Constructing a Tandem Mass Spectral Library for Forensic Ricin Identification
Isabelle O'Bryon1, Abigail E Tucker1, Brooke L D Kaiser1
1Chemical and Biological Signature Sciences Group , Pacific Northwest National Laboratory , Richland , Washington 99354 , United States.
Journal of Proteome Research
|October 1, 2019
Summary
This study introduces a novel spectral library search method for detecting ricin, a lethal toxin from castor seeds. This approach enhances ricin identification in forensic samples, offering a more familiar technique for practitioners.
Area of Science:
- Forensic toxicology
- Proteomics
- Mass spectrometry
Background:
- Ricin, a lethal protein toxin from castor seeds, is a Category 2 select agent with common attempted poisoning cases.
- Current detection methods for ricin often rely on targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS), which may be unfamiliar to some forensic practitioners.
- Untargeted proteomics methods, while effective, are less commonly used in forensic practice.
Purpose of the Study:
- To propose and validate a spectral library search method for identifying ricin peptides.
- To adapt spectral library search, a technique familiar in small molecule identification, for protein toxin analysis in forensic science.
- To provide a more accessible and potentially more effective method for ricin detection in forensic casework.
Main Methods:
- Construction of spectral libraries using tryptic peptides from two pure ricin samples (including a reference material).
- Analysis of ricin peptides via standard shotgun LC-MS/MS protocols.
- Application of spectral library search (using SpectraST) on forensically realistic castor seed extracts prepared by crude methods.
Main Results:
- Spectral library search identified more tryptic ricin peptides in crude castor seed samples compared to MS-GF+ and Sequest plus Percolator database searches.
- This represents the first published use of spectral library search for detecting protein toxins in forensic samples.
- The method demonstrated effective computational comparison of peptide spectra against a library for ricin identification.
Conclusions:
- Spectral library search is a viable and effective method for detecting ricin in forensic samples.
- This approach offers a potentially more familiar and sensitive technique for forensic scientists compared to traditional untargeted proteomics.
- The findings support the use of spectral libraries as a key element for authentic standard comparison in forensic toxin analysis.
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