SYNTHETIC POLYNUCLEOTIDES AND ANALOGS AS MODELS FOR STUDIES CONCERNING DNA

This report is divided into three topics, each of them illustrating a different use of synthetic polynucleotides and/or analogues in researc hes concerning DNA. In the first part, NMR studies are described where cyclic oligonucleotides are employed as important tools to improve th e knowledge of the building principles of minihairpin loops. The infor mation thus obtained has been also exploited to design stable four-way junctions from a single strand of DNA. The second part deals with the effects caused by the presence in DNA of the unusual base hmU. It app ears that the substitution of the normal thymine with this base increa ses the local flexibility of double-stranded DNA, thus favouring the i nteraction with type II DNA-binding proteins (DBP II). Finally, result s from various NMR investigations of complexes formed by synthetic dup lexes with distamycin and analogues are presented in the last part.