Anionradicals from 5-halouracil substituted oriented DNA after X-irradiation at low temperatures

Conclusions The model of two initial radiation - induced radical components in oriented fibers of DNA,T ^– andG ⁺ 1], should be amended, for 5-halouracil substituted DNA by the finding that the primary anion is formed on the 5-halouracil base specifically but differentiates, depending on the halogen substituent, into*- and*-forms. The occurrence of the latter appears, from theoretical calculations, to be connected with a C-halogen bond elongation. The DNA matrix apparently allows for this whereas in the corresponding single crystals of 5-bromodeoxyuridine 1] or 5-iododeoxyuridine 4] the crystal packing prevents the elongation thus allowing for*-anion formation only.