Simplified Method for Quantifying Sulfur Mustard Adducts to Blood Proteins by Ultrahigh Pressure Liquid Chromatography−Isotope Dilution Tandem Mass Spectrometry

A sensitive method for simultaneous screening exposure to 14 alkylating agents based on tripeptide adducts: an efficient approach for chemical weapon verification and chemical impurity profiling in plasma samples

For the implementation of the Chemical Weapons Convention, the Organisation for Prohibition of Chemical Weapons (OPCW) designates laboratories for the analysis of chemicals that can be used as chemical warfare agents (CWAs). In these laboratories, analytical methods for detecting CWAs have been developed for environmental and biomedical samples. Protein adducts from exposed biomedical samples are an important type of biomarker for verification of their abuse. Moreover, these adducts could also be applied in chemical impurity profiling studies of biomedical samples. Alkylating agents, as cytotoxicants, can react with Cys34 in human serum albumin, and cysteine-proline-phenylalanine (CPF) tripeptide adducts generated from proteinase K digestion of modified albumin have been used as biomarkers for retrospective detection of exposure to sulfur mustards or nitrogen mustards. In this study, a sensitive screening method for detecting exposure to 14 alkylating agents in one analytical run was established through sample preparation and instrumental detection optimization. Ultrahigh-performance liquid chromatography-triple quadrupole mass spectrometry (UHPLC-TQ MS) operated in multiple reaction monitoring (MRM) mode and combined with an optimized chromatographic program was used for detecting the 14 corresponding CPF tripeptide adducts. The limits of detection (LODs) are in the range of 0.200-10.0 ng/mL exposure concentrations in human plasma. This method could also allow impurity profiling applicable for potential attribution of sulfur and nitrogen mustard in plasma through retrospective analysis of exposed biomedical samples with impurity compositions as low as 0.1%. This method has potential in clinical diagnosis, CWA verification and forensic identification applications.

Column Screening and Development of HILIC and RPLC Methods Coupled to Tandem Mass Spectrometry for the Monitoring of Albumin on Cysteine 34 Exposed to Mustard Agents

Adduction on protein nucleophile sites by mustard agents can be monitored to assess detection of retrospective exposure to these agents. Cysteine 34 (Cys34) on human serum albumin was selected as the target of choice. This work targets di- and tripeptides adducted on Cys34 by sulfur mustard, sesquimustard, and nitrogen mustards separated in hydrophilic liquid chromatography (HILIC) and Reversed-Phase (RP) mode. The effect of several mobile phase additives on the mass spectrometry (MS) and MS/MS signal and on LC retention profile was studied. A mix of ammonium acetate and acetic acid offered satisfactory results in terms of MS sensitivity. Screening of HILIC columns was performed, and ZIC-HILIC stationary phase was selected for HILIC mode, and C18 stationary phase was used for RP analysis. Negative ionization mode leads to a higher S/N ratio compared to positive ionization mode. Adducted tripeptides were selected for the monitoring of mustard agents' exposure, allowing better sensitivity than their dipeptide homologues. The two developed chromatographic methods have similar sensitivities with LOQs ranging from 1.9 to 20.5 ng/mL for the reversed-phase liquid chromatography (RPLC)-ESI-(-)-MS/MS method and from 1.7 to 43.3 ng/mL for the HILIC-ESI-(-)-MS/MS method. The monitoring method should be selected based on the targeted mustard agent, and the remaining method can be a confirmation tool.

Analytical methods based on liquid chromatography for the analysis of albumin adducts involved in retrospective biomonitoring of exposure to mustard agents

The objective of the present review is to list, describe, compare, and critically analyze the main procedures developed in the last 20 years for the analysis of digested alkylated peptides, resulting from the adduction of albumin by different mustard agents, and that can be used as biomarkers of exposure to these chemical agents. While many biomarkers of sulfur mustard, its analogues, and nitrogen mustards can easily be collected in urine such as their hydrolysis products, albumin adducts require blood or plasma collection to be analyzed. Nonetheless, albumin adducts offer a wider period of detectability in human exposed patients than urine found biomarkers with detection up to 25 days after exposure to the chemical agent. The detection of these digested alkylated peptides of adducted albumin constitutes unambiguous proof of exposure. However, their determination, especially when they are present at very low concentration levels, can be very difficult due to the complexity of the biological matrices. Therefore, numerous sample preparation procedures to extract albumin and to recover alkylated peptides after a digestion step using enzymes have been proposed prior to the analysis of the targeted peptides by liquid chromatography coupled to mass spectrometry method with or without derivatization step. This review describes and compares the numerous procedures including a number of different steps for the extraction and purification of adducted albumin and its digested peptides described in the literature to achieve detection limits for biological samples exposed to sulfur mustard, its analogues, and nitrogen mustards in the ng/mL range.

