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ABSTRACT: Experiments were carried out to develop a standard operating procedure for analysis of sulfur mustard adducts to the N-terminal valine in haemoglobin and to explore adduct formation with albumin and keratin. In the first approach, gas chromatography-negative chemical ionization/mass spectrometry (GC-NCI/MS) of the thiohydantoin sample subsequent to the modified Edman degradation was performed using a thermodesorption/cold trap (TCT) injection technique (detection limit for in vitro exposure of human blood to sulfur mustard: 30 nM). In the second approach, the crude thiohydantoin sample was purified by solid-phase extraction procedures. In the third approach, the procedure was shortened significantly by performing the Edman degradation for 2 h at 60 degrees C. Upon exposure of human blood to various concentrations of [14C]sulfur mustard, ca. 20% was covalently bound to albumin. One of the tryptic fragments (T5 containing an alkylated cysteine (HETE-(A-L-V-L-I-A-F-A-Q-Y-L-Q-Q-C-P-F-E-D-H-V-K); MW 2536 Da) could be detected sensitively with liquid chromatography/tandem mass spectrometry analysis (detection limits: > or =15 pg absolute and 1 microM for in vitro exposure of human blood). Upon exposure of human callus (suspensions in 0.9% NaCl; 500 mg ml(-1)) to various concentrations of [14C]sulfur mustard we found 15-20% of the added radioactivity covalently bound to keratin. Upon incubation with base, 80% of the bound radioactivity was split off as [14C]thiodiglycol. This result opens the way for sensitive mass spectrometric detection of sulfur mustard exposure of skin by gas chromatography/mass spectrometry of (derivatized) thiodiglycol.
Journal of Applied Toxicology 12/2000; 20 Suppl 1:S187-92. · 2.48 Impact Factor
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ABSTRACT: The development of procedures for retrospective detection and quantitation of exposure to phosgene, based on adducts to hemoglobin and albumin, is described. Upon incubation of human blood with [(14)C]phosgene (0-750 microM), a significant part of radioactivity (0-13%) became associated with globin and albumin. Upon Pronase digestion of globin, one of the adducts was identified as the pentapeptide O=C-(V-L)-S-P-A, representing amino acid residues 1-5 of alpha-globin, with a hydantoin function between N-terminal valine and leucine. Micro-LC/tandem MS analyses of tryptic as well as V8 protease digests identified one of the adducts to albumin as a urea resulting from intramolecular bridging of lysine residues 195 and 199. The adducted tryptic fragment could be sensitively analyzed by means of micro-LC/tandem MS with multiple-reaction monitoring (MRM), enabling the detection in human blood of an in vitro exposure level of >/=1 microM phosgene.
Chemical Research in Toxicology 08/2000; 13(8):719-26. · 3.78 Impact Factor
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ABSTRACT: The development of a procedure for retrospective detection and quantitation of exposure to the arsenical dichloro(2-chlorovinyl)arsine (lewisite; L1) has been initiated. Upon incubation of human blood with [14C]L1 (20 nM-0.2 mM) in vitro, more than 90% of the total radioactivity was found in the erythrocytes and 25-50% of the radioactivity becomes associated with globin. Evidence was obtained for the presence of several binding sites. One type of binding was identified as L1-induced crosslinking of cysteine residues 93 and 112 of the beta-globin chain. A method was developed for extraction of bound and unbound 2-chlorovinylarsonous acid (CVAA), a major metabolite of L1, from whole blood after treatment with 2,3-dimercapto-1-propanol (BAL). Subsequent to derivatization with heptafluorobutyryl imidazole, the CVAA-BAL derivative could be analysed at a 40-fmol level by means of gas chromatography-mass spectroscopy (GC-MS) under electron impact conditions. With this procedure, in vitro exposure of human blood to 1 nM L1 could be determined. The same procedure was applied to the analysis of human urine samples spiked with CVAA. In vivo exposure of guinea pigs could be established at least 240 h after subcutaneous administration of the agent (0.25 mg/kg) by the determination of bound and unbound CVAA in the blood. In the urine of these animals, CVAA could be detected for 12 h after exposure.
