Experimental evidence for intramolecular energy transfer in hybrid DNA of B. subtilis after irradiation with long wavelength UV

Investigations on hybrid DNA of B. subtilis after irradiation with long wavelength UV (313 nm) indicate that single strand breaks are produced in the T-strand. These lesions are not observed in normal DNA. Since the action of diffusible photoproducts could be excluded the occurrence of single strand breaks in the T-strand may be due to intramolecular energy transfer. Measuring the breakage rates for the T- and B-strand by employing analytical ultracentrifugation it was found that up to 5% of the energy absorbed in the B-strand can be transferred to the T-strand and causes there single strand breaks. The breakage rates per erg-mm- 2 for single strand breaks after long wavelength UV are determined to be a T = 0.5 · 10 -4 and a B = 10 · 10 -4 breaks/10 6 Dalton for the T- and B-strand of hybrid DNA respectively.