NMR studies on unusual DNA conformations adopted by single-strands oligonucleotides

Abstract

Solution structures of several single-strands oligodeoxyribonucleotides were investigated by NMR experiments. Oxytricha telomeric oligonucleotide, $d(G_4T_4G_4)$, showed various solution structure depending on ionic strength and countercation and how the samples were prepared. The reverse-Hoogsteen base-paired simple-foldback structure formed in vitro says that it may be possible model of telomere in vivo. An alternative homo-purine oligonucleotides, $d(AG)_3$ gives a monomeric self-complex stabilized by ionic bonds at low pH in a low ionic solution. As the ionic strength is increased, the oligonucleotides, $d(AG)_3$, showed another form of self-complex at low temperature. Preliminary NOESY experiment showed the possibility of existence of adenine-tetrad.