Archive für Toxikologie 08/2000; 74(4-5):207-14. · 4.67 Impact Factor
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ABSTRACT: To develop a mass spectrometric assay for the detection of sulfur mustard adducts with human serum albumin, the following steps were performed: quantitation of the binding of the agent to the protein by using [(14)C]sulfur mustard and analysis of acidic and tryptic digests of albumin from blood after exposure to sulfur mustard for identification of alkylation sites in the protein. The T5 fragment containing an alkylated cysteine could be detected in the tryptic digest with micro-LC/tandem MS analysis. Attempts to decrease the detection limit for in vitro exposure of human blood by analysis of the alkylated T5 fragment were not successful. After Pronase treatment of albumin, S-[2-[(hydroxyethyl)thio]ethyl]Cys-Pro-Phe was analyzed by means of micro-LC/tandem MS, allowing a detection limit for in vitro exposure of human blood of 10 nM, which is 1 order of magnitude lower than that obtained by means of modified Edman degradation. The analytical procedure could be successfully applied to the analysis of albumin samples from Iranian victims of the Iran-Iraq war.
Chemical Research in Toxicology 09/1999; 12(8):715-21. · 3.78 Impact Factor
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ABSTRACT: The stereoselectivity of the phosphonylation reaction and the effects of adduct configuration on the aging process were examined for human acetylcholinesterase (HuAChE) and its selected active center mutants, using the four stereomers of 1,2,2-trimethylpropyl methylphosphonofluoridate (soman). The reactivity of wild type HuAChE toward the PS-soman diastereomers was 4.0-7.5 x 10(4)-fold higher than that toward the PR-diastereomers. Aging of the PSCS-somanyl-HuAChE conjugate was also >1.6 x 10(4)-fold faster than that of the corresponding PRCS-somanyl adduct, as shown by both reactivation and electrospray mass spectrometry (ESI/MS) experiments. On the other hand, both processes exhibited very limited sensitivity to the chirality of the alkoxy group Calpha of either PS- or PR-diastereomers. These stereoselectivities presumably reflect the relative participation of the enzyme in stabilization of the Michaelis complexes and in dealkylation of the respective covalent conjugates, and therefore could be utilized for further probing of the HuAChE active center functional architecture. Reactivities of HuAChE enzymes carrying replacements at the acyl pocket (F295A, F297A, and F295L/F297V) indicate that stereoselectivity with respect to the soman phosphorus chirality depends on the structure of this binding subsite, but this stereoselectivity cannot be explained only by limitation in the capacity to accommodate the PR-diastereomers. In addition, these acyl pocket enzyme mutants display some (5-10-fold) preference for the PRCR-soman over the PRCS-stereomer, while reactivity of the hydrophobic pocket mutant enzyme W86F toward the PRCS-soman resembles that of the wild type HuAChE. Residue substitutions in the H-bond network (E202Q, E450A, Y133F, and Y133A) and the hydrophobic pocket (F338A, W86A, W86F, and Y337A) result in a limited stereoselectivity for the PSCS- over the PSCR-stereomer. Aging of the PS-somanyl conjugates with all the HuAChE mutant enzymes tested practically lacked stereoselectivity with respect to the Calpha of the alkoxy moiety. Thus, the inherent asymmetry of the active center does not seem to affect the rate-determining step of the dealkylation process, possibly because both the PSCS- and the PSCR-somanyl moieties yield the same carbocationic intermediate.
Biochemistry 03/1999; 38(10):3055-66. · 3.42 Impact Factor
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ABSTRACT: In order to initiate a quantitative basis for the toxicology of low level exposure to nerve agents, the toxicokinetics of soman stereoisomers during nose-only exposure for 5 h to 20 ppb (160 microg/m3) of C(+/-)P(+/-)-soman in air were studied in restrained, anesthetized, and atropinized guinea pigs. The concentrations of the toxic C(+/-)P(-)-soman stereoisomers in blood increased according to a biexponential function, after an initial lag time of ca. 30 min for C(+)P(-)-soman, with final concentrations </= 36 pg/ml. It is hypothesized that the lag time is due to binding to carboxylesterases (CaE), partly in the airways prior to systemic uptake. The gradual inhibition of acetylcholinesterase (AChE) in erythrocytes during the exposure appeared to be in satisfactory accordance with the observed levels of the C(+/-)P(-)-soman stereoisomers in blood. Inhibition of AChE in brain and diaphragm is insignificant at the end of the exposure period. This result suggests that neuropsychological disorders are unlikely to develop in this exposure scenario. However, incapacitating miosis due to direct penetration of nerve agent into the eye would probably occur. Our experiments should be reconsidered for exposure of primates, which lack scavenging CaE in their blood. It is argued that the same challenge level in primates might give rise to higher blood levels of C(+/-)P(-)-soman stereoisomers and concomitantly higher inhibition levels of AChE. Therefore, the critical Ct (mg.min/m3) values for nonsystemic effects on eyes and airways and systemic effects might be less divergent than in guinea pigs.
