Effects of Oxygen and Sulphydryl-containing Compounds on Irradiated Transforming DNA. III. Reaction Rates

Summary

The absolute rate for the repair reaction of radiation-induced, oxygen-dependent lesions in bacterial transforming DNA with the sulphydryl (SH)-containing compound dithiothreitol (DTT) has been determined using a fast response method, the gas explosion technique, to be 1·6 × 10⁶ dm³ mol⁻¹ s⁻¹. Glutathione reacts ten times slower than DTT with the irradiated transforming DNA. It can also be calculated that transforming DNA radicals react with O₂ in a damage-fixing reaction with a rate of about 3 × 10⁸ dm³ mol⁻¹ s⁻¹. These rates are compared with values in the literature for reaction rates of SH, compounds and O₂ with irradiated DNA constituents and with bacterial cells.