Ricin is a highly toxic protein toxin that poses a potential bioterrorism threat due to its potency and widespread availability. It is included in the list of chemicals prohibited by the Chemical Weapons Convention (CWC) and the Biological Weapons Convention (BWC). However, the accurate quantification of ricin through absolute mass spectrometry (MS) using a protein standard absolute quantification (PSAQ) strategy is not widely practiced.
In a new study, researchers develop a novel approach for the absolute quantification of ricin in complex matrices using recombinant single-chain and full-length mutant ricin as the protein internal standard, instead of isotope-labeled ricin, in conjunction with ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS).
To simplify protein expression, the A-chain and B-chain of the ricin mutant internal standard (RMIS) were directly linked to replace the original interchain disulfide bonds.
By employing internal protein standards, this quantitative strategy overcomes the challenges posed by variations in extraction recoveries, matrix effects, and digestion efficiency encountered when working with different matrices. The method was thoroughly validated using a milk matrix.
A protein standard absolute quantification strategy for enhanced absolute quantification of ricin in complex matrices using in vitro synthesized mutant holoprotein as internal standard by ultra-high-performance liquid chromatography-tandem mass spectrometry. Journal of Chromatography A, 11 October 2023.