Ophthalmological aspects of mustard gas poisoning (focus on management)

Background

Amongst the chemical warfare agents, blistering (vesicant) agents can be significant materials. The most important agent in this group is sulfur mustard (mustard gas) which is known as "King of chemical warfare (CW) agents ". Exposure to this agent, seriously causes damages in several organs, such as the eyes. This article reviews the ophthalmological aspects of sulfur mustard with reference of its management.

Methods

A wide-ranging search in PubMed databases, Thomson Reuters and Scopus was done and different aspects of chemical properties of sulfur mustard, its mechanism of action and effects on eyes, clinical finding, diagnostic evaluation, initiate actions, pharmaceutical and surgical interventions was reported.

Results

Sulfur mustard can alkylate DNA and RNA strands and break down structures of protein and lipid of cell membrane. This may impair cell energy production, and leads to cell death. Exposure to sulfur mustard, therefore, causes such problems for organs, including irreversible damage to the eyes.

Conclusion

Understanding the mechanism of the sulfur mustard effect and the early training in prevention injuries will cause fewer complications and damage to organs, including the eyes. Washing the eyes with tap water or eyewash solutions, using mydriatic drops, anti- inflammatory drugs, matrix metalloproteinase inhibitors and antibiotics may help to the management of poisoning. Surgical interventions including tarsorrhaphy, amniotic membrane transplantation, stem cell transplantation and corneal transplantation could reduce the harm to the victims.

A novel approach for the detection and identification of sulfur mustard using liquid chromatography-electrospray ionization-tandem mass spectrometry based on its selective oxidation to sulfur mustard monoxide with N-iodosuccinimide

A new derivatization strategy for the detection and identification of sulfur mustard (HD) via liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) is developed. The method incorporates selective oxidation of the sulfide group by the electrophilic iodine reagent N-iodosuccinimide (NIS) to produce sulfur mustard monoxide (HDSO). The derivatization reaction efficiencies were evaluated with acetonitrile extracts of soil, asphalt, cloth, Formica, and linoleum spiked with HD at concentrations of 50-5000 pg/ml and found to be similar to that with pure acetonitrile. The current derivatization approach is the first to preserve the identity of chloride groups and support HD regulation and evidentiary findings.

Mass spectrometric analysis of adducts of sulfur mustard analogues to human plasma proteins: approach towards chemical provenancing in biomedical samples

The primary aim of this study was to identify biomarkers of exposure to some so-called Schedule 1 sulfur mustard (HD) analogues, in order to facilitate and expedite their retrospective analysis in case of alleged use of such compounds. Since these HD analogues can be regarded as model compounds for possible impurities of HD formed during synthesis processes, the secondary aim was to explore to which extent these biomarkers can be used for chemical provenancing of HD in case biomedical samples are available. While the use of chemical attribution signatures (CAS) for neat chemicals or for environmental samples has been addressed quite frequently, the use of CAS for investigating impurities in biomedical samples has been addressed only scarcely. Human plasma was exposed to each of the five HD analogues. After pronase or proteinase K digestion of precipitated protein and sample work-up, the histidine (His) and tripeptide (CPF) adducts to proteins were analyzed, respectively. Adducts of the analogues could still be unambiguously identified next to the main HD adducts in processed plasma samples after exposure to HD mixed with each of the analogues, at a 1% level relative to HD. In conclusion, we have identified plasma protein adducts of a number of HD analogues, which can be used as biomarkers to assess an exposure to these Schedule 1 chemicals. We have shown that adducts of these analogues can still be analyzed after work-up of plasma samples which had been exposed to these analogues in a mixture with HD, supporting the hypothesis that biomedical sample analysis might be useful for chemical provenancing.

Gas Chromatography-Tandem Mass Spectrometry Verification of Sulfur Mustard Exposure in Humans through the Conversion of Protein Adducts to Free Sulfur Mustard

