INTERACTION AND ASSOCIATION OF BASES AND NUCLEOSIDES IN AQUEOUS SOLUTIONS .4. PROPERTIES OF 7-METHYLINOSINE AS RELATED TO NATURE OF STACKING INTERACTION

In a continuing study on the nature and the mechanism of association of nucleosides in aqueous solution, the properties of 7-methylinosine were investigated extensively. The results in pmr and conductance studies have supported the betaine-type structure of this molecule proposed previously. Therefore, this molecule is highly polar because of the deficiency of electrons in the five-membered ring and the excess of electrons in the six-membered ring. The vapor pressure osmometry data and the pmr results both indicate that this polar 7-methylinosine does not associate in water more than inosine or 1-methylinosine. This comparative study suggests that the electrostatic interaction of monopoles and dipoles of the bases does not contribute significantly to the stacking interaction of nucleosides in aqueous solution. A model for the stacking of 7-methylinosine is proposed based on pmr data. Concepts about the nature of the association of the nucleosides by stacking are proposed and discussed on the basis f current findings. Owing to the unusual structure of 7-methylinosine other properties of this molecule have also been investigated by pmr and uv absorption spectroscopy. © 1969, American Chemical Society. All rights reserved.