Constructing a Tandem Mass Spectral Library for Forensic Ricin Identification
Ricin, a protein found in castor seeds, is a lethal toxin that is designated as a category 2 select agent. Because castor seeds are easy to obtain and the toxin can be easily extracted, cases of attempted ricin poisoning are relatively common. A shotgun proteomics method for ricin identification has recently been developed (manuscript in preparation), in which ricin peptides are identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) followed by proteomics database search, and peptide-spectrum matches are verified and compared to standard spectra by a human expert. To make this process more reproducible, objective, and high-throughput, we have created a ricin spectral library for peptide identification to supplement the human review step. To construct these spectral libraries, two pure ricin samples (from a proposed standard reference material) and crude castor seed extracts were digested with trypsin and analyzed using a standard shotgun LC-MS/MS protocol. Spectral libraries were created from the filtered search results from four database search tools. The library was then used in a search using SpectraST on samples from castor seeds. Analysis showed that the spectral library search resulted in more peptides identified from crude castor seed samples compared to MS-GF+ and Sequest plus Percolator. These results suggest that computational comparison of putative ricin peptide spectra to library spectra can be an effective method of confirming the presence of ricin, and that spectral library search may be suitable to augment the more manual and subjective aspects of the currently recommended human expert review.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1608427
- Report Number(s):
- PNNL-SA-142872
- Journal Information:
- Journal of Proteome Research, Vol. 18, Issue 11
- Country of Publication:
- United States
- Language:
- English
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