title: Detection of ricin in complex samples by immunocapture and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.
abstract: Ricin, the toxin component of Ricinus communis is considered as a potential chemical weapon. Several complementary techniques are required to confirm its presence in environmental samples. Here, we report a method combining immunocapture and analysis by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for the accurate detection of different species of R. communis. Liquid environmental samples were applied to magnetic particles coated with a monoclonal antibody directed against the B-chain of the toxin. After acidic elution, tryptic peptides of the A- and B-chains were obtained by accelerated digestion with trypsin in the presence of acetonitrile. Of the 20 peptides observed by MALDI-TOF MS, three were chosen for detection ( m/ z 1013.6, m/ z 1310.6 and m/ z 1728.9, which correspond to peptides 161-LEQLAGNLR-169, 150-YTFAFGGNYDR-160, and 233-SAPDPSVITLENSWGR-248, respectively). Their selection was based on several parameters such as detection sensitivity, specificity toward ricin forms and absence of isotopic overlap with unrelated peptides. To increase assay reproducibility, stable isotope-labeled peptides were incorporated during the sample preparation phase. The final assay has a limit of detection estimated at approximately 50 ng/mL ( approximately 0.8 nM) of ricin in buffer. No interference was observed when the assay was applied to ricin-spiked milk samples. In addition, several varieties of R. communis or from different geographical origins were also shown to be detectable. The present assay provides a new tool with a total analytical time of approximately 5 h, which is particularly relevant in the context of a bioterrorist incident.
authors.affiliation: CEA, Service de Pharmacologie et d'Immunoanalyse, 91191 Gif-sur-Yvette, France.
authors.forename: Elodie
authors.initials: E
authors.lastname: Duriez
authors.forename: François
authors.initials: F
authors.lastname: Fenaille
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Tabet
authors.forename: Patricia
authors.initials: P
authors.lastname: Lamourette
authors.forename: Didier
authors.initials: D
authors.lastname: Hilaire
authors.forename: François
authors.initials: F
authors.lastname: Becher
authors.forename: Eric
authors.initials: E
authors.lastname: Ezan
mesh_terms: D000595:Amino Acid Sequence; D007887:Fabaceae / Q000737:chemistry; D007118:Immunoassay / Q000379:methods*; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D012276:Ricin / Q000032:analysis*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D014357:Trypsin / Q000737:chemistry
chemical_list: D010455:Peptides; D012276:Ricin; D014357:Trypsin