Ricin, a plant-derived toxin extracted from the seeds of Ricinus communis (castor bean plant), is one of the most toxic proteins known. Ricin's high toxicity, widespread availability, and ease of its extraction make it a potential agent for bioterrorist attacks. Most ricin detection methods are based on immunoassays. These methods may suffer from low efficiency in matrices containing interfering substances, or from false positive results due to antibody cross reactivity, with highly homologous proteins. In this study, we have developed a simple, rapid, sensitive, and selective mass spectrometry assay, for the identification of ricin in complex environmental samples. This assay involves three main stages: (a) Ricin affinity capture by commercial lactamyl-agarose (LA) beads. (b) Tryptic digestion. (c) LC-MS/MS (MRM) analysis of tryptic fragments. The assay was validated using 60 diverse environmental samples such as soil, asphalt, and vegetation, taken from various geographic regions. The assay's selectivity was established in the presence of high concentrations of competing lectin interferences. Based on our findings, we have defined strict criteria for unambiguous identification of ricin. Our novel method, which combines affinity capture beads followed by MRM-based analysis, enabled the identification of 1 ppb ricin spiked into complex environmental matrices. This methodology has the potential to be extended for the identification of ricin in body fluids from individuals exposed (deliberately or accidentally) to the toxin, contaminated food or for the detection of the entire family of RIP-II toxins, by applying multiplex format.

中文翻译：

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使用LC-MS / MS（MRM）基于内酰胺基琼脂糖珠快速，灵敏地鉴定环境样品中的蓖麻毒素。

蓖麻毒素是一种从植物蓖麻种子中提取的植物毒素，是已知毒性最高的蛋白质之一。蓖麻毒素的高毒性，广泛的可利用性和易提取性使其成为生物恐怖袭击的潜在诱因。大多数蓖麻毒素检测方法是基于免疫测定的。这些方法可能会在含有干扰物质的基质中效率低下，或者由于与高同源蛋白的抗体交叉反应而导致假阳性结果。在这项研究中，我们开发了一种简单，快速，灵敏和选择性的质谱分析方法，用于鉴定复杂环境样品中的蓖麻毒素。该测定涉及三个主要阶段：（a）通过商业内酰胺基琼脂糖（LA）珠捕获蓖麻毒素亲和力。（b）胰蛋白酶消化。（c）胰蛋白酶片段的LC-MS / MS（MRM）分析。使用从不同地理区域采集的60种不同的环境样本（例如土壤，沥青和植被）对测定进行了验证。该测定的选择性是在存在高浓度竞争性凝集素干扰物的情况下建立的。根据我们的发现，我们为蓖麻毒素的明确鉴定定义了严格的标准。我们的新方法结合了亲和捕获珠，然后进行了基于MRM的分析，从而能够鉴定加标到复杂环境基质中的1 ppb蓖麻毒蛋白。通过应用多重格式，该方法具有扩展的潜力，可用于识别（有意或无意）接触毒素，受污染食品的个体的体液中的蓖麻毒素，或用于检测整个RIP-II毒素家族。