Reactivity of Trapped Free Radicals in Biological Systems

Abstract

IRRADIATED poly-crystalline amino-acids lend themselves to the kinetic investigation of radical stabilities, because radicals can be induced readily in solid amino-acid by irradiation and because radical concentrations at different temperatures can be followed conveniently by electron spin resonance spectroscopy. In this study, radicals were formed in a number of amino-acids containing sulphur by irradiation at 2537 Å with a low-pressure mercury-vapour germicidal lamp¹. Electron spin resonance spectra were determined on a JEOL–3BX electron spin resonance spectrometer. Samples were usually irradiated continuously at room temperature until the concentration of radicals remained constant and decay rates were then studied at higher temperatures; it was assumed that the radical concentration present was proportional to the signal strength, which was estimated directly from the recorded spectral trace using a planimeter.