SIMULTANEOUS MULTISITE EPR SPECTROSCOPY IN-VIVO

A gradient technique to measure electron paramagnetic resonance spectr a simultaneously at several different locations is described. The tech nique is based on the use of point probes containing paramagnetic cent ers. The value of the magnetic field gradient is chosen to be sufficie nt to separate the EPR signals from the different paramagnetic probes yet at the same time small enough to change only minimally the shape o f individual signals. The conditions to apply this technique are consi dered in detail. When experimental data have a high signal-to-noise ra tio, the lineshape distortion induced by the gradient can be corrected with the aid of a known distribution function of paramagnetic centers within the probe. The maximum entropy deconvolution algorithm is succ essfully applied for the correction of significantly distorted lines. The technique is experimentally tested and applied to measure the conc entration of oxygen in hypertrophied rat myocardium and normal rat kid ney in vivo by low frequency EPR (L-band, 1.2 GHz). Two types of EPR o xygen-sensitive probes-lithium phthalocyanine crystals and synthetic c arbohydrate chars-were used.