NITROXIDE RADICALS, THEIR USE AS METABOLIC PROBES IN BIOLOGICAL MODEL SYSTEMS - AN OVERVIEW

The concept of using a probe, sensitive to the environment, termed >>reporter group<<, arose in the early sixties; readily, nitroxides became the natural candidate for a >>reporter group<<. The term >>reporter group<< was later dismissed and the term spin label or spin probe preferred. The facile synthesis and the multiplicity of compounds which have been coupled to the nitroxide moiety has allowed the development of a number of applications including molecular mobility of proteins and lipids in membranes, study of the enzyme active site and DNA synthesis, measurement of electrical potential, measurement of pH, temperature and oxygen gradients across membranes and, more recently, as contrast agents in magnetic resonance imaging and electron paramagnetic resonance imaging. The overview, by no means comprehensive of the complete literature, aims to give an insight view of nitroxide applications as metabolic probes in the field of biomedical studies reporting methodologies and trying to give a critical view of the procedures and methodologies used.