Detection of the kinetics of biochemical reactions with oxygen using exchange broadening in the ESR spectra of nitroxide radicals.

To detect changes in the oxygen concentration during biochemical reactions, the exchange broadening in the ESR spectra of nitroxide radicals caused by the dissolved oxygen, has been used. The measurements have been carried out using changes in the width either of the proton hyperfine structure components or of the nitrogen hyperfine structure line with an unresolved proton structure. Detection of mitochondrial respiration in a volume of about 10(-3) cm 3 and respiration for 100 +/- 5 liver cells in a volume of about 10(-4) cm3 has been carried out.