Radical (chemistry) - Diagnostics

Diagnostics

Free radical diagnostic techniques include:

• Electron spin resonance

A widely used technique for studying free radicals, and other paramagnetic species, is electron spin resonance spectroscopy (ESR). This is alternately referred to as "electron paramagnetic resonance" (EPR) spectroscopy. It is conceptually related to nuclear magnetic resonance, though electrons resonate with higher-frequency fields at a given fixed magnetic field than do most nuclei.

• Nuclear magnetic resonance using a phenomenon called CIDNP
• Chemical labelling

Chemical labelling by quenching with free radicals, e.g. with nitric oxide (NO) or DPPH (2,2-diphenyl-1-picrylhydrazyl), followed by spectroscopic methods like X-ray photoelectron spectroscopy (XPS) or absorption spectroscopy, respectively.

• Use of free radical markers

Stable, specific or non-specific derivates of physiological substances can be measured e.g. lipid peroxidation products (isoprostanes, TBARS), amino acid oxidation products (meta-tyrosine, ortho-tyrosine, hydroxy-Leu, dityrosine etc.), peptide oxidation products (oxidized glutathione - GSSG)

2,2'-Azobis(2-amidinopropane) dihydrochloride (AAPH) is a chemical compound used to study the chemistry of the oxidation of drugs. It is a free radical-generating azo compound. It is gaining prominence as a model oxidant in small molecule and protein therapeutics for its ability to initiate oxidation reactions via both nucleophilic and free radical mechanisms.

• Indirect method

Measurement of the decrease in the amount of antioxidants (e.g. TAS, reduced glutathione - GSH)

• Trapping agents

Using a chemical species that reacts with free radicals to form a stable product that can then be readily measured (Hydroxyl radical and salicylic acid)