Identification of RIP-II toxins by affinity enrichment, enzymatic digestion and LC-MS

Anal Chem. 2015 Jan 20;87(2):967-74. doi: 10.1021/ac5032918. Epub 2014 Dec 26.

Abstract

Type 2 ribosome-inactivating protein toxins (RIP-II toxins) were enriched and purified prior to enzymatic digestion and LC-MS analysis. The enrichment of the RIP-II family of plant proteins, such as ricin, abrin, viscumin, and volkensin was based on their affinity for galactosyl moieties. A macroporous chromatographic material was modified with a galactose-terminated substituent and packed into miniaturized columns that were used in a chromatographic system to achieve up to 1000-fold toxin enrichment. The galactose affinity of the RIP-II proteins enabled their selective enrichment from water, beverages, and extracts of powder and wipe samples. The enriched fractions were digested with trypsin and RIP-II peptides were identified based on accurate mass LC-MS data. Their identities were unambiguously confirmed by LC-MS/MS product ion scans of peptides unique to each of the toxins. The LC-MS detection limit achieved for ricin target peptides was 10 amol and the corresponding detection limit for the full method was 10 fmol/mL (0.6 ng/mL). The affinity enrichment method was applied to samples from a forensic investigation into a case involving the illegal production of ricin and abrin toxins.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Abrin / analysis
  • Abrin / isolation & purification
  • Abrin / metabolism
  • Adult
  • Chromatography, Affinity / methods*
  • Chromatography, Liquid / methods*
  • Galactose / metabolism*
  • Humans
  • Male
  • Peptide Fragments / analysis
  • Plant Extracts / chemistry*
  • Ribosome Inactivating Proteins, Type 2 / analysis*
  • Ribosome Inactivating Proteins, Type 2 / isolation & purification
  • Ribosome Inactivating Proteins, Type 2 / metabolism
  • Ricin / analysis
  • Ricin / isolation & purification
  • Ricin / metabolism
  • Tandem Mass Spectrometry / methods*
  • Toxins, Biological / analysis
  • Toxins, Biological / isolation & purification
  • Toxins, Biological / metabolism
  • Trypsin / metabolism*

Substances

  • Peptide Fragments
  • Plant Extracts
  • Ribosome Inactivating Proteins, Type 2
  • Toxins, Biological
  • mistletoe lectin I
  • Abrin
  • Ricin
  • volkensin
  • Trypsin
  • Galactose