Synthesis of [14C] Sarin - ResearchGate
21/12/2017 · Synthetic routes for the synthesis of [14C] sarin and related nerve agents are described
Synthesis of n.c.a.[11C]sarin - [PDF Document]
The nerve agents soman, sarin, tabun, and GF are among the most toxic chemicals known (). Minute quantities can be lethal to humans, as demonstrated in the Tokyo subway attack with sarin where 12 persons died and about 5000 were injured (). The great toxicity of these agents has led to restriction of their use for investigational purposes, so that only military laboratories have access to these compounds. Non-military research laboratories must use nerve agent simulants such as diisopropylfluorophosphate, or nerve agent model compounds. We chose to use nerve agent model compounds, whose design suggested they would yield the same covalently modified protein as the true nerve agents. Stereoselective isomers were synthesized because it is known that the cholinesterases react preferentially with specific stereoisomers of nerve agents (-) . The present work tested the hypothesis that model compounds of soman, sarin, tabun, and GF would react with human butyrylcholinesterase to yield adducts identical to those produced by reaction with true nerve agents. This information will determine the choice of model compounds that will yield suitable nerve agent modified proteins for use in the evaluation of biological targets of nerve agents.
Biomarkers of acute sarin exposure can be detected in blood or urine. In blood, the extent of inhibition of RBC AChE is considered the best marker of acute exposure. Sarin preferentially inhibits RBC AChE more than BuChE; however, after high-level sarin exposure, complete inhibition of both esterases occurs (Sidell and Borak, 1992). Since inhibition of blood cholinesterases is a common feature of organophosphates and other anticholinesterases, this biomarker is not specific to sarin exposure. Further, its utility as a biomarker is limited to a short time after exposure, with a return to original blood esterase levels by about 1–3 months (Grob, 1963). The recovery times for blood esterases are somewhat different. BuChE is replaced after about 50 days following de novo synthesis in the liver. RBC AChE recovery is contingent upon the turnover rate of red blood cells, which is about 1 percent per day. This esterase is synthesized with the RBC (Sidell and Borak, 1992). Sensitive methods for detecting urinary metabolites as biomarkers of sarin exposure were recently developed by Japanese researchers in the aftermath of the Tokyo terrorism incident (Minami et al., 1997, 1998).
Enzymatic synthesis of sarin and soman - [PDF Document]
phosphorylated enzyme then can undergo a second process, called aging, by loss of an alkyl group (dealkylation). The half-life for “aging” is about 5 hours after sarin exposure (Sidell and Borak, 1992). Only during this period prior to aging can treatment with oxime therapy (e.g., pralidoxime chloride) successfully remove sarin from the enzyme and thus block the aging process. After aging has occurred, the phosphorylated enzyme (now negatively charged) is resistant to cleavage or hydrolysis and can be considered irreversibly inhibited. Recovery of AChE function occurs only with synthesis of new enzyme. Inhibition of AChE prevents the breakdown of acetylcholine, which accumulates in central and peripheral nerve synapses, leading to the acute cholinergic syndrome.
The goal was to test 14 nerve agent model compounds of soman, sarin, tabun, and cyclohexyl methylphosphonofluoridate (GF) for their suitability as substitutes for true nerve agents. We wanted to know whether the model compounds would form the identical covalent adduct with human butyrylcholinesterase that is produced by reaction with true nerve agents. Nerve agent model compounds containing thiocholine or thiomethyl in place of fluorine or cyanide were synthesized as Sp and Rp stereoisomers. Purified human butyrylcholinesterase was treated with a 45-fold molar excess of nerve agent analog at pH 7.4 for 17 h at 21°C. The protein was denatured by boiling and digested with trypsin. Aged and non-aged active site peptide adducts were quantified by MALDI-TOF mass spectrometry of the tryptic digest mixture. The active site peptides were isolated by HPLC and analyzed by MALDI-TOF-TOF mass spectrometry. Serine 198 of butyrylcholinesterase was covalently modified by all 14 compounds. Thiocholine was the leaving group in all compounds that had thiocholine in place of fluorine or cyanide. Thiomethyl was the leaving group in the GF thiomethyl compounds. However, sarin thiomethyl compounds released either thiomethyl or isopropyl, while soman thiomethyl compounds released either thiomethyl or pinacolyl. Thiocholine compounds reacted more rapidly with butyrylcholinesterase than thiomethyl compounds. Labeling with the model compounds resulted in aged adducts that had lost the O-alkyl group (O-ethyl for tabun, O-cyclohexyl for GF, isopropyl for sarin, and pinacolyl for soman) in addition to the thiocholine or thiomethyl group. The nerve agent model compounds containing thiocholine, and the GF thiomethyl analog were found to be suitable substitutes for true soman, sarin, tabun, and GF in terms of the adduct they produced with human butyrylcholinesterase. However, the soman and sarin thiomethyl compounds yielded two types of adducts, one of which was thiomethyl phosphonate, a modification not found after treatment with authentic soman and sarin.
