Detecting Ricin

When it comes to monitoring for a bioterrorist attack with the lethal toxin ricin, two things are important: unequivocally identifying the ricin protein and determining whether or not it's active. A method developed by Suzanne R. Kalb and John R. Barr of the Centers for Disease Control & Prevention combines those goals into a series of tests capable of smoothly identifying and characterizing the toxin, which does its damage by cleaving purine from ribosomal RNA to halt protein synthesis (Anal. Chem., DOI: 10.1021/ac802769s). Working with milk, apple juice, human blood serum, and saliva samples spiked with ricin, the researchers extracted the toxic protein from the liquids by first mixing in magnetic beads coated with ricin-specific antibodies. They then reacted the bead-bound protein with a DNA substrate that mimics ricin's natural target and analyzed the products for purine cleavage through matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Finally, the scientists eluted ricin from the beads, enzymatically digested the protein, and used LC/MS/MS to identify the toxin. The method is sensitive and selective, and it could be adapted to identify other protein toxins, the researchers say.