title: Detection and characterisation of radicals in biological materials using EPR methodology.
abstract: BACKGROUND
  Electron paramagnetic resonance (EPR) spectroscopy (also known as electron spin resonance, ESR, spectroscopy) is widely considered to be the "gold standard" for the detection and characterisation of radicals in biological systems.
  
  
  METHODS
  The article reviews the major positive and negative aspects of EPR spectroscopy and discusses how this technique and associated methodologies can be used to maximise useful information, and minimise artefacts, when used in biological studies. Consideration is given to the direct detection of radicals (at both ambient and low temperature), the use of spin trapping and spin scavenging (e.g. reaction with hydroxylamines), the detection of nitric oxide and the detection and quantification of some transition metal ions (particularly iron and copper) and their environment.
  
  
  CONCLUSIONS
  When used with care this technique can provide a wealth of valuable information on the presence of radicals and some transition metal ions in biological systems. It can provide definitive information on the identity of the species present and also information on their concentration, structure, mobility and interactions. It is however a technique that has major limitations and the user needs to understand the various pitfalls and shortcoming of the method to avoid making errors.
  
  
  CONCLUSIONS
  EPR remains the most definitive method of identifying radicals in complex systems and is also a valuable method of examining radical kinetics, concentrations and structure. This article is part of a Special Issue entitled Current methods to study reactive oxygen species - pros and cons and biophysics of membrane proteins. Guest Editor: Christine Winterbourn.
authors.affiliation: The Heart Research Institute, 7 Eliza Street, Newtown, Sydney, NSW 2042, Australia; Faculty of Medicine, Sydney Medical School, Sydney, NSW 2006, Australia.
authors.forename: Clare L
authors.initials: CL
authors.lastname: Hawkins
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Davies
mesh_terms: D000818:Animals; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D005609:Free Radicals / Q000032:analysis*; D006801:Humans; D019097:Spin Trapping / Q000379:methods*
chemical_list: D005609:Free Radicals
keywords: 2-methyl-2-nitrosopropane; 3,5-dibromo-4-nitrosobenzene sulfonic acid; 5,5-dimethyl-1-pyrroline N-oxide; 5-(2,2-dimethyl-1,3-propoxycyclophosphoryl)-5-methyl-1-pyrroline N-oxide; 5-(ethoxycarbonyl)-5-methyl-1-pyrroline N-oxide; 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide; 5-tert-butoxycarbonyl 5-methyl-1-pyrroline N-oxide; BMPO; CYPMPO; DBNBS; DEPMPO; DETC; DMPO; DTCS; EMPO; EPR; ESR; Electron paramagnetic resonance; Hb; MGD; MNP; MS; N-(dithiocarboxy)sarcosine; N-methyl-d-glucamine; N-tert-butyl-α-phenylnitrone; NO(); Nitric oxide; Nitroxide; O(2)(−); PBN; POBN; Radical; SOD; Spin trapping; Superoxide; diethyldithiocarbamate; electron paramagnetic resonance; electron spin resonance; haemoglobin; mass spectrometry; nitric oxide; superoxide dismutase; superoxide radical anion; α-(4-pyridyl-1-oxide)-N-tert-butylnitrone