Toxicology and Applied Pharmacology 12/1998; 153(2):179-85. · 4.45 Impact Factor
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ABSTRACT: While non-reactivability of cholinesterases from their phosphyl conjugates (aging) is attributed to an unimolecular process involving loss of alkyl group from the phosphyl moiety, no conclusive evidence is available that this is the only reaction path and involvement of other post-inhibitory processes cannot be ruled out. To address this issue, molecular masses of the bacterially expressed recombinant human acetylcholinesterase and of its conjugates with a homologous series of alkyl methylphosphonofluoridates, were measured by electrospray-ionization mass spectrometry (ESI-MS). The measured mass of the free enzyme was 64,700 Da (calculated 64,695 Da) and those of the methylphosphono-HuAChE adducts, bearing isopropyl, isobutyl, 1,2-dimethylpropyl and 1,2,2-trimethylpropyl substituents, were 64,820, 64,840, 64,852 and 64,860 Da, respectively. These values reflect both the addition of the phosphonyl moiety and the gradual mass increase due to branching of the alkoxy substituent. The composition of these adducts change with time to yield a common product with molecular mass of 64,780 Da which is consistent with dealkylation of the phosphonyl moieties. Furthermore, in the case of 1,2-dimethylpropyl methylphosphono-HuAChE, the change in the molecular mass and the kinetics of non-reactivability appear to occur in parallel indicating that dealkylation is indeed the predominant molecular transformation leading to 'aging' of phosphonyl-AChE adducts.
FEBS Letters 06/1997; 407(3):347-52. · 3.54 Impact Factor
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ABSTRACT: As part of a program to develop methods for the verification of alleged exposure to sulphur mustard, we synthesized and characterized three amino acid adducts presumably formed by alkylation of haemoglobin: 4-(2-hydroxyethylthioethyl)-L-aspartate, 5-(2-hydroxyethylthioethyl)L-glutamate and N1- and N3-(2-hydroxyethylthioethyl)-L-histidine. Suitable derivatization methods for GC/MS analysis were developed for these adducts as well as for the cysteine and the N-terminal valine adduct. Incubation of human blood with [35S]sulfur mustard in vitro followed by acidic hydrolysis of isolated globin and derivatization with Fmoc-Cl afforded three radioactive peaks upon HPLC analysis, one of which coeluted with the synthetic Fmoc derivative of N1/N3-(2-hydroxyethylthioethyl)-L-histidine. After pronase digestion of globin the adducts of histidine, glutamic acid, aspartic acid, cysteine and N-terminal valine could be tentatively identified and quantitated. Final identification was obtained from GC/MS analysis. The most abundant adduct, N1/N3-(2-hydroxyethylthioethyl)-L-histidine, could not be sensitively analysed by GC/MS. A convenient LC-tandem MS procedure was developed for this compound, enabling the detection of exposure of human blood to 10 microM sulphur mustard in vitro.
Archive für Toxikologie 02/1997; 71(3):171-8. · 4.67 Impact Factor
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ABSTRACT: A physiologically based model was developed which describes the in vivo toxicokinetics of the highly reactive nerve agent C(+/-)P(+/-)-soman at doses corresponding to 0.8-6 LD50 in the atropinized guinea pig. The model differentiates between the summated highly toxic C(+/-)P(-)-soman stereoisomers at supralethal doses and the individual nontoxic C(+/-)P(+)-isomers. Several toxicant-specific parameters for the soman stereoisomers were measured in guinea pig tissue homogenates. Cardiac output and blood flow distribution were measured in the atropinized, anesthetized, and artificially ventilated guinea pig. The model was validated by comparison of the time courses for the blood concentrations of the two pairs of stereoisomers in the guinea pig after i.v. bolus administration with the blood concentrations predicted by the model. The predictions put forward for the summated C(+/-)P(-)-isomers are in reasonable agreement with the experimental data obtained after doses corresponding to 2 and 6 LD50. In view of large differences in the rates of hydrolysis of the C(+/-)P(+)-isomers, these two isomers had to be differentiated for satisfactory modeling of both isomers. In order to model the toxicokinetics of C(+/-)P(-)-soman at a dose of 0.8 LD50, the almost instantaneous elimination of the C(+)P(-)-isomer at that dose had to be taken into account. The sensitivity of the predictions of the model to variations in the parameters has been studied with incremental sensitivity analysis. The results of this analysis indicate that extension to a model involving four individual stereoisomers is desirable in view of large differences in the biochemical characteristics of the two C(+/-)P(-)- and C(+/-)P(+)-isomers.
