Authors: Xiaoxi Ma Jijun Tang Chunzheng Li Qin Liu Jia Chen Hua Li Lei Guo Jianwei Xie
Publish Date: 2014/03/15
Volume: 406, Issue: 21, Pages: 5147-5155
Abstract
Ricin is a toxic protein derived from castor beans and composed of a cytotoxic A chain and a galactosebinding B chain linked by a disulfide bond which can inhibit protein synthesis and cause cell death Owing to its high toxicity ease of preparation and lack of medical countermeasures ricin has been listed as both chemical and biological warfare agents For homeland security or public safety the unambiguous sensitive and rapid methods for identification and quantification of ricin in complicated matrices are of urgent need Mass spectrometric analysis which provides specific and sensitive characterization of protein can be applied to confirm and quantify ricin Here we report a liquid chromatographyelectrospray ionization tandem mass spectrometry LCESIMS/MS method in which ricin was extracted and enriched from serum by immunocapture using antiricin monoclonal antibody 3D74 linked to magnetic beads then digested by trypsin and analyzed by LCESIMS/MS Among 19 distinct peptides observed in LCquadrupole/time of flightMS LCQTOFMS two specific and sensitive peptides T7A 49VGLPINQR56 and T14B 188DNCLTSDSNIR198 were chosen and a highly sensitive determination of ricin was established in LCtriple quadrupoleMS LCQqQMS operating in multiple reaction monitoring mode These specific peptides can definitely distinguish ricin from the homologous protein Ricinus communis agglutinin RCA120 even though the amino acid sequence homology of the Achain of ricin and RCA120 is up to ca 93 and that of Bchain is ca 85 Furthermore peptide T7A was preferred in the quantification of ricin because its sensitivity was at least one order of magnitude higher than that of the peptide T14B Combined with immunocapture enrichment this method provided a limit of detection of ca 25 ng/mL and the limit of quantification was ca 5 ng/mL of ricin in serum respectively Both precision and accuracy of this method were determined and the RSD was less than 15 This established method was then applied to measure ricin in serum samples collected from rats exposed to ricin at the dosage of 50 μg/kg in an intravenous injection manner The results showed that ca 10 ng/mL of the residual ricin in poisoned rats serum could be detected even at 12 h after exposureThis research was supported by grants from the National Natural Science Foundation of China grant nos 21175152 81001262 and 81202248 and National Science and Technology Major Project of the Ministry of Science and Technology of China grant no 2012ZX09301003001010
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