Exposures to sulfur mustard (HD; bis(2-chloroethyll) sulfide) are well-known to result in the formation of adducts with free aspartate and glutamate residues of plasma proteins (Lawrence, R. J., Smith, J. R., and Capacio, B. R. 2008 32, (1), 31-36). A modified version of the analytical method reported previously for the verification of HD exposure has been developed (Lawrence, R. J., Smith, J. R., and Capacio, B. R. 2008 32, (1), 31-36). The method reported herein involves the reaction of hydrochloric acid with HD-adducted plasma proteins, resulting in the simultaneous cleavage and conversion of the adduct to free HD. A water scavenger, 2,2-dimethoxypropane, was added to the mixture to increase the reaction yield. Deuterated (d₈) thiodiglycol was added as an internal standard and underwent conversion to deuterated sulfur mustard. The analytes were isolated by hexane liquid-liquid extraction and subsequently analyzed by gas chromatography tandem mass spectrometry (GC-MS-MS). An interday and intraday study was performed to evaluate the accuracy and precision of the method. Individual calibration curves with quality control (QC) standards were prepared on 5 days, and a calibration curve with five sets of QCs was prepared on a single day. All results were within the acceptable limits of the validation criteria. Linearity, limit of detection, and limit of quantitation were also verified for each calibration curve. This highly sensitive (pg/mL limit of detection) method can be used for rapid analysis of a definitive marker of sulfur mustard exposure.

Sialic acid on avian erythrocytes

Understanding variation in physiological traits across taxa is a central question in evolutionary biology that has wide-ranging implications in biomedicine, disease ecology, and environmental protection. Sialic acid (Sia), and in particular, 5-N-acetylneuraminic acid (Neu5Ac), is chemically bound to galactose and the underlying glycan via α2-3 or α2-6 glycosidic linkage (i.e., Siaα2-3Galactose or Siaα2-6Galactose), conferring two different cell surface structures that affects cell to cell communication and interactions with foreign agents including microparasites and toxins. As an initial step towards understanding variation of Sia across the class Aves, we collected red blood cells (RBCs or erythrocytes) and measured Sia quantity in 76 species and 340 individuals using HPLC-MS/MS and glycosidic linkage type in 24 species and 105 individuals using hemagglutination assay. Although Sia quantity did not, α2-6 glycosidic linkage did exhibit a discernable phylogenetic pattern as evaluated by a phylogenetic signal (λ) value of 0.7. Sia quantity appeared to be higher in after hatch year birds than hatch year birds (P < 0.05); moreover, ~80% of the measured Sia across all individuals or species was expressed by ~20% of the individuals or species. Lastly, as expected, we detected a minimal presence of 5-N-glycolylneuraminic acid in the avian RBCs tested. These data provide novel insights and a large baseline dataset for further study on the variability of Sia in the class Aves which might be useful for understanding Sia dependent processes in birds.

A quantitative method to detect human exposure to sulfur and nitrogen mustards via protein adducts

Sulfur and nitrogen mustards are internationally banned vesicants listed as Schedule 1 chemical agents in the Chemical Weapons Convention. These compounds are highly reactive electrophiles that form stable adducts to a variety of available amino acid residues on proteins upon exposure. We present a quantitative exposure assay that simultaneously measures agent specific protein adducts to cysteine for sulfur mustard (HD) and three nitrogen mustards (HN1, HN2, and HN3). Proteinase K was added to a serum or plasma sample to digest protein adducts and form the target analyte, the blister agent bound to the tripeptide cysteine-proline-phenylalanine (CPF). The mustard adducted-tripeptide was purified by solid phase extraction and analyzed using isotope dilution LC-MS/MS. Product ion structures were identified using high-resolution product ion scan data for HD-CPF, HN1-CPF, HN2-CPF, and HN3-CPF. Thorough matrix comparison, analyte recovery, ruggedness, and stability studies were incorporated during method validation to produce a robust method. The method demonstrated long term-stability, precision (RSD < 15%), and intra- and inter-day accuracies > 85% across the reportable range of 3.00-200 ng/mL for each analyte. Compared to previously published assays, this method quantitates both sulfur and nitrogen mustard exposure biomarkers, requires only 10 μL of sample volume, and can use either a liquid sample or dried sample spot.

Therapeutic options to treat mustard gas poisoning - Review

Among the blistering (vesicant) chemical warfare agents (CWA), sulfur mustard is the most important since it is known as the "King of chemical warfare agents". The use of sulfur mustard has caused serious damages in several organs, especially the eyes, skin, respiratory, central and peripheral nervous systems after short and long term exposure, incapacitating and even killing people and troops. In this review, chemical properties, mechanism of actions and their effects on each organ, clinical manifestations, diagnostic evaluation of the actions triage, and treatment of injuries have been described.