Archive für Toxikologie 02/1997; 71(5):320-31. · 4.67 Impact Factor
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ABSTRACT: Several p-nitrophenyl phosphoramidates with the general formula RO(NH2)P(O)OC6H4-p-NO2, in which R = CH2CH3, CH2CH2F, CH2CHF2, CH2CF3, CH2CH2CH2CH3, and CH2CH2Cl, as well as (NH2)2P(O)OC6H4-p-NO2 were administered intravenously to guinea pigs as pretreatment compounds for protection against the lethal effects of 1,2,2-trimethylpropyl methylphosphonofluoridate (soman) poisoning. Administration of phosphoramidates at a dose that produces 30% acetylcholinesterase (AChE) inhibition in the blood of atropinized guinea pigs at the moment of soman poisoning increases the subcutaneous LD50 of soman up to almost fivefold depending on which compound was used. A synergistic effect with atropine was observed. Three of these compounds offered a higher degree of protection against soman poisoning than pyridostigmine. Furthermore, the surviving animals pretreated with the two phosphoramidates that provided the highest protective ratio were in a better condition at 24 hr after soman intoxication than those pretreated with pyridostigmine. Due to the limited number of compounds and their different characteristics, it appeared difficult to demonstrate a relationship between the rate of spontaneous reactivation of AChE inhibited by the pretreatment compound and the protection against soman. Nevertheless, the results indicate that a several-fold decrease in the rate of spontaneous reactivation relative to that of pyridostigmine may increase the protective ratio against soman.
Toxicology and Applied Pharmacology 11/1996; 140(2):444-50. · 4.45 Impact Factor
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ABSTRACT: In this paper we describe the use of tandem mass spectrometry to identify modified sites in human hemoglobin after in vitro exposure to bis(2-chloroethyl) sulfide (sulfur mustard). Globin isolated from human whole blood which had been exposed to sulfur mustard was degraded with trypsin, and the digests were analyzed by micro LC/MS. Alkylated tryptic fragments (alpha-T1, alpha-T4, alpha-T6, alpha-T9, beta-T1, beta-T9, beta-T10, beta-T11, and beta-T10-S-S-beta-T12) could be tentatively assigned upon comparison with a digest from nonexposed globin. Subsequent tandem mass spectrometry of these peptides allowed unambiguous assignment of 5 specific modified residues: alpha-Val-1, alpha-His-20, beta-Val-1, beta-His-77, and beta-His-97. The results demonstrate the usefulness of microbore LC in combination with tandem mass spectrometry for the structural determination of chemically modified peptides and proteins.
Chemical Research in Toxicology 07/1996; 9(4):781-7. · 3.78 Impact Factor
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ABSTRACT: We report that exposure to the chemical warfare agent sulfur mustard can be monitored by means of a modified Edman degradation involving selective release of the N-terminal valine adduct of hemoglobin with the agent. The degree of alkylation of the N-terminal valine in human hemoglobin is approximately 1-2% of the total alkylation induced in hemoglobin upon treatment of human blood with sulfur mustard. After modified Edman degradation, followed by derivatization with heptafluorobutyric anhydride, the obtained pentafluorophenyl thiohydantion derivative of the valine adduct could be analyzed at a > or = 0.5 fmol level by means of GC/MS under negative ion chemical ionization conditions. Applying this procedure, in vitro exposure of human blood to > or = 0.1 microM of sulfur mustard could be determined. In vivo exposure of guinea pigs could also be established at 48 h after intoxication intravenously with 0.5 mg/kg (0.06 LD50) of the agent.
