STRUCTURE OF OLIGONUCLEOTIDES WITH EITHER A STRAND BREAK OR A BULGED NUCLEOTIDE

We report NMR and molecular modelling studies on a DNA duplex structur e which is composed of three oligonucleotides and mimics a strand brea k. Although it retains a B form conformation our model suggests that i t is kinked at the strand break. In the same sequence with an extra bu lged adenosine at the centre for the major species this residue is sta cked in the helix and a kink is observed in the model.