Rapid analysis of sulfur mustard oxide in plasma using gas chromatography-chemical ionization-mass spectrometry for diagnosis of sulfur mustard exposure

Sulfur mustard (SM) is the most utilized chemical warfare agent in modern history and has caused more casualties than all other chemical weapons combined. SM still poses a threat to civilians globally because of existing stockpiles and ease of production. Exposure to SM causes irritation to the eyes and blistering of skin and respiratory tract. These clinical signs of exposure to SM can take 6-24 h to appear. Therefore, analyzing biomarkers of SM from biological specimens collected from suspected victims is necessary for diagnosis during this latent period. Here, we report a rapid, simple, and direct quantitative analytical method for an important and early SM biomarker, sulfur mustard oxide (SMO). The method includes addition of a stable isotope labeled internal standard, SMO extraction directly into dichloromethane (DCM), rapid drying and reconstitution of the extract, and direct analysis of SMO using gas chromatography-chemical ionization-mass spectrometry. The limit of detection of the method was 0.1 μM, with a linear range from 0.5 to 100 μM. Method selectivity, matrix effect, recovery, and short-term stability were also evaluated. Furthermore, the applicability of the method was tested by analyzing samples from inhalation exposure studies performed in swine. The method was able to detect SMO from 100% of the exposed swine (N = 9), with no interferences present in the plasma of the same swine prior to exposure. The method presented here is the first of its kind to allow for easy and rapid diagnosis of SM poisoning (sample analysis <15 min), especially important during the asymptomatic latency period.

Sampling and analysis of organophosphorus nerve agents: analytical chemistry in international chemical disarmament

Chemistry is a science that contributes to all aspects of our everyday lives and our professions. There are clear examples in law enforcement (forensics) and public health and perhaps less clear (but equally important) uses of chemicals in applications that include automobile manufacturing, electronics, packaging materials, currency printing, and even waste management (recycling and value-added products from garbage). Chemistry can also influence international diplomacy – an area that is likely to be unfamiliar to many chemistry professionals. Take for example the United Nations led investigation into the alleged use of chemical weapons in Syria in August of 2013. Environmental and biomedical samples were collected and analyzed, and they undisputedly confirmed the use of the nerve agent sarin. The results were published in a report by the United Nations Secretary-General and were one of the many influences leading to the accession of The Syrian Arab Republic to the Chemical Weapons Convention (an international treaty prohibiting chemical weapons) and the declaration and dismantlement of a chemical weapons programme. Using this investigation as an example, we highlight some of the chemistry that influenced decision making in a high visibility international event.

Identification of protein adduction using mass spectrometry: Protein adducts as biomarkers and predictors of toxicity mechanisms

The determination of protein-xenobiotic adducts using mass spectrometry is an emerging area which allows detailed understanding of the underlying mechanisms involved in toxicity. These approaches can also be used to reveal potential biomarkers of exposure or toxic response. The following review covers studies of protein adducts resulting from exposure to a wide variety of xenobiotics including organophosphates, polycyclic aromatic hydrocarbons, acetaminophen, alkylating agents and other related compounds.

An improved method for retrospective quantification of sulfur mustard exposure by detection of its albumin adduct using ultra-high pressure liquid chromatography-tandem mass spectrometry

Sulfur mustard (HD) adduct to human serum albumin (ALB) at Cys-34 residue has become an important and long-term retrospective biomarker of HD exposure. Here, a novel, sensitive, and convenient approach for retrospective quantification of HD concentration exposed to plasma was established by detection of the HD-ALB adduct using ultra-high pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) with a novel non-isotope internal standard (IS). The HD-ALB adduct was isolated from HD-exposed plasma with blue Sepharose. The adduct was digested with proteinase K to form sulfur-hydroxyethylthioethyl ([S-HETE])-Cys-Pro-Phe tripeptide biomarker. The tripeptide adduct could be directly analyzed by UHPLC-MS/MS without an additional solid phase extraction (SPE), which was considered as a critical procedure in previous methods. The easily available 2-chloroethyl ethylsulfide (2-CEES) as HD surrogate was first reported to be used as IS in place of traditional d8-HD for quantification of HD exposure. Furthermore, 2-CEES was also confirmed to be a good IS alternative for quantification of HD exposure by investigation of product ion spectra for their corresponding tripeptide adducts which exhibited identical MS/MS fragmentation behaviors. The method was found to be linear between 1.00 and 250 ng•mL(-1) HD exposure (R(2)>0.9989) with precision of <4.50% relative standard deviation (%RSD), accuracy range between 96.5% and 114%, and a calculated limit of detection (LOD) of 0.532 ng•mL(-1). The lowest reportable limit (LRL) is 1.00 ng•mL(-1), over seven times lower than that of the previous method. The entire method required only 0.1 mL of plasma sample and took under 7 h without special sample preparation equipment. It is proven to be a sensitive, simple, and rugged method, which is easily applied in international laboratories to improve the capabilities for the analysis of biomedical samples related to verification of the Chemical Weapon Convention (CWC).