Plasmid breakage by 125I-labelled DNA ligands: Effect of DNA-iodine atom distance on breakage efficiency

Abstract

Purpose: The aim of the study is to establish the relationship between the efficiency of DNA double-stranded breakage by 125I-labelled DNA ligands and the distance from the decaying atom to the helical axis. Materials and methods: Two new iodinated minor groove binding ligands were synthesized which, on the basis of molecular modelling studies, place the iodine atom at different distances from the DNA helical axis (namely 7.4 and 11.2 A°). Plasmid DNA breakage experiments, in both buffer-only and buffer + 2M dimethylsulfoxide (DMSO), were used to determine the efficiency of induction of internal double-stranded breaks (DSB) of the two new ligands, as well as that for 125I-Hoechst 33258, whic..