Production of UV-generated hydroxyl free radicals imaged by proton-electron double-resonance imaging with spin trapping

Oxygenderived free radicals such as hydroxyl ( * OH) and superoxide (0; . ) have
been implicated as causes of tissue damage in many disease states ( 1). The ability to
image and measure the production of these and other free radicals in vivo would have
profound implications for many areas of biological and medical research. While these
free radicals themselves are too short-lived for direct detection, they are amenable to
a technique called spin trapping, in which short-lived radicals are stabilized prior to
detection by EPR (2). In this work we have combined spin trapping with protonelectron double-resonance imaging (PEDRI) and have for the first time imaged the
production of hydroxyl radicals, in this case formed by the ultraviolet irradiation of
aqueous solutions of hydrogen peroxide.