or it had been used in the sarin synthesis as an acid ..
A number of studies have been performed, which are relevant to the question of whether diazepam has any action in organophosphate poisoning other than as an anticonvulsant. These studies have concentrated on various aspects of the cholinergic system, as well as the GABAergic system and cGMP concentrations. Very large doses of diazepam (20 mg/kg), increased the acetylcholine content of mouse brain (Tonkopii et al., 1978). In the corpus striatum and hippocampus of rats exposed to sarin and soman, diazepam decreased the magnitude of the elevations in choline concentrations, but not those of acetylcholine (Flynn & Wecker, 1986). On the basis of studies on the acetylcholine synthetic system of the mouse brain, Lundgren et al. (1987) suggested that in addition to observed effects on acetylcholine turnover, diazepam might have an effect on choline transport across the blood-brain barrier. Whether diazepam-induced effects on the GABAergic system are responsible for anticonvulsant activity in soman poisoning is unresolved (Lundy et al., 1978). An effect on soman-induced elevations in central nervous cGMP concentrations has been hypothesized as a mechanism of action of the benzodiazepin
Klein AK, Nasr ML, Goldman M. 1987. The effects of in vitro exposure to the neurotoxins sarin (GB) and soman (GD) on unscheduled DNA synthesis by rat hepatocytes. Toxicol Lett 38(3):239–249.
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Soman is synthesized by reacting pinacolyl alcohol with methylphosphonyl difluoride
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Dr. Sarin is an Assistant Professor in the School of Materials Science and Engineering (MSE) at Oklahoma State University. He received his Ph.D. degree in Materials Science and Engineering from University of Illinois at Urbana-Champaign (UIUC). Dr. Sarin has experience in a wide spectrum of materials science research: interdisciplinary as well as core materials research; applied and fundamental; instrumentation and software design/development; biomimetic synthesis; aqueous corrosion; aerospace materials; and even archeological materials from ancient past (6th century B.C.). He has developed novel instrumentation and methods to conduct in-situ investigations of materials at high temperatures (up to 2000°C) in air using synchrotron radiation. His research interests are in fundamental understanding of atomic structure, ordering, crystal chemistry, microstructure and their relationship with material properties in functional ceramic materials. He is particularly interested in developing ceramic materials for applications such as (a) energy conversion (e.g. SOFCs, nuclear fusion/fission reactors, turbines), (b) energy storage (thermoelectrics, batteries, and thermal storage) (c) aerospace (e.g. UHTCs, EBCs, etc.), (d) biomedical (porous ceramic scaffolds for tissue engineering), and (e) water treatment (e.g. multifunctional ultrafiltration membranes). He is a member of the American Ceramic Society, Materials Research Society, and author or co-author of several research articles.
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Sarin is a highly toxic nerve agent produced for chemical warfare. It was synthesized in 1937 in Germany in a quest for improved insecticides (Somani, 1992). Although its battlefield potential was soon recognized, Germany refrained during World War II from using its stockpiles. Sarin’s first military use did not occur until the Iran–Iraq conflict in the 1980s (Brown and Brix, 1998).
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