Polysaccharide-Polynucleotide Complexes Part 17. Solvent Effects on Conformational-Transition of Polydeoxyadenylic Acid in the Complexes with Schizophyllan

This paper examines the relationship between the conformation and solvent for the poly(Da)/s-SPG complex using circular dichroism in the 240-300 nm wavelength region. At the low temperature and low salt concentration, poly(Da) in the complex is estimated to take C2′-endo with a different torsional angle from the anti form. With increasing temperature, the circular dichroism (CD) spectrum starts to bear characteristics of C3′-endo and anti as a minority among the majority of C2′-endo and anti. When the salt concentration is increased, the spectrum becomes almost identical to that of the high temperature form under the non-salt condition. Therefore, addition of salt provides the identical effect to increasing temperature. D₂O induces the same effect as decreasing temperature.