Application of a trityl-based radical probe for measuring superoxide

Cëcile Rizzi, Alexandre Samouilov, Vijay Kumar Kutala, Narasimham L. Parinandi, Jay L. Zweier, Periannan Kuppusamy

Research output: Contribution to journalArticle


The use of triarylmethyl (trityl) free radical, TAM OX063, for detection of superoxide in aqueous solutions by electron paramagnetic resonance (EPR) spectroscopy was investigated. TAM is paramagnetic (EPR active), highly soluble in water and exhibits a single sharp EPR peak in aqueous media. It is also highly stable in presence of many oxidoreductants such as ascorbate and glutathione that are present in the biological systems. TAM reacts with superoxide with an apparent second order rate constant of 3.1 × 10 3 M-1 s-1. The specific reactivity of TAM with superoxide, which leads to loss of EPR signal, was utilized to detect the generation of superoxide in various chemical (light/riboflavin/electron/donor), enzymatic (xanthine/xanthine oxidase), and cellular (stimulated neutrophils) model systems. The changes in the EPR line-width, induced by molecular oxygen, were utilized in the simultaneous determination of consumption of oxygen in the model systems. The effects of flux of superoxide and concentration of TAM on the efficiency of detection of superoxide were studied. The use of TAM for detection of superoxide offers unique advantages namely, (i) the utilization of very low concentration of the probe, (ii) its stability to bioreduction, and (iii) its use in the simultaneous determination of concentrations of superoxide and oxygen.

Original languageEnglish (US)
Pages (from-to)1608-1618
Number of pages11
JournalFree Radical Biology and Medicine
Issue number12
StatePublished - Dec 15 2003
Externally publishedYes



  • EPR
  • Free radicals
  • Neutrophils
  • Oximetry
  • Riboflavin
  • Spin trapping
  • Superoxide
  • Trityl radical
  • Xanthine oxidase

ASJC Scopus subject areas

  • Medicine(all)
  • Toxicology
  • Clinical Biochemistry

Cite this

Rizzi, C., Samouilov, A., Kumar Kutala, V., Parinandi, N. L., Zweier, J. L., & Kuppusamy, P. (2003). Application of a trityl-based radical probe for measuring superoxide. Free Radical Biology and Medicine, 35(12), 1608-1618.