Chemical Research in Toxicology 06/1996; 9(4):788-92. · 3.78 Impact Factor
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Archive für Toxikologie 02/1996; 70(12):854-5. · 4.67 Impact Factor
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ABSTRACT: Solid-phase synthesis of peptide haptens containing 2-[2-(S-cysteinyl)ethanol has been achieved by solution-phase synthesis of a properly protected S-alkylated cysteine derivative and subsequent solid-phase incorporation.
International journal of peptide and protein research 07/1995; 45(6):497-500.
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ABSTRACT: The fallen concentration of one of the two isomers of soman (1,2,2-trimethylpropyl methylphosphonofluoridate), i.e., C(+)P(-)-soman, was investigated in plasma and in homogenates of brain, lung, liver, kidney, diaphragm, skeletal muscle and mucosa of small intestines from rat, guinea pig and marmoset, and in human plasma (pH 7.5, 37 degrees). The decrease of the isomer concentration was followed by gas chromatographic determination of the residual concentration and proceeded in two phases due to a very rapid saturation of covalent binding sites for the isomer followed by catalysed hydrolysis. Estimates for the concentrations of covalent binding sites were obtained, which were relatively high in liver and kidney. Time periods for the hydrolysis of the isomer from a concentration of 40 ng/mL to 20 ng/mL were evaluated from the second reaction phase. It is concluded that the spontaneous and enzyme-catalyzed hydrolytic activities found for degradation of C(+)P(-)-soman in organs participating in central elimination are sufficiently high to account for the terminal half-life times of the isomer found in our toxicokinetic studies for the blood concentration after intoxication with 2-6 LD50 C(+/-)P(+/-)-soman. The hydrolytic activities are lower in the target organs for toxic action of soman, e.g., diaphragm and brain, especially for guinea pigs and marmosets.
Biochemical Pharmacology 11/1993; 46(8):1413-9. · 4.70 Impact Factor
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ABSTRACT: Immunochemical detection methods have been developed for analysis of protein and DNA adducts of sulfur mustard within our studies performed in collaboration with TNO-Medical Biological Laboratory. In order to validate immunochemical determinations, mass spectrometric detection methods are being developed as an independent, highly sensitive technique having an almost absolute specificity. A method has been developed for specific cleavage of the alkylated N-terminal valine in the alpha-chain of human hemoglobin exposed to sulfur mustard, by using the modified Edman reagent pentafluorophenyl isothiocyanate. After subsequent reaction with heptafluorobutyric anhydride, the derivatized alkylated valine is determined by gas chromatography/negative chemical ionization-mass spectrometry (GC/NCI-MS). In a second approach, a procedure for analysis of the major amino acid adduct formed upon alkylation of hemoglobin with sulfur mustard will be developed. To this end, the protein is alkylated with 35S-sulfur mustard and is subsequently digested by a proteolytic enzyme. After appropriate derivatization of the (alkylated) amino acids in the digest, HPLC analyses with radiometric detection and spiking with synthesized reference adducts and GC/MS analyses are performed in order to show which alkylated amino acids have been formed, and survive digestion. Furthermore, adducted peptides were identified by LC-MS Analysis in a trypsin digest of the alkylated globin.
05/1993;
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ABSTRACT: The confirmed use of chemical agents in the Iran-Iraq conflict and the threat of their use in the recent Gulf War have stressed the need of reliable methods for detection of poisoning with such agents. We have chosen to define exposure to sulfur mustard (HD), based on immunochemical analysis of adducts of HD to DNA and proteins. These adducts are agent-specific and may be stable in vivo for several days or even for months. The detection methods described here are applied to blood samples to establish exposure and-if possible-to estimate internal dose. A major HD-DNA adduct has been identified as N'7-(2'-hydroxyethylthioethyl)-guanine. HD-DNA adducts in nucleated cells of blood treated with 2 micronsM HD are detectable with monoclonal antibodies raised against this monoadduct. recently, the immunochemical assay has been modified to an immunoslot-assay which is more reproducible because of its simplicity. Furthermore, it has at least the same detection limit as observed in the ELISA used previously. Application of immunofluorescence microscopy allows detection down to 0.3 microns M HD (see next paper of this proceedings). The same HD-DNA adduct can also be determined by means of HPLC with electrochemical detection. This method will be used for calibration of the immunochemical assays. Analogous to HD-DNA adducts, reaction products with blood proteins may be used to establish HD exposure. Since it was found that the amino-terminal valine in the a-chain of hemoglobin is alkylated after HD-exposure, the amino- terminal heptapeptide from this protein was synthesized and alkylated with HD.
