Spin trapping of hydroxyl radicals in biological systems

This chapter discusses the spin trapping of hydroxyl radicals in biological systems. Central to the investigation of the physiological role free radicals play in mediating a number of biological responses is the ability to detect and to characterize these reactive species. When the free radical has a long lifetime, direct electron spin resonance (ESR) spectroscopy can be used to identify this species. However, for unstable free radicals, like superoxide or hydroxyl radical, spin trapping combined with ESR spectroscopy has emerged as one of the most frequently used methods. This technique consists of using a nitrone or nitroso compound to “trap” the initial unstable free radical as a long-lived nitroxide. Under ideal circumstances, independent analytic methods, such as mass spectrometry, allow the correlation of the hyperfine splitting constants of the nitroxide observed with the spin trapping of a specific free radical. However, conditions present in biological systems complicate interpretation of spin trapping data discussed in the chapter.