TIME-RESOLVED EPR STUDIES ON THE REACTION-RATES OF PEROXYL RADICALS OF POLY(ACRYLIC ACID) AND OF CALF THYMUS DNA WITH GLUTATHIONE - REEXAMINATION OF A RATE-CONSTANT FOR DNA

Electron paramagnetic resonance (EPR) signals of peroxyl radicals of p oly(acrylic acid), PAA, and of single- and double-stranded DNA were ge nerated at 293 K and pH 6.6 by in situ photolysis of O-2-saturated aqu eous solutions containing the macromolecules and H2O2. From time-resol ved EPR measurements upper limits for the rate constants of reaction o f glutathione (GSH) with the peroxyl radicals of PAA [k(b) less than o r equal to(0.8+/-0.2) x 10(2) dm(3)mol(-1)s(-1)] and of single- and do uble-stranded DNA from calf thymus [k(b) less than or equal to(2+/-2)x 10(2) dm(3) mol(-1)s(-1)] were determined. The low value of k(b) for r eaction of GSH with DNA peroxyl radicals is in agreement with the obse rved lack of protective effect of the thiol in radiation-induced DNA s trand break reactions (Liphard ef al. 1990).