05/1993;
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ABSTRACT: Concentrations of C(+/-)P(+/-)-soman (1,2,2-trimethylpropyl methylphosphonofluoridate) in urine of anaesthetized, atropinized and artificially ventilated rats, guinea pigs and marmosets were determined 1-4 h after iv administration of 1-6 LD50 of the agent and in the kidneys 1 h after iv administration of 2-6 LD50 14C-C(+/-)P(+/-)-soman. The concentrations of the toxic C(+/-)P(-)-isomers in both urine and kidneys of the rat were at least two orders of magnitude higher than the corresponding levels in the two other species. Relatively high urine concentrations were also found for C(+/-)P(+/-)-soman-intoxicated (6 LD50) rats pretreated with the nontoxic soman analogue PDP (1,2,2-trimethyl dimethylphosphinate), which considerably decreases the persistence of C(+/-)P(-)-soman in rats, or the carboxylesterase inhibitor CBDP [2-(o-cresyl)-4H-1:3:2-benzodioxaphosphorin-2-oxide]. The lethal effect brought about by intravesical administration of C(+/-)P(+/-)-soman in rats showed that the agent can easily be reabsorbed from the bladder. It is concluded, that this reabsorption does probably not explain the previously observed persistence and "late toxicity" of C(+/-)P(+/-)-soman in rats, although the amount of renally excreted C(+/-)P(-)-soman (ca. 1% of the administered dose) should be sufficient for a toxicologically significant effect.
Life Sciences 02/1992; 50(14):1057-62. · 2.53 Impact Factor
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ABSTRACT: Blood levels of the four stereoisomers of the nerve agent C(+/-)P(+/-)-soman were analyzed gas chromatographically in anaesthetized, artificially respirated and atropinized rats, guinea pigs and marmosets at intravenous doses of C(+/-)P(+/-)-soman corresponding with 1-6 LD50. The relatively nontoxic C(+/-)P(+/-)-isomers disappear within a few minutes from the blood stream of all three species, whereas the levels of the highly toxic C(+/-)P(-)-isomers remain toxicologically relevant for periods of 50-100 min in three species of doses of 2-3 LD50. Elimination pathways were quantified using 14C-labeled soman stereoisomers. Whereas the C(+/-)P(+)-isomers are largely eliminated by way of enzymatic hydrolysis, the major elimination pathway for the C(+/-)P(-)-isomers is binding to various proteins, in competition with binding to target acetylcholinesterase. Intraspecies nonlinearity with dose in the toxicokinetics of the C(+/-)P(-)-isomers is related to heterogeneous reactivity of the binding sites. Interspecies nonlinearity is probably due to decreasing amounts of binding sites in the order rats greater than guinea pigs greater than primates, leading to increasing "toxico-availability" in the reversed order.
Neuroscience & Biobehavioral Reviews 02/1991; 15(1):73-7. · 8.65 Impact Factor
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ABSTRACT: Purification of (+)-tabun was accomplished by treatment with electric eel acetylcholinesterase (AChE) in order to bind contaminating (-)-tabun and with purified (+)-tabun shown similar properties in reactivation reactions with oximes (pH 7.5, 25 degrees). The bispyridinium-2,4-dioxime HLö-7 is a substantially active reactivator for these inhibited enzymes as well as for human erythrocyte AChE inhibited with (-)-tabun. In contrast, the corresponding bispyridinium-2-monooxime HI-6 does not show any activity at similar reaction conditions. HLö-7 is also much more active than HI-6 when used as a reactivator for electric eel AChE inhibited by some N-unsubstituted derivatives of tabun. Surprisingly, HLö-7 is highly active in reactivating human erythrocyte and rat diaphragm AChE inhibited by C(+)P(+/-)-and C(-)P(+/-)-soman, i.e. at least as active as HI-6, which is the most potent reactivator for soman-inhibited AChE reported so far. To our knowledge, HLö-7 is the first compound reported in literature that shows a potent reactivating activity towards both tabun-inhibited AChE and soman-inhibited AChE.
Biochemical Pharmacology 03/1989; 38(4):633-40. · 4.70 Impact Factor
