionalized Rice Husk Catalyst for Organophosphate Detoxification

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