ADVANCES IN SPIN LABEL OXIMETRY

Spin label oximetry is defined as the use of nitroxide radical spin labels to monitor oxygen transport. Bimolecular collisions of oxygen with spin labels alter both the longitudinal and transverse relaxation times of the spin label. Various experimental approaches can be used to observe these effects. Two of these are discussed here. (1) Saturation—recovery time—domain ESR using high observing power, rather than, as is customary, a low value, is shown to improve the sensitivity to bimolecular collisions with oxygen. First results obtained with a recently constructed S—band saturation—recovery apparatus are presented. (2) The use of electron-electron double resonance (ELDOR) as an oxygen sensitive display is considered. It is found to have substantial advantages over continuous wave (CW) saturation studies. Because it is instrumentally a simpler technique than saturation recovery, it can be useful in laboratories where acquisition of pulse equipment is unrealistic. © 1990 De Gruyter