UNIT 17.7 Immuno-Spin Trapping: Detection of Protein-Centered Radicals

  1. Dario C. Ramirez,
  2. Ronald P. Mason

Published Online: 1 JUN 2005

DOI: 10.1002/0471140856.tx1707s24

Current Protocols in Toxicology

Current Protocols in Toxicology

How to Cite

Ramirez, D. C. and Mason, R. P. 2005. Immuno-Spin Trapping: Detection of Protein-Centered Radicals. Current Protocols in Toxicology. 24:17.7:17.7.1–17.7.18.

Author Information

  1. National Institute of Environmental Health Science, National Institutes of Health, Research Triangle Park, North Carolina

Publication History

  1. Published Online: 1 JUN 2005
  2. Published Print: MAY 2005


Protein-centered radicals are involved in biological oxidative damage induced by drugs, environmental hazards, and cellular reactive oxygen species. Presently, the technique most widely used to study protein-centered radicals is electron spin resonance (ESR; also known as electron paramagnetic resonance, EPR); used either directly or in combination with the spin-trapping technique. Protein-centered radicals may be trapped with the nitrone spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) forming DMPO-radical adducts. However, after a few minutes these adducts decay, often by oxidation to DMPO-protein radical–derived nitrone adducts, which are ESR-silent species. Because nitrone adducts are not free radicals and their formation involves the creation of a covalent linkage, they are stable long after the ESR signal decays. In the new alternative technique of immuno-spin trapping, nitrone adducts are detected by using an antibody, i.e., anti-DMPO, that recognizes their nitrone moiety. Immuno-spin trapping is a simple, reliable, affordable, sensitive, and specific approach to detecting protein-centered radicals, and its development brings the power of immunoassays to bear on the field of toxicology of free radical–mediated biological damage.


  • oxidative damage;
  • protein-centered radical;
  • DMPO-protein radical–derived nitrone adduct;
  • immuno-spin trapping