Structure and stability of complexes between poly-5-bromouridylic acid and 2,9-dimethyladenine or 2-methyladenosine.

The complexes formed between poly-5-bromouridylic acid (poly(BU)) and 2,9-dimethyladenine (m2m9A) or 2-methyladenosine (m2Ado) were investigated. The stoichiometry of the m2m9A-poly(BU) complex was found to be 1:1 as determined by equilibrium dialysis measurements. The CD spectra of the complexes showed the formation of helically ordered structure. This is also confirmed by the sharp melting profiles. A comparison of the CD spectra with that of poly(m2A) . poly(BU) complex revealed a close relationship of the helical structures for these three types of complexes. It was observed that the m2m9A was able to form a thermally more stable complex with the poly(BU) than